Interpreting the Hydrogen IR Lines - Impact of Improved Electron Collision Data

We evaluate the effect of variations in the electron-impact excitation cross sections on the non-LTE line formation for hydrogen in early-type stars. While the Balmer lines are basically unaffected by the choice of atomic data, the Brackett and Pfund series members allow us to discriminate between the different models. Non-LTE calculations based on the widely-used approximations of Mihalas, Heasley & Auer and of Johnson fail to simultaneously reproduce the observed optical and IR spectra over the entire parameter range. Instead, we recommend a reference model using data from ab-initio calculations up to principal quantum number n<=7 for quantitative work. This model is of general interest due to the ubiquity of the hydrogen spectrum.Comment: 6 pages, 6 figure

Ferroelectric Materials for Solar Energy Conversion: Photoferroics Revisited

The application of ferroelectric materials (i.e. solids that exhibit spontaneous electric polarisation) in solar cells has a long and controversial history. This includes the first observations of the anomalous photovoltaic effect (APE) and the bulk photovoltaic effect (BPE). The recent successful application of inorganic and hybrid perovskite structured materials (e.g. BiFeO3, CsSnI3, CH3NH3PbI3) in solar cells emphasises that polar semiconductors can be used in conventional photovoltaic architectures. We review developments in this field, with a particular emphasis on the materials known to display the APE/BPE (e.g. ZnS, CdTe, SbSI), and the theoretical explanation. Critical analysis is complemented with first-principles calculation of the underlying electronic structure. In addition to discussing the implications of a ferroelectric absorber layer, and the solid state theory of polarisation (Berry phase analysis), design principles and opportunities for high-efficiency ferroelectric photovoltaics are presented

Electronic chemical potentials of porous metal-organic frameworks

The binding energy of an electron in a material is a fundamental characteristic, which determines a wealth of important chemical and physical properties. For metal-organic frameworks this quantity is hitherto unknown. We present a general approach for determining the vacuum level of porous metal-organic frameworks and apply it to obtain the first ionisation energy for six prototype materials including zeolitic, covalent and ionic frameworks. This approach for valence band alignment can explain observations relating to the electrochemical, optical and electrical properties of porous frameworks

Long Live the Dead Hand: A Case for Repeal of the Rule Against Perpetuities in Washington

The common law rule against perpetuities has had a storied career spanning several centuries and two legal systems. The rule developed to curb the concentration of wealth in the hands of a few, and to limit the control of property by those no longer alive to use it. Legendary for its complexity, the rule has undergone statutory reform in many states; some states have gone so fara s to repeal the rule outright. Washington has embraced two of the major reforms of the rule and is considering repeal. This Comment argues that the rule, even with reform, no longer serves the policies for which it was designed. The threats posed by dead hand control are no longer pressing, and extant legal mechanisms are adequate to deal with the threats that remain. Reform is too mild a response to the rule\u27s shortcomings. Washington, therefore, should repeal the rule

I Live in a Place That a River Runs Through: Localized Literacy, Currere and a Summer in an Ojibway Community

In this paper, I analyze a particular artifact from my lived curriculum – a short children’s book I wrote while running a literacy program in an Ojibway community. In doing this, I draw upon Ng-A-Fook’s (2011) (re)imagining of currere as specific experiential snapshots that open up into wider landscapes of meaning. After situating the book within my own lived experience, I unlock some of the meanings contained in it by analyzing it through three different theoretical lenses. I first examine the book in relation to research on place-based literacy (e.g. Kulnieks, Longboat, & Young, 2010), and suggest the value of such a localized approach to literacy education. Secondly, in relation to the scholarship on settler colonialism (e.g. Tuck & Gaztambide-Fernández, 2013), I question whether my choice as an outsider to write a work of “literature” incorporating aspects of local intergenerational knowledges should be seen an act of appropriation. Thirdly, I draw on literature arguing for the development of ethical intercultural meeting places (e.g. Haig-Brown, 2008) in order to suggest that this artifact is best understood as a record of my gradual development as an educator and a researcher. I suggest that currere is not just a way for teachers to become “amateur intellectuals” (Kanu & Glor, 2006), but also a way for researchers like such as myself to become “amateur practitioners,” by learning to situate our experience within the skilled practices of a curriculum of place (Chambers, 2008)

Non-LTE line-formation for CNO

Accurate atomic data have become available in the recent past due to the demands of astrophysics and fusion research. We report on the impact of such data on non-LTE line-formation calculations for CNO in early-type stars. Considerable improvement is achieved by the derivation of consistent results from practically all available spectroscopic indicators, regardless of ionization stage or spin system, and the uncertainties in the analyses are drastically reduced. Moreover, systematic trends are revealed, e.g. an increase of the NI abundances from previous studies of BA-type supergiants by a factor of two is indicated. The present work promises stringent observational constraints on chemical mixing in the course of massive star evolution. First results on BA-type supergiants in the Galaxy and the Magellanic Clouds are discussed.Comment: 6 pages, 2 figures; to be published in "CNO in the Universe", ASP Conf. Series, eds. C. Charbonnel, D. Schaerer & G. Meyne

Getting into sheep an introductory guide to sheep management

Sheep husbandry can be an interesting and rewarding activity but before starting to work with or buy sheep ask yourself if you are prepared to spend the time and effort to care for them. Sheep cannot be placed in a paddock and forgotten. The sheep, along with their water, feed and fences must be inspected regularly. If you do not live on the farm, or visit it only infrequently, make sure there is a responsible person available who is willing to inspect and manage the sheep on your behalf.https://researchlibrary.agric.wa.gov.au/bulletins/1201/thumbnail.jp