The Status of the H.E.S.S. Project

The High Energy Stereoscopic System (H.E.S.S.) - is a system of four, 107 m^2 mirror area, imaging Cherenkov telescopes under construction in the Khomas Highland of Namibia (1800 m asl). The H.E.S.S. system is characterised by a low threshold (~ 100 GeV) and a ~1 % Crab flux sensitivity resulting from the good angular resolution and background rejection provided by the stereoscopic technique. The first two telescopes are operational and first results are reported here. The remaining two telescopes (of H.E.S.S. Phase-I) will be commissioned early in 2004.Comment: 8 pages, 16 figures, in 2nd VERITAS Symposium on TeV Astrophysics (eds. L. Fortson and S. Swordy), New Astronomy Reviews (in press

A Monte Carlo Template based analysis for Air-Cherenkov Arrays

We present a high-performance event reconstruction algorithm: an Image Pixel-wise fit for Atmospheric Cherenkov Telescopes (ImPACT). The reconstruction algorithm is based around the likelihood fitting of camera pixel amplitudes to an expected image template. A maximum likelihood fit is performed to find the best-fit shower parameters. A related reconstruction algorithm has already been shown to provide significant improvements over traditional reconstruction for both the CAT and H.E.S.S. experiments. We demonstrate a significant improvement to the template generation step of the procedure, by the use of a full Monte Carlo air shower simulation in combination with a ray-tracing optics simulation to more accurately model the expected camera images. This reconstruction step is combined with an MVA-based background rejection. Examples are shown of the performance of the ImPACT analysis on both simulated and measured (from a strong VHE source) gamma-ray data from the H.E.S.S. array, demonstrating an improvement in sensitivity of more than a factor two in observation time over traditional image moments-fitting methods, with comparable performance to previous likelihood fitting analyses. ImPACT is a particularly promising approach for future large arrays such as the Cherenkov Telescope Array (CTA) due to its improved high-energy performance and suitability for arrays of mixed telescope types.Comment: 13 pages, 10 figure

Mating Frequency of European Corn Borer (Lepidoptera: Crambidae) in Minnesota, Kansas, and Texas

The frequency of mating and polyandry in natural populations are important parameters for understanding evolutionary dynamics. Mating frequency among natural populations of Ostrinia nubilalis (Hübner) [Lepidoptera: Crambidae] are quite variable. Showers et al. (1974) found 91.1, 73.8, and 71.3% of females had mated during the second flight over 1971-3 at one location in Iowa. During 1971, only 10% mated multiple times, with lower levels of polyandry in subsequent years. In an earlier study in Iowa, Pesho (1961) found that 65-100 % of females had mated and up to 43% had mated more than once. A population in southwestern Ontario averaged 73% mating and 37% polyandry for the 5-year period from 1971-5, a higher rate of polyandry than during the same period in Iowa (Elliot, 1977). In this note, we amplify these previously published results by reporting the mating status of female O. nubilalis captured in light traps in Minnesota, Kansas and Texas. We also provide evidence that some females in natural populations may be sperm-limited

The experimental determination of tyre model parameters

SUMMARY This report describes the analysis of a series of experiments on pneumatic tyres which were designed to test the various hypotheses: regarding the deformed shape of a tyre during the steering process. The experiments consisted of several separate tests first described in Ref. 1 and 2. a) The application of a point lateral force or a moment at one position on the tread band which is restrained at the centre of the wheel, and the measurement of the resulting lateral deflection of each point of the tyre perimeter. b) The application of a uniform force around the tyre perimeter on a hollow cylindrical former and applying a load at the centre of the wheel. c) Direct determination of tread band tension by cutting the tread band and bridging the cut by a dynamometer. d) Estimation of the bending modulus of the tread band by test on sections cut from the tread band. The analysis of the experiments is carried out by first transforming the test results into a Fourier series and determining the spectral content of the bending line with an harmonic analysis. Transfer functions of beam and string models are derived and applied to the test results. A method of considering a three parameter model is described

The Measure of Meetings: Forums, Deliberation, and Cultural Policy

This research seeks to answer the question: “Do meetings matter for advancing cultural policy?” The question is approached theoretically and comparatively by examining the broader literature on policy making, as well specific case studies of meetings in other fields, in order to draw lessons and implications for arts and culture; discursively and ethnographically, by attending the annual meetings of arts service associations and recording and interpreting how people at these meetings talked about problems and policy; and empirically, by looking at a sample of conference program books over ten years and coding and analyzing what issues were discussed and who was invited to discuss them. We also studied, in detail, what a random sample of 40 participants say they learned at a particular annual convention and what policy-relevant actions they took as a result of having attended the meeting. Overall, we find that meetings are not currently effective tools for advancing policy in the cultural sector, with some notable exceptions. In arts and culture, where resources are modest, where the policy community is fragmented, where problems are poorly defined, where there is no central authority or government agency, and where issues have low salience for the general public, welltimed and carefully orchestrated meetings can perhaps play an even more important role than they do in other fields.

Energy-based temporal neural networks for imputing missing values

Imputing missing values in high dimensional time series is a difficult problem. There have been some approaches to the problem [11,8] where neural architectures were trained as probabilistic models of the data. However, we argue that this approach is not optimal. We propose to view temporal neural networks with latent variables as energy-based models and train them for missing value recovery directly. In this paper we introduce two energy-based models. The first model is based on a one dimensional convolution and the second model utilizes a recurrent neural network. We demonstrate how ideas from the energy-based learning framework can be used to train these models to recover missing values. The models are evaluated on a motion capture dataset

Perturbations to observed ambient neutral densities due to presence of an Orbiting Geophysical Observatory

Perturbations in density of ions and neutral particles in upper atmosphere due to OG

HESS J1825-137: A pulsar wind nebula associated with PSR B1823-13?

HESS J1825-137 was detected with a significance of 8.1 $\sigma$ in the Galactic Plane survey conducted with the H.E.S.S. instrument in 2004. Both HESS J1825-137 and the X-ray pulsar wind nebula G18.0--0.7 (associated with the Vela-like pulsar PSR B1823-13) are offset south of the pulsar, which may be the result of the SNR expanding into an inhomogeneous medium. The TeV size ($\sim 35$ pc, for a distance of 4 kpc) is $\sim 6$ times larger than the X-ray size, which may be the result of propagation effects as a result of the longer lifetime of TeV emitting electrons, compared to the relatively short lifetime of keV synchrotron emitting electrons. The TeV photon spectral index of $\sim 2.4$ can also be related to the extended PWN X-ray synchrotron photon index of $\sim 2.3$, if this spectrum is dominated by synchrotron cooling. The anomalously large size of the pulsar wind nebula can be explained if the pulsar was born with a relatively large initial spindown power and braking index $n\sim 2$, provided that the SNR expanded into the hot ISM with relatively low density ($\sim 0.003$ cm$^{-3}$).Comment: 4 pages, 4 figures, to appear in the Proc. of the 29th International Cosmic Ray Conference, OG Sessio