Comment on "Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics"

The incorporation of systematic uncertainties into confidence interval calculations has been addressed recently in a paper by Conrad et al. (Physical Review D 67 (2003) 012002). In their work, systematic uncertainities in detector efficiencies and background flux predictions were incorporated following the hybrid frequentist-Bayesian prescription of Cousins and Highland, but using the likelihood ratio ordering of Feldman and Cousins in order to produce "unified" confidence intervals. In general, the resulting intervals behaved as one would intuitively expect, i.e. increased with increasing uncertainties. However, it was noted that for numbers of observed events less than or of order of the expected background, the intervals could sometimes behave in a completely counter-intuitive fashion -- being seen to initially decrease in the face of increasing uncertainties, but only for the case of increasing signal efficiency uncertainty. In this comment, we show that the problematic behaviour is due to integration over the signal efficiency uncertainty while maximising the best fit alternative hypothesis likelihood. If the alternative hypothesis likelihood is determined by unconditionally maximising with respect to both the unknown signal and signal efficiency uncertainty, the limits display the correct intuitive behaviour.Comment: Submitted to Physical Review

No Exit Plan From This Altitude

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Treatment of the background error in the statistical analysis of Poisson processes

The formalism that allows to take into account the error sigma_b of the expected mean background b in the statistical analysis of a Poisson process with the frequentistic method is presented. It is shown that the error sigma_b cannot be neglected if it is not much smaller than sqrt(b). The resulting confidence belt is larger that the one for sigma_b=0, leading to larger confidence intervals for the mean mu of signal events.Comment: 15 pages including 2 figures, RevTeX. Final version published in Phys. Rev. D 59 (1999) 11300

Use of magnetic and olfactory cues for orientation by a fossorial rodent, Thomomys talpoides

Fossorial, or below ground, living provides shelter from the elements and some predators, but comes at a cost with respect to metabolic requirements of movement and reduced, or altered, sensory cues. I examined the ability of the North American pocket gopher, Thomomys talpoides, to use magnetoreception and olfaction in navigation and foraging. Magnetoreception was tested using three manipulative experiments: 1) field homing of displaced animals, 2) nest location in an 8-arm maze, and 3) movement through a complex labyrinth. Homing results, analyzed by V-test, indicated that the gophers displaced from their burrow systems relied on magnetic cues for homing orientation. Although Rayleigh analysis of the 8-arm maze tests showed limited significance, gophers tended to nest in the conditioned direction, and nesting direction shifted with an altered field. Repeated Measures ANOVA results of performance in time and number of wrong turns in the complex labyrinth showed no significant differences between conditioned trials (unaltered-field) and test (field rotated 90°) trials. Use of olfaction was tested in T-maze trials with soils containing carrot kairomone versus control soil. Binomial probability analysis revealed in all tests comparing carrot soil vs. control that gophers disproportionally selected the carrot soils. Overall my study suggests T talpoides can use both magnetic and olfactory cues while navigating, but the use of these cues is situation dependent. These results are similar to those found in other South American and Old World fossorial rodents --Document

Low-level seaweed supplementation improves iodine status in iodine-insufficient women

Iodine insufficiency is now a prominent issue in the UK and other European countries due to low intakes of dairy products and seafood (especially where iodine fortification is not in place). In the present study, we tested a commercially available encapsulated edible seaweed (Napiers Hebridean Seagreens® Ascophyllum nodosumspecies) for its acceptability to consumers and iodine bioavailability and investigated the impact of a 2-week daily seaweed supplementation on iodine concentrations and thyroid function. Healthy non-pregnant women of childbearing age, self-reporting low dairy product and seafood consumption, with no history of thyroid or gastrointestinal disease were recruited. Seaweed iodine (712 μg, in 1 g seaweed) was modestly bioavailable at 33 (interquartile range (IQR) 28–46) % of the ingested iodine dose compared with 59 (IQR 46–74) % of iodine from the KI supplement (n 22). After supplement ingestion (2 weeks, 0•5 g seaweed daily, <i>n</i> 42), urinary iodine excretion increased from 78 (IQR 39–114) to 140 (IQR 103–195) μg/l (<i>P</i>< 0•001). The concentrations of thyroid-stimulating hormone increased from 1•5 (IQR 1•2–2•2) to 2•1 (IQR 1•3–2•9) mIU/l (<i>P</i>< 0•001), with two participants having concentrations exceeding the normal range after supplement ingestion (but normal free thyroxine concentrations). There was no change in the concentrations of other thyroid hormones after supplement ingestion. The seaweed was palatable and acceptable to consumers as a whole food or as a food ingredient and effective as a source of iodine in an iodine-insufficient population. In conclusion, seaweed inclusion in staple foods would serve as an alternative to fortification of salt or other foods with KI

Spectrophotometry of nearby field galaxies: the data

We have obtained integrated and nuclear spectra, as well as U, B, R surface photometry, for a representative sample of 196 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (M_B=-14 to -22). Here we present the spectrophotometry for these galaxies. The selection of the sample and the U, B, R surface photometry is described in a companion paper (Paper I). Our goals for the project include measuring the current star formation rates and metallicities of these galaxies, and elucidating their star formation histories, as a function of luminosity and morphology. We thereby extend the work of Kennicutt (1992a) to lower luminosity systems. We anticipate that our study will be useful as a benchmark for studies of galaxies at high redshift. We describe the observing, data reduction and calibration techniques, and demonstrate that our spectrophotometry agrees well with that of Kennicutt. The spectra span the range 3550--7250 A at a resolution (FWHM) of ~6 A, and have an overall relative spectrophotometric accuracy of +/- 6 per cent. We present a spectrophotometric atlas of integrated and nuclear rest-frame spectra, as well as tables of equivalent widths and synthetic colors. We study the correlations of galaxy properties determined from the spectra and images. Our findings include: (1) galaxies of a given morphological class display a wide range of continuum shapes and emission line strengths if a broad range of luminosities are considered, (2) emission line strengths tend to in- crease and continua tend to get bluer as the luminosity decreases, and (3) the scatter on the general correlation between nuclear and integrated H_alpha emission line strengths is large.Comment: Accepted for publication in ApJS (scheduled for Vol.127, 2000 March); 63 pages, LateX, 9 figures and 6 tables included, a spectrophotometric atlas is provided as GIF images, fig 1 as a JPEG image, in a single tar-file; a full 600 dpi version is available at http://www.astro.rug.nl/~nfgs