An X-ray and Infrared Survey of the Lynds 1228 Cloud Core

The nearby Lynds 1228 (L1228) dark cloud at a distance of ~200 pc is known to harbor several young stars including the driving sources of the giant HH 199 and HH 200 Herbig-Haro outflows. L1228 has been previously studied at optical, infrared, and radio wavelengths but not in X-rays. We present results of a sensitive 37 ks Chandra ACIS-I X-ray observation of the L1228 core region. Chandra detected 60 X-ray sources, most of which are faint (<40 counts) and non-variable. Infrared counterparts were identified for 53 of the 60 X-ray sources using archival data from 2MASS, Spitzer, and WISE. Object classes were assigned using mid-IR colors for those objects with complete photometry, most of which were found to have colors consistent with extragalactic background sources. Seven young stellar object (YSO) candidates were identified including the class I protostar HH 200-IRS which was detected as a faint hard X-ray source. No X-ray emission was detected from the luminous protostar HH 199-IRS. We summarize the X-ray and infrared properties of the detected sources and provide IR spectral energy distribution modeling of high-interest objects including the protostars driving the HH outflows.Comment: 38 pages, 7 tables, 8 figures; to appear in A

The Parson to the Plankton: George Israel Playfair (1871–1922)

It is one hundred years since ‘the late G.I. Playfair, Australia’s foremost student of freshwater algae’ died, in Tauranga, New Zealand, but the value of his collection, and descriptions of many freshwater photosynthetic organisms from New South Wales, is current and growing

Oxide ion transport and phase stability in the excess oxygen scheelite phases

Oxide ion conductors for use in electrochemical devices such as solid oxide fuel cells and electrolysers are typically viewed as requiring three-dimensional isotropic structures that will promote ion transport. The majority of materials considered as electrolytes in devices are based on either the fluorite or perovskite structure types. An essential feature of the materials is that they will accommodate a range of oxygen lattice defects, typically through cation substitution, that introduces vacancies to maintain charge neutrality, and it is the presence and mobility of these defects that produce fast oxide ion conductors. An alternative that has only recently been explored is the potential for oxygen interstitial species to provide fast ion transport pathways. Initially studies focussed on anisotropic materials such as the layered perovskites as potential electrode materials, but more recently our studies have focussed on new electrolyte families. Please click Additional Files below to see the full abstract

X-ray emission from an FU Ori star in early outburst: HBC 722

Aims: We conducted the first X-ray observations of the newly erupting FU Ori-type outburst in HBC 722 (V2493 Cyg) with the aim to characterize its X-ray behavior and near-stellar environment during early outburst. Methods: We used data from the XMM-Newton and Chandra X-ray observatories to measure X-ray source temperatures and luminosities as well as the gas column densities along the line of sight toward the source. Results: We report a Chandra X-ray detection of HBC 722 with an X-ray luminosity of LX ~ 4E30 erg s-1. The gas column density exceeds values expected from optical extinction and standard gas-to-dust ratios. We conclude that dust-free gas masses are present around the star, such as strong winds launched from the inner disk, or massive accretion columns. A tentative detection obtained by XMM-Newton two years earlier after an initial optical peak revealed a fainter X-ray source with only weak absorption.Comment: Accepted for Astronomy & Astrophysics Letters on September 17, 201

Synthesis and characterisation of metal oxides and metal doped variants

The 57Fe Mössbauer spectra recorded from inverse spinel related Fe3O4 below the Verwey transition temperature are best interpreted in terms of tetrahedral A sites and two non-equivalent octahedral B sites. The broadening of the 57Fe Mössbauer spectra recorded from Fe3O4 at 298K is associated with the superposition of the two components arising from the non-equivalent sites as opposed to an electron hopping process. The unit cell size of the metal-doped ferrite, Fe3-xSnxO4, 0 4+ ions substitute exclusively on the octahedral B sites of the inverse spinel related Fe3O4 structure. The amount of Fe2+ present in the Fe3O4 increases as the tin content increases in a fashion consistent with charge balance being maintained by reduction of Fe3+ on either the A or B sites. The Curie temperature of Fe3-xSnxO4 decreases with increasing tin content. Exsolution of tin from the Fe3O4 structure after prolonged heating at elevated temperatures in vacuo has also been observed. Oxidation of tin-doped magnetite involves a transformation to structurally related tin-doped maghemite before undergoing a structural transformation to tin-doped hematite. A lowering of the Curie temperature for both the tin-doped maghemite and and tin-doped hematite has been identified. Chromium- and gallium- doped magnetite have also been found to have considerably lower Curie temperatures than pure magnetite. Cubic-, tetragonal- and monoclinic- zirconium(IV) oxides have been produced by boiling zirconium (IV) acetate under reflux and calcining at increasing temperatures. Raman spectroscopy has been used to distinguish between tetragonal- and cubic- zirconia. Addition of HCl to the initial solution suppresses the formation of the tetragonal and cubic phases. Addition of ammonia to the initial solution produces tetragonal and cubic phases. Addition of ammonia to the initial solution produces tetragonal zirconia which remains stable to 900°C. Hydrothermal synthesis of zirconium(IV) oxide from a solution of ziroconium(IV) acetate produces a mixture of tetragonal- and monoclinic- zirconia. Increasing the calcination temperature induces a transformation to the monoclinic polymorph. Addition of HCl to the initial solution gives monoclinic zirconia via an oxychloride phase. Addition of aqueous ammonia to the initial solution stabilises the tetragonal phase at temperatures up to 900°C. Tetragonal iron-doped zirconia has been synthesised from iron(II) acetate and zirconium(IV) acetate by boiling under reflux. Increasing calcination temperature induces a transformation to the monoclinic phase. Increasing pH stabilises the tetragonal phase against transformation to monoclinic zirconia. Iron segregates from the zirconia structure at temperatures exceeding 900°C. Hydrothermal processing of iron(II) acetate and zirconium(IV) acetate produces a mixture of tetragonal- and monoclinic- iron-doped zirconia. Calcination at 900°C induces the segregation of iron from the zirconia structure. Tetragonal iron-doped zirconia is characterised by a large quadrupole splitting in the 57Fe Mössbauer spectrum

College Student Changing Attitudes and Beliefs About the Nature of and Teaching of Mathematics and Science

With an estimated 17.3 million STEM jobs in the US, there exists a need for a STEMready workforce that is science literate with positive attitudes and beliefs toward the learning and teaching of mathematics and science (Graf, Fry, & Funk, 2018). However, the US has seen a steady decline in the number of high school students interested in STEM-related fields with only 16% of interested students with proven proficiency in mathematics and science and are ready to enroll in college STEM programs (ACT, 2017; Osborne & Dillon, 2008; Stake & Mares, 2001). With the decline in student interest, the US has fallen behind both China and India in the production of a STEM-ready workforce (Herman, 2018). To address the need for students to enroll in STEM-related fields, students need positive attitudes toward the learning and teaching of mathematics and science. Colleges and universities can increase positive attitudes and beliefs in students by immersing students in reformed science courses that utilize active learning practices such as experiential learning and modeling. The study uses quantitative data analysis on a linear data set collected over twelve years, 2002 – 2013, through the use of a survey tool to collect pre- and post-survey data on students’ attitudes and beliefs toward the nature of and the teaching of mathematics and science. The study focuses on two groups of students in two different reformed physics courses at a large midsouth research university; pre-service elementary education majors and physics and engineer majors. Pre-service education majors are students in training who have yet to undertake any teaching and are required to enroll in the Physics for Elementary Teachers course, an integrated lecture and lab course that meets three times a week for 110 minutes each time. The physics and engineer majors complete a calculus-based sequence of courses, University Physics I and II, that meets twice a week for a one-hour lecture and twice a week for a two-hour lab. This study was guided by wanting to know to what extent are there significant differences in the change (pre- and post-test) in the attitudes and beliefs about the nature of and teaching of mathematics and science for students who have completed a one- or two-semester sequence of a reformed science course. The survey tool used in the study was The Attitudes and Beliefs about the Nature of and Teaching of Mathematics and Science Survey. Study findings show that pre-service education students had very little change, remaining slightly higher than neutral, on attitudes and beliefs toward understanding the nature of science but, had significant changes toward teaching mathematics and science. Science students demonstrated significant positive changes in attitude toward understanding the nature of science but, had low attitudes towards learning to teach mathematics and science. The results of the study show that reformed science courses, as measured by a TROP observation, ties into Kolb’s cycle on experiential learning with modeling as a reformed active learning practice in science labs, has an impact on student attitudes and beliefs