Power filters for gravitational wave bursts: network operation for source position estimation

A method is presented to generalize the power detectors for short bursts of gravitational waves that have been developed for single interferometers so that they can optimally process data from a network of interferometers. The performances of this method for the estimation of the position of the source are studied using numerical simulations.Comment: To appear in the proceedings of GWDAW 2002 (Classical and Quantum Gravity, Special issue

History of advertising by accountants

The accounting profession has changed to meet the requirements of business, government and other economic influences. In particular, standards of practice and principles to guide the selection of choices have been developed, modified, restated and fine-tuned over the past 70 to 80 years in response to the needs of an expanding American economy. Accountants wanted to be a profession, and advertising was believed to be unethical. This belief has also changed, and accountants have come full circle in the matter of advertising

A new practical and economical technique for the obtention of high quality thin section photographs with the help of a simple optical microscope

Microscopic study is an indispensable step in the determination of the petrographic characteristics of rocks. In Cameroon just like in most developing countries, simple polarizing microscopes of the 20th Century constitute the only available material for macroscopic studies. A major difficulty encountered in the use of these instruments resides in the realisation of photographs of the different parts of the thin section that require illustrations. The technique that has been used upto now has been inefficient and unsatisfactory. Faced with this recurrent situation, we thought of setting up a new, semi-modern, practical and very economical technique for photographing the thin section.conferenc

Water Quality at the Inlet to the St. Lawrence River, 1977 to 1983

Daily nutrients analyses and weekly major ions and trace metals analyses have been performed since 1977 on water samples collected in the south channel of the St. Lawrence River at Wolfe Island. This report presents the results of the first seven years of this program. Data analyses showed that pH and total phosphorus were underestimated. Calcium carbonate precipitation is suspected to occur almost every year in August or September. Most of the major ions have decreased, especially chloride and sodium. All trace metal data were below the objectives of the International Joint Commission in 90% of the cases or more. The Wolfe Island station was found to be a good tool for following the general trend of the main water quality parameters. More attention, however, should be focused on the problems of shipping delays and containers

Search for cool giant exoplanets around young and nearby stars - VLT/NaCo near-infrared phase-coronagraphic and differential imaging

[Abridged] Context. Spectral differential imaging (SDI) is part of the observing strategy of current and future high-contrast imaging instruments. It aims to reduce the stellar speckles that prevent the detection of cool planets by using in/out methane-band images. It attenuates the signature of off-axis companions to the star, such as angular differential imaging (ADI). However, this attenuation depends on the spectral properties of the low-mass companions we are searching for. The implications of this particularity on estimating the detection limits have been poorly explored so far. Aims. We perform an imaging survey to search for cool (Teff<1000-1300 K) giant planets at separations as close as 5-10 AU. We also aim to assess the sensitivity limits in SDI data taking the photometric bias into account. This will lead to a better view of the SDI performance. Methods. We observed a selected sample of 16 stars (age < 200 Myr, d < 25 pc) with the phase-mask coronagraph, SDI, and ADI modes of VLT/NaCo. Results. We do not detect any companions. As for the sensitivity limits, we argue that the SDI residual noise cannot be converted into mass limits because it represents a differential flux, unlike the case of single-band images. This results in degeneracies for the mass limits, which may be removed with the use of single-band constraints. We instead employ a method of directly determining the mass limits. The survey is sensitive to cool giant planets beyond 10 AU for 65% and 30 AU for 100% of the sample. Conclusions. For close-in separations, the optimal regime for SDI corresponds to SDI flux ratios >2. According to the BT-Settl model, this translates into Teff<800 K. The methods described here can be applied to the data interpretation of SPHERE. We expect better performance with the dual-band imager IRDIS, thanks to more suitable filter characteristics and better image quality.Comment: 19 pages, 16 figures, accepted for publication in A&A, version including language editin

Search for cool extrasolar giant planets combining coronagraphy, spectral and angular differential imaging

Spectral differential imaging (SDI) is part of the observing strategy of current and on-going high-contrast imaging instruments on ground-based telescopes. Although it improves the star light rejection, SDI attenuates the signature of off-axis companions to the star, just like angular differential imaging (ADI). However, the attenuation due to SDI has the peculiarity of being dependent on the spectral properties of the companions. To date, no study has investigated these effects. Our team is addressing this problem based on data from a direct imaging survey of 16 stars combining the phase-mask coronagraph, the SDI and the ADI modes of VLT/NaCo. The objective of the survey is to search for cool (Teff<1000-1300 K) giant planets at separations of 5-10 AU orbiting young, nearby stars (<200 Myr, <25 pc). The data analysis did not yield any detections. As for the estimation of the sensitivity limits of SDI-processed images, we show that it requires a different analysis than that used in ADI-based surveys. Based on a method using the flux predictions of evolutionary models and avoiding the estimation of contrast, we determine directly the mass sensitivity limits of the survey for the ADI processing alone and with the combination of SDI and ADI. We show that SDI does not systematically improve the sensitivity due to the spectral properties and self-subtraction of point sources.Comment: 5 pages, 2 figure

The oxygen isotopic composition of phytolith assemblages from tropical rainforest soil tops (Queensland, Australia): validation of a new paleoenvironmental tool

Phytoliths are micrometric particles of amorphous silica that form inside or between the cells of higher plant tissues throughout the life of a plant. With plant decay, phytoliths are either incorporated into soils or exported to sediments via regional watersheds. Phytolith morphological assemblages are increasingly used as proxy of grassland diversity and tree cover density in inter-tropical areas. Here, we investigate whether, along altitudinal gradients in northeast Queensland (Australia), changes in the &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O signature of soil top phytolith assemblages reflect changes in mean annual temperature (MAT) and in the oxygen isotopic composition of precipitation (&amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;precipitation&lt;/sub&gt;), as predicted by equilibrium temperature coefficients previously published for silica. Oxygen isotopic analyses were performed on 16 phytolith samples, after controlled isotopic exchange (CIE), using the IR Laser-Heating Fluorination Technique. Long-term mean annual precipitation (MAP) and MAT values at the sampled sites were calculated by the ANUCLIM software. &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;precipitation&lt;/sub&gt; estimates were calculated using the Bowen and Wilkinson (2002) model, slightly modified. An empirical temperature-dependant relationship was obtained: &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;wood phytolith-precipitation&lt;/sub&gt; (&amp;permil; vs. VSMOW) = −0.4 (±0.2) &lt;i&gt;t&lt;/i&gt; (°C) + 46 (±3) (&lt;i&gt;R&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt; = 0.4, &lt;i&gt;p&lt;/i&gt; &lt; 0.05; &lt;i&gt;n&lt;/i&gt; = 12). Despite the various unknowns introduced when estimating &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;precipitation&lt;/sub&gt; values and the large uncertainties on &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;wood phytolith&lt;/sub&gt; values, the temperature coefficient (−0.4 ± 0.2&amp;permil; °C&lt;sup&gt;−1&lt;/sup&gt;) is in the range of values previously obtained for natural quartz, fresh and sedimentary diatoms and harvested grass phytoliths (from −0.2 to −0.5&amp;permil; °C&lt;sup&gt;−1&lt;/sup&gt;). The consistency supports the reliability of &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;wood phytolith&lt;/sub&gt; signatures for recording relative changes in mean annual &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;soil water&lt;/sub&gt; values (which are assumed to be equivalent to the weighted annual &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt; precipitation&lt;/sub&gt; values in rainforests environments) and MAT, provided these changes were several &amp;permil; and/or several °C in magnitude