Combining local- and large-scale models to predict the distributions of invasive plant species

Habitat-distribution models are increasingly used to predict the potential distributions of invasive species and to inform monitoring. However, these models assume that species are in equilibrium with the environment, which is clearly not true for most invasive species. Although this assumption is frequently acknowledged, solutions have not been adequately addressed. There are several potential methods for improving habitat-distribution models. Models that require only presence data may be more effective for invasive species, but this assumption has rarely been tested. In addition, combining modeling types to form ‘ensemble’ models may improve the accuracy of predictions. However, even with these improvements, models developed for recently invaded areas are greatly influenced by the current distributions of species and thus reflect near- rather than long-term potential for invasion. Larger scale models from species’ native and invaded ranges may better reflect long-term invasion potential, but they lack finer scale resolution. We compared logistic regression (which uses presence/absence data) and two presence-only methods for modeling the potential distributions of three invasive plant species on the Olympic Peninsula in Washington State, USA. We then combined the three methods to create ensemble models. We also developed climate-envelope models for the same species based on larger scale distributions and combined models from multiple scales to create an index of near- and long-term invasion risk to inform monitoring in Olympic National Park (ONP). Neither presence-only nor ensemble models were more accurate than logistic regression for any of the species. Larger scale models predicted much greater areas at risk of invasion. Our index of near- and long-term invasion risk indicates that \u3c4% of ONP is at high near-term risk of invasion while 67-99% of the Park is at moderate or high long-term risk of invasion. We demonstrate how modeling results can be used to guide the design of monitoring protocols and monitoring results can in turn be used to refine models. We propose that by using models from multiple scales to predict invasion risk and by explicitly linking model development to monitoring, it may be possible to overcome some of the limitations of habitat-distribution models

Binary planetary nebulae nuclei towards the Galactic bulge. II. A penchant for bipolarity and low-ionisation structures

Considerable effort has been applied towards understanding the precise shaping mechanisms responsible for the diverse range of morphologies exhibited by planetary nebulae (PNe). A binary companion is increasingly gaining support as a dominant shaping mechanism, however morphological studies of the few PNe that we know for certain were shaped by binary evolution are scarce or biased. Newly discovered binary central stars (CSPN) from the OGLE-III photometric variability survey have significantly increased the sample of post common-envelope (CE) nebulae available for morphological analysis. We present Gemini South narrow-band images for most of the new sample to complement existing data in a qualitative morphological study of 30 post-CE nebulae. Nearly 30% of nebulae have canonical bipolar morphologies, however this rises to 60% once inclination effects are incorporated with the aid of geometric models. This is the strongest observational evidence yet linking CE evolution to bipolar morphologies. A higher than average proportion of the sample shows low-ionisation knots, filaments or jets suggestive of a binary origin. These features are also common around emission-line nuclei which may be explained by speculative binary formation scenarios for H-deficient CSPN.Comment: Accepted for publication in A&

For Joan:Some letters with reverence, an honorary degree, and a dialogical tribute

In 2012, I co‐taught, with Anne‐Charlott Callerstig, a master's course module at Linköping University in Swedenentitled ‘Intersectional Gender, and Institutional and Organizational Work’. Towards the end of the course I was emailed by Donald Van Houten asking for contributions to a text to be presented at a reception on International Women's Day, 8 March 2012, at the University of Oregon, honouring Joan Acker and her remarkable career. The reception was part of the Lorwin Lecture Series on ‘Civil Rights and Civil Liberties’ and the Wayne Morse Center symposium on ‘Gender Equity and Capitalism’. To honour Joan and her legacy, I was asked to send a personal statement testifying to Joan's impact on her life and work, to be collected together in a small book. We were using some of Joan's writing as key texts on the module, so it seemed appropriate to do something collectively, and accordingly I asked the students to write short ‘letters’ to Joan. I sent off our letters, which we called ‘Some Letters Written with Reverence’; I trust Joan received them and liked them. Therefore, here in this writing for Joan there are three parts. In the first, the ‘letters’ are reproduced; the next is the edited proposal I wrote for Joan to be awarded an honorary doctorate at Hanken School of Economics, the Swedish‐language business school in Helsinki, Finland; she received the honour in 2011; and for the last part, I add an additional personal tribute and reflection from the vantage point of now, today

Potassium condensing tests of horizontal multitube convective and radiative condensers operating at vapor temperatures of 1250 deg to 1500 deg F

Potassium condensing tests of horizontal multitube convective and radiative condenser operating at vapor temperature

Spectral analysis of the background in ground-based, long-slit spectroscopy

This paper examines the variations, because of atmospheric extinction, of broad-band visible spectra, obtained from long-slit spectroscopy, in the vicinity of some stars, nebulae, and one faint galaxy.Comment: 12 figure

Power systems research at MSFC

Power systems research reviews at Marshall Space Flight Cente

MSW mediated neutrino decay and the solar neutrino problem

We investigate the solar neutrino problem assuming simultaneous presence of MSW transitions in the sun and neutrino decay on the way from sun to earth. We do a global $\chi^2$-analysis of the data on total rates in Cl, Ga and Superkamiokande (SK) experiments and the SK day-night spectrum data and determine the changes in the allowed region in the \dm - \tan^2\theta plane in presence of decay. We also discuss the implications for unstable neutrinos in the SNO experiment.Comment: Final version to appear in Phys. Rev.

Neutrinoless Double Beta Decay and CP Violation

We study the relation between the Majorana neutrino mass matrices and the neutrinoless double beta decay when CP is not conserved. We give an explicit form of the decay rate in terms of a rephasing invariant quantity and demonstrate that in the presence of CP violation it is impossible to have vanishing neutrinoless double beta decay in the case of two neutrino generations (or when the third generation leptons do not mix with other leptons and hence decouple).Comment: 9 pages, UTPT-93-1