Weyl Expansion for Symmetric Potentials

We present a semiclassical expansion of the smooth part of the density of states in potentials with some form of symmetry. The density of states of each irreducible representation is separately evaluated using the Wigner transforms of the projection operators. For discrete symmetries the expansion yields a formally exact but asymptotic series in $\hbar$, while for the rotational $SO(n)$ symmetries the expansion requires averaging over angular momentum as well as energy. A numerical example is given in two dimensions, in which we calculate the leading terms of the Weyl expansion as well as the leading periodic orbit contributions to the symmetry reduced level density.Comment: Four of the five figures are appended as a postscript file. The fifth figure is available by snail mail

HH 1158: The lowest luminosity externally irradiated Herbig-Haro jet

We have identified a new externally irradiated Herbig-Haro (HH) jet, HH 1158, within ~2 pc of the massive OB type stars in the sigma Orionis cluster. At an Lbol ~ 0.1 Lsun, HH 1158 is the lowest luminosity irradiated HH jet identified to date in any cluster. Results from the analysis of high-resolution optical spectra indicate asymmetries in the brightness, morphology, electron density, velocity, and the mass outflow rates for the blue and red-shifted lobes. We constrain the position angle of the HH 1158 jet at 102+/-5 degree. The mass outflow rate and the mean accretion rate for HH 1158 using multiple diagnostics are estimated to be (5.2 +/- 2.6) x 10^(-10) Msun/yr and (3.0 +/- 1.0) x 10^(-10) Msun/yr, respectively. The properties for HH 1158 are notably similar to the externally irradiated HH 444 -- HH 447 jets previously identified in sigma Orionis. In particular, the morphology is such that the weaker jet beam is tilted towards the massive stars, indicating a higher extent of photo-evaporation. The high value for the Halpha/[SII] ratio is also consistent with the ratios measured in other irradiated jets, including HH 444 -- HH 447. The presence of an extended collimated jet that is bipolar and the evidence of shocked emission knots make HH 1158 the first unique case of irradiated HH jets at the very low-luminosity end, and provides an opportunity to learn the physical properties of very faint HH jet sources.Comment: Accepted in ApJ Letter

Stochastic Gravitational Wave Measurements with Bar Detectors: Dependence of Response on Detector Orientation

The response of a cross-correlation measurement to an isotropic stochastic gravitational-wave background depends on the observing geometry via the overlap reduction function. If one of the detectors being correlated is a resonant bar whose orientation can be changed, the response to stochastic gravitational waves can be modulated. I derive the general form of this modulation as a function of azimuth, both in the zero-frequency limit and at arbitrary frequencies. Comparisons are made between pairs of nearby detectors, such as LIGO Livingston-ALLEGRO, Virgo-AURIGA, Virgo-NAUTILUS, and EXPLORER-AURIGA, with which stochastic cross-correlation measurements are currently being performed, planned, or considered.Comment: 17 pages, REVTeX (uses rcs, amsmath, hyperref, and graphicx style files), 4 figures (8 eps image files

Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217

As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates ($\dot{M}_{out}$/$\dot{M}_{acc}$). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of $\sim$ 20$^{\circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain ($\dot{M}_{out}$/$\dot{M}_{acc}$). The outflow is spatially resolved in the $[SII]\lambda \lambda 6716,6731$ lines and is detected out to $\sim$ 1\farcs6 in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity asymmetry is less pronounced with respect to our previous study. Using thirteen different accretion tracers we measure log($\dot{M}_{acc}$) [M$_{sun}$/yr]= -10.6 $\pm$ 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflow $\dot{M}_{out}$ was derived for a range of values of A$_{v}$, up to a value of A$_{v}$ = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow ($\dot{M}_{out}$) was estimated in the range -11.7 to -11.1 for both jets combined. Thus $\dot{M}_{out}$/$\dot{M}_{acc}$ [\Msun/yr] lies below the maximum value predicted by magneto-centrifugal jet launching models. Finally, both model fitting of the Balmer decrements and spectro-astrometric analysis of the H$\alpha$ line show that the bulk of the H I emission comes from the accretion flow.Comment: accepted by Astronomy & Astrophysic

Inverse meta-modelling to estimate soil available water capacity at high spatial resolution across a farm

Geo-referenced information on crop production that is both spatially- and temporally-dense would be useful for management in precision agriculture (PA). Crop yield monitors provide spatially but not temporally dense information. Crop growth simulation modelling can provide temporal density, but traditionally fail on the spatial issue. The research described was motivated by the challenge of satisfying both the spatial and temporal data needs of PA. The methods presented depart from current crop modelling within PA by introducing meta-modelling in combination with inverse modelling to estimate site-specific soil properties. The soil properties are used to predict spatially- and temporally-dense crop yields. An inverse meta-model was derived from the agricultural production simulator (APSIM) using neural networks to estimate soil available water capacity (AWC) from available yield data. Maps of AWC with a resolution of 10 m were produced across a dryland grain farm in Australia. For certain years and fields, the estimates were useful for yield prediction with APSIM and multiple regression, whereas for others the results were disappointing. The estimates contain ‘implicit information’ about climate interactions with soil, crop and landscape that needs to be identified. Improvement of the meta-model with more AWC scenarios, more years of yield data, inclusion of additional variables and accounting for uncertainty are discussed. We concluded that it is worthwhile to pursue this approach as an efficient way of extracting soil physical information that exists within crop yield maps to create spatially- and temporally-dense dataset

Ergonomic Standards for Pedestrian Areas for Disabled People: Methodology and Sample Identification

This project is a TRRL research contract, the aim of which is to produce guidance on the design of pedestrian areas and footways for elderly and disabled people. The first part of the project was a literature review and consultation exercise, the objective of which was to identify key impediments for investigation. The second part of the project involved the detailed survey work on the key impediments. This Working Paper reports upon the development of the second part of the project and, in particular, upon the identification of the sample of disabled people to be used in the detailed interview and observation work. The sample identification involved contacting some 3000 disabled people listed in official disability registers, and 250 ablebodied people via on-street interviews. From the disabled sample approximately 500 people were interviewed in order to find out more about their disability and to assess the usefulness of a preliminary disability categorisation system; their activity rate; problems they experience in using pedestrian areas and footways; and their willingness to take part in further stages of the study. From the interviews, a sample of people in each of the revised categories, together with samples of the elderly and the ablebodied, were selected for an observation phase in which those involved were observed completing a movement distance exercise, and using different types of pedestrian facility, in central Leeds

Ergonomic standards for pedestrian areas for disabled people: literature review and consultations

As part of the project for the Transport and Road Research Laboratory concerned with the development of design guidance for pedestrian areas and footways to satisfy the needs of disabled and elderly people, a thorough examination of the literature was required. In addition the literature search was to be complemented by a wide-ranging series of discussions with local authorities, organisations representing the interests of elderly and disabled people, and other interested agencies. This Working Paper sets out the findings of this exercise. The objective of the literature review and the consultations was to identify the key impediments for elderly and disabled people when using pedestrian areas and footways. The current guidelines and standards relating to footways, pedestrianised areas and access to buildings were to be identified and their adequacy commented upon, as were the conflicts such recommendations raise between various groups of disabled people and with able-bodied people. The consultations were intended to provide greater insights into what the literature highlighted, and to suggest possible solutions. The literature review produced over 400 key references and a list of 35 impediments. A more detailed examination of the literature and the consultations reduced this list to six key impediments namely: parking; public transport waiting areas; movement distances; surface conditions; ramps, and information provision. The type and scale of problem created by the above impediments for various groups of disabled and elderly people are discussed, together with their measurement and assessment. The type and adequacy of existing design standards and guidance relating to these impediments are also outlined

Economic Standards for Pedestrian Areas for Disabled People: Results from Observation Work

1.1.1 The Institute for Transport Studies was invited by the Transport and Road Research Laboratory to submit a research proposal, with costs, aimed at establishing suitable "Ergonomic Standards for Pedestrian Areas for Disabled People". The project commenced on 1st July, 1986 and was split into two parts, with part one involving four months' work over the period to 31st December, 1986 and part two finishing on 30th April, 1988. 1.1.2 The -objectives of the study laid down in the design brief by the Transport and Road Research Laboratory were: a) To produce a guide to good practice for the design and maintenance of footways and pedestrianised areas; b) To provide, where possible, recommended standards for design and maintenance. The good practice guide and the recommended standards were to be primarily aimed at disabled people and the elderly, but the requirements of the able-bodied were also to be considered, as were conflicts between the needs of different groups of user. The economic implications of implementation and maintenance were also to be detailed. (Continues..

Economic Standards for Pedestrian Areas for Disabled People: Results of the Initial and Main Interview

1.1.1 The Institute for Transport Studies was invited by the Transport and Road Research Laboratory to submit a research proposal, with costs, aimed at establishing suitable llErgonomic Standards for Pedestrian Areas for Disabled People". The project commenced on 1st July, 1986 and was split into two parts, with part one involving four monthso work over the period to 31st December, 1986 and part two finishing on 30th April, 1988. 1.1.2 The main objectives of the Study laid down in the design brief by the Transport and Road Research Laboratory were: a) To produce a guide to good practice for the design and maintenance of footways and pedestrianised areas; b) To provide, where possible, recommended standards for design and maintenance. The good practice guide and the recommended standards were to be primarily aimed at disabled people and the elderly, but the requirements of the able-bodied were also to be considered, as were conflicts between the needs of different groups of user. The economic implications of implementation and maintenance were also to be detailed