Seeking a solution of the Pioneer Anomaly

The 1972 and 1973 launched Pioneer 10 and 11 were the first missions to explore the outer solar system. They achieved stunning breakthroughs in deep-space exploration. But around 1980 an unmodeled force of \sim 8 \times 10^{-8} cm/s^2, directed approximately towards the Sun, appeared in the tracking data. It later was unambiguously verified as not being an artifact. The origin remains unknown (although radiant heat remains a likely cause). Increasing effort has gone into understanding this anomaly. We review the situation and describe programs to resolve the issue.Comment: 7 pages, 1 figure, invited talk at the Fourth Meeting on CPT and Lorentz Symmetry, 8-11 Aug. 2007, held at Indiana Universit

Earth Flyby Anomalies

In a reference frame fixed to the solar system's center of mass, a satellite's energy will change as it is deflected by a planet. But a number of satellites flying by Earth have also experienced energy changes in the Earth-centered frame -- and that's a mystery.Comment: 5 pagea 3 figure

High-dimensional Ising model selection using ℓ1{\ell_1}-regularized logistic regression

We consider the problem of estimating the graph associated with a binary Ising Markov random field. We describe a method based on $\ell_1$-regularized logistic regression, in which the neighborhood of any given node is estimated by performing logistic regression subject to an $\ell_1$-constraint. The method is analyzed under high-dimensional scaling in which both the number of nodes $p$ and maximum neighborhood size $d$ are allowed to grow as a function of the number of observations $n$. Our main results provide sufficient conditions on the triple $(n,p,d)$ and the model parameters for the method to succeed in consistently estimating the neighborhood of every node in the graph simultaneously. With coherence conditions imposed on the population Fisher information matrix, we prove that consistent neighborhood selection can be obtained for sample sizes $n=\Omega(d^3\log p)$ with exponentially decaying error. When these same conditions are imposed directly on the sample matrices, we show that a reduced sample size of $n=\Omega(d^2\log p)$ suffices for the method to estimate neighborhoods consistently. Although this paper focuses on the binary graphical models, we indicate how a generalization of the method of the paper would apply to general discrete Markov random fields.Comment: Published in at http://dx.doi.org/10.1214/09-AOS691 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

An Assessment of the Economic, Environmental and Social Impacts of NSW Agriculture's Wheat Breeding Program

The Wagga wheat breeding program has been operating for over 100 years. In that time, it has released a flow of new wheat varieties for wheat growers in south-eastern Australia. Those varieties have led to increases in both yields and grain quality. The average annual rate of yield improvement in NSW has been 3.2% compared to the average for Australia of 2.4% with a significant proportion of these productivity gains arising from new varieties. In this analysis, the investment in that program from 1980 to 2003 has been evaluated. Given the lags inherent in wheat breeding investments, the benefits from those investments are being measured from 1993 to 2020. The broad structure of the program has remained relatively stable for most of the period since 1980. The program consists of 2-3 wheat breeders, one breeder-pathologist, and a cereal chemist, with appropriate technical and field support, totaling approximately 15 full-time equivalents per year. The costs of the program have averaged approximately $1.2 million per year over the period. In assessing the Wagga wheat breeding program it is important to consider how the industry would have developed without the program. The benefits of the program were measured as the difference in returns from improved wheat varieties in NSW over that period and the returns that would have been achieved in the absence of the Wagga breeding program. The assumption used to determine the impact without the Wagga program was that the rate of yield improvement in NSW would have been the same as for the rest of Australia. For quality, without the Wagga program the assumption was that in southern NSW the increase in quality would have been 20$321 million. The economic benefits of the breeding program are shared by producers, processors and consumers in the wheat industry, some of whom live overseas. Because Australia is largely a price taker on world wheat markets and because the wheat processing and distribution sector in Australia is generally considered to be competitive, most of the benefits of the wheat breeding program are likely to remain with producers. However these gains are offset by declines in the world price in response to advancing technology throughout the world. These economic benefits have positive social consequences, largely through their contribution to the incomes of farmers and those who handle and process wheat in regional NSW. Some of these gains are in the form of new marketing and processing industries around the increasingly specialised industry segments resulting directly from the changes that have occurred in wheat varieties. Perhaps these new skills add to the social capital of towns in the wheat belt of NSW. In environmental terms, the wheat breeding program itself is not likely to have major impacts, since the wheat industry would have been very similar whether or not there was a Wagga breeding program. However, to the extent that improved productivity from the Wagga program's varieties has allowed an expansion of the wheat industry, there could be some negative environmental consequences of the breeding program, such as those arising from the clearing of land, increased cultivation and increased use of herbicides. On the other hand, the high levels of disease resistance developed and maintained has meant that wheat production is not associated with large-scale fungicide use, and hence the danger of chemical contamination of the environment is less than it would have been without the resistance developed in this program. Some of these environmental impacts affect the costs and incomes of wheat farmers and hence are reflected in economic benefits and some spill over to the broader community and have not been valued here. It is not clear that these social and environmental impacts would be much different without the Wagga breeding program, except through the extent to which the Wagga program has allowed the wheat industry in NSW to develop more than it otherwise would have. Without the Wagga program the slower gains in yield and quality would also be associated with some social and environmental impacts, and it is the difference that is critical in evaluating the Wagga program. The costs of this program have been met partly by the NSW taxpayers through NSW Agriculture and partly by the grains industry through levies from the Grains Research and Development Corporation (GRDC). The recent introduction of variety royalty payments ("end-point royalties") has not yet led to significant funding, but may be expected to do so in the future. The nature of the outputs of plant breeding programs is that there are large economic benefits that flow directly to producers, processors and consumers in the industry. However the social and environmental impacts on the broader community, while not explicitly valued here, are considered to be small relative to economic benefits and relative to some other programs of NSW Agriculture that have been evaluated. Hence it is appropriate that the industry, though GRDC levies and royalties on production, has increasingly funded the operations of the wheat breeding program. Recent institutional changes for the wheat breeding program have made it even more commercially-based for the future and less reliant on government funding. The new institutional arrangements for wheat breeding programs and the strengthening role of the private sector in supplying varieties traditionally supplied by the public sector mean that the place of public wheat breeding programs is being re-assessed. A key question is whether publicly-operated programs, can offer some additional benefits either to the industry or to the community, which would not result from the complete privatisation of the wheat breeding sector. While those issues have not been addressed directly in this analysis, the results indicate that past investments in public wheat breeding program at Wagga have certainly been a productive use of public funds over the past 20 years or so.Research and Development/Tech Change/Emerging Technologies,

Distributions associated with general runs and patterns in hidden Markov models

This paper gives a method for computing distributions associated with patterns in the state sequence of a hidden Markov model, conditional on observing all or part of the observation sequence. Probabilities are computed for very general classes of patterns (competing patterns and generalized later patterns), and thus, the theory includes as special cases results for a large class of problems that have wide application. The unobserved state sequence is assumed to be Markovian with a general order of dependence. An auxiliary Markov chain is associated with the state sequence and is used to simplify the computations. Two examples are given to illustrate the use of the methodology. Whereas the first application is more to illustrate the basic steps in applying the theory, the second is a more detailed application to DNA sequences, and shows that the methods can be adapted to include restrictions related to biological knowledge.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS125 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

The Pioneer Anomaly and Its Implications

The Pioneer 10/11 spacecraft yielded the most precise navigation in deep space to date. However, their radio-metric tracking data has consistently indicated the presence of a small, anomalous, Doppler frequency drift. The drift is a blue-shift, uniformly changing with a rate of ~6 x 10^{-9} Hz/s and can be interpreted as a constant sunward acceleration of each particular spacecraft of a_P =(8.74 +/- 1.33) x 10^{-10} m/s^2. The nature of this anomaly remains unexplained. Here we summarize our current knowledge of the discovered effect and review some of the mechanisms proposed for its explanation. Currently we are preparing for the analysis of the entire set of the available Pioneer 10/11 Doppler data which may shed a new light on the origin of the anomaly. We present a preliminary assessment of such an intriguing possibility.Comment: 7 pages, 2 figures. Invited talk given at the XXIst IAP Colloquium on "Mass Profiles and Shapes of Cosmological Structures", Paris, France, July 4-9, 200

Routine characterization and interpretation of complex alkali feldspar intergrowths

Almost all alkali feldspar crystals contain a rich inventory of exsolution, twin, and domain microtextures that form subsequent to crystal growth and provide a record of the thermal history of the crystal and often of its involvement in replacement reactions, sometimes multiple. Microtextures strongly influence the subsequent behavior of feldspars at low temperatures during diagenesis and weathering. They are central to the retention or exchange of trace elements and of radiogenic and stable isotopes. This review is aimed at petrologists and geochemists who wish to use alkali feldspar microtextures to solve geological problems or who need to understand how microtextures influence a particular process. We suggest a systematic approach that employs methods available in most well founded laboratories. The crystallographic relationships of complex feldspar intergrowths were established by the 1970s, mainly using single-crystal X-ray diffraction, but such methods give limited information on the spatial relationships of the different elements of the microtexture, or of the mode and chronology of their formation, which require the use of microscopy. We suggest a combination of techniques with a range of spatial resolution and strongly recommend the use of orientated sections. Sections cut parallel to the perfect (001) and (010) cleavages are the easiest to locate and most informative. Techniques described are light microscopy; scanning electron microscopy using both backscattered and secondary electrons, including the use of surfaces etched in the laboratory; electron-probe microanalysis and analysis by energy-dispersive spectrometry in a scanning electron microscope; transmission electron microscopy. We discuss the use of cathodoluminescence as an auxiliary technique, but do not recommend electron-backscattered diffraction for feldspar work. We review recent publications that provide examples of the need for great care and attention to pre-existing work in microtextural studies, and suggest several topics for future work