A High Resolution Intergalactic Explorer for the Soft X-ray/FUV

We present a mission concept for high resolution X-ray spectroscopy with a resolving power, R~6000, (c.f. R=<1000 for Chandra, XMM-Newton). This resolution is physics-driven, since it allows the thermal widths of coronal X-ray lines to be measured, and astrophysics-driven, since 50 km/s resolves internal galaxy motions, and galaxy motions within larger structures. Such a mission could be small and have a rapid response allowing us to `X-ray the Universe' using the afterglows of Gamma-ray Bursts (GRBs) as strong background sources of X-rays, and so illuminate the `Cosmic Web'. The Cosmic Web is predicted to contain most of the normal matter (baryons) in the nearby Universe.Comment: Paper presented at the August 2002 SPIE meeting "Astronomical Telescopes and Instrumentation", Kona, Hawai

Accessible Spectrum Analyser

Presented at the 22nd International Conference on Auditory Display (ICAD-2016)This paper presents the Accessible Spectrum Analyser (ASA) developed as part of the DePic project (Design Patterns for Inclusive collaboration) at Queen Mary University of London. The ASA uses sonification to provide an accessible representation of frequency spectra to visually impaired audio engineers. The software is free and open source and is distributed as a VST plug-in under OSX and Windows. The aim of reporting this work at the ICAD 2016 conference is to solicit feedback about the design of the present tool and its more generalized counterpart, as well as to invite ideas for other possible applications where it is thought that auditory spectral analysis may be useful, for example in situations where line of sight is not always possible

Can one improve the Froissart bound?

We explain why we hope that the Froissart bound can be improved, either qualitatively or, more likely, quantitatively, by making a better use of unitarity, in particular elastic unitarity. In other instances (Gribov's theorem) elastic unitarity played a crucial role. A preliminary requirement for this is to work with an appropriate average of the cross-section, to make the problem well defined. This is possible, without destroying the Lukaszuk--Martin bound.Comment: 4 pages, latex with AIP style, Talk given at "Diffraction 2008", Lalonde-les-Maures, France, September 2008. Missing square root restored p. 3. pi^2->pi corrected in eq. (1

Initial Semantics for Strengthened Signatures

We give a new general definition of arity, yielding the companion notions of signature and associated syntax. This setting is modular in the sense requested by Ghani and Uustalu: merging two extensions of syntax corresponds to building an amalgamated sum. These signatures are too general in the sense that we are not able to prove the existence of an associated syntax in this general context. So we have to select arities and signatures for which there exists the desired initial monad. For this, we follow a track opened by Matthes and Uustalu: we introduce a notion of strengthened arity and prove that the corresponding signatures have initial semantics (i.e. associated syntax). Our strengthened arities admit colimits, which allows the treatment of the \lambda-calculus with explicit substitution.Comment: In Proceedings FICS 2012, arXiv:1202.317

Mapping isoprene emissions over North America using formaldehyde column observations from space

We present a methodology for deriving emissions of volatile organic compounds (VOC) using space-based column observations of formaldehyde (HCHO) and apply it to data from the Global Ozone Monitoring Experiment (GOME) satellite instrument over North America during July 1996. The HCHO column is related to local VOC emissions, with a spatial smearing that increases with the VOC lifetime. Isoprene is the dominant HCHO precursor over North America in summer, and its lifetime (≃1 hour) is sufficiently short that the smearing can be neglected. We use the Goddard Earth Observing System global 3-D model of tropospheric chemistry (GEOS-CHEM) to derive the relationship between isoprene emissions and HCHO columns over North America and use these relationships to convert the GOME HCHO columns to isoprene emissions. We also use the GEOS-CHEM model as an intermediary to validate the GOME HCHO column measurements by comparison with in situ observations. The GEOS-CHEM model including the Global Emissions Inventory Activity (GEIA) isoprene emission inventory provides a good simulation of both the GOME data (r2 = 0.69, n = 756, bias = +11%) and the in situ summertime HCHO measurements over North America (r2 = 0.47, n = 10, bias = −3%). The GOME observations show high values over regions of known high isoprene emissions and a day-to-day variability that is consistent with the temperature dependence of isoprene emission. Isoprene emissions inferred from the GOME data are 20% less than GEIA on average over North America and twice those from the U.S. EPA Biogenic Emissions Inventory System (BEIS2) inventory. The GOME isoprene inventory when implemented in the GEOS-CHEM model provides a better simulation of the HCHO in situ measurements than either GEIA or BEIS2 (r2 = 0.71, n = 10, bias = −10%)

The Equilibrium Photoionized Absorber in 3C351

We present two ROSAT PSPC observations of the radio-loud, lobe-dominated quasar 3C 351, which shows an `ionized absorber' in its X-ray spectrum. The factor 1.7 change in flux in the $\sim$2~years between the observations allows a test of models for this ionized absorber. The absorption feature at ~0.7 keV (quasar frame) is present in both spectra but with a lower optical depth when the source intensity - and hence the ionizing flux at the absorber - is higher, in accordance with a simple, single-zone, equilibrium photoionization model. Detailed modeling confirms this agrement quantitatively. The maximum response time of 2 years allows us to limit the gas density: n_e > 2 x 10^4 cm^{-3}; and the distance of the ionized gas from the central source R < 19 pc. This produces a strong test for a photoionized absorber in 3C~351: a factor 2 flux change in ~1 week in this source must show non-equilibrium effects in the ionized absorber.Comment: 10 pages, 3 figures, accepted by Ap