Showing papers by "University of Hertfordshire published in 2007"

The UKIRT Infrared Deep Sky Survey (UKIDSS)

Abstract: Final published version including significant revisions. Twenty four pages, fourteen figures. Original version April 2006; final version published in MNRAS August 2007

Socially intelligent robots: dimensions of human-robot interaction.

Abstract: Social intelligence in robots has a quite recent history in artificial intelligence and robotics. However, it has become increasingly apparent that social and interactive skills are necessary requirements in many application areas and contexts where robots need to interact and collaborate with other robots or humans. Research on human–robot interaction (HRI) poses many challenges regarding the nature of interactivity and ‘social behaviour’ in robot and humans. The first part of this paper addresses dimensions of HRI, discussing requirements on social skills for robots and introducing the conceptual space of HRI studies. In order to illustrate these concepts, two examples of HRI research are presented. First, research is surveyed which investigates the development of a cognitive robot companion. The aim of this work is to develop social rules for robot behaviour (a ‘robotiquette’) that is comfortable and acceptable to humans. Second, robots are discussed as possible educational or therapeutic toys for children with autism. The concept of interactive emergence in human–child interactions is highlighted. Different types of play among children are discussed in the light of their potential investigation in human–robot experiments. The paper concludes by examining different paradigms regarding ‘social relationships’ of robots and people interacting with them.

The SAURON project – IX. A kinematic classification for early‐type galaxies

Abstract: Two-dimensional stellar kinematics of 48 representative elliptical (E) and lenticular (S0) galaxies obtained with the SAURON integral-field spectrograph reveal that early-type galaxies appear in two broad flavours, depending on whether they exhibit clear large-scale rotation or not. We define a new parameter lambda(R) equivalent to / , which involves luminosity-weighted averages over the full two-dimensional kinematic field as a proxy to quantify the observed projected stellar angular momentum per unit mass. We use it as a basis for a new kinematic classification: early-type galaxies are separated into slow and fast rotators, depending on whether they have lambda(R) values within their effective radius R(e) below or above 0.1, respectively. Slow and fast rotators are shown to be physically distinct classes of galaxies, a result which cannot simply be the consequence of a biased viewing angle. Fast rotators tend to be relatively low-luminosity galaxies with M(B) greater than or similar to-20.5. Slow rotators tend to be brighter and more massive galaxies, but are still spread over a wide range of absolute magnitude. Three slow rotators of our sample, among the most massive ones, are consistent with zero rotation. Remarkably, all other slow rotators (besides the atypical case of NGC 4550) contain a large kpc-scale kinematically decoupled core (KDC). All fast rotators (except one galaxy with well-known irregular shells) show well-aligned photometric and kinemetric axes, and small velocity twists, in contrast with most slow rotators which exhibit significant misalignments and velocity twists. These results are supported by a supplement of 18 additional early-type galaxies observed with SAURON. In a companion paper (Paper X), we also show that fast and slow rotators are distinct classes in terms of their orbital distribution. We suggest that gas is a key ingredient in the formation and evolution of fast rotators, and that the slowest rotators are the extreme evolutionary end point reached deep in gravitational potential wells where dissipationless mergers had a major role in the evolution, and for which most of the baryonic angular momentum was expelled outwards. Detailed numerical simulations in a cosmological context are required to understand how to form large-scale KDCs within slow rotators, and more generally to explain the distribution of lambda(R) values within early-type galaxies and the distinction between fast and slow rotators.

Observational evidence for AGN feedback in early-type galaxies

Abstract: The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing

Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law

Abstract: We have studied the relationship between the star formation rate (SFR), surface density, and gas surface density in the spiral galaxy M51a (NGC 5194), using multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS). We introduce a new SFR index based on a linear combination of Hα emission-line and 24 μm continuum luminosities, which provides reliable extinction-corrected ionizing fluxes and SFR densities over a wide range of dust attenuations. The combination of these extinction-corrected SFR densities with aperture synthesis H I and CO maps has allowed us to probe the form of the spatially resolved star formation law on scales of 0.5-2 kpc. We find that the resolved SFR versus gas surface density relation is well represented by a Schmidt power law, which is similar in form and dispersion to the disk-averaged Schmidt law. We observe a comparably strong correlation of the SFR surface density with the molecular gas surface density, but no significant correlation with the surface density of atomic gas. The best-fitting slope of the Schmidt law varies from N = 1.37 to 1.56, with zero point and slope that change systematically with the spatial sampling scale. We tentatively attribute these variations to the effects of areal sampling and averaging of a nonlinear intrinsic star formation law. Our data can also be fitted by an alternative parameterization of the SFR surface density in terms of the ratio of gas surface density to local dynamical time, but with a considerable dispersion.

The SAURON project – X. The orbital anisotropy of elliptical and lenticular galaxies: revisiting the (V/σ, ɛ) diagram with integral‐field stellar kinematics

Abstract: We analyse the orbital distribution of elliptical (E) and lenticular (S0) galaxies using SAURON integral-field stellar kinematics within about one effective (half-light) radius. We construct the anisotropy diagram, which relates the ratio of the ordered and random motion in a galaxy (V/sigma) to its observed ellipticity (epsilon), for the 48 E/S0 galaxies from the SAURON survey. For a subsample of 24 galaxies consistent with axisymmetry, we use three-integral axisymmetric Schwarzschild dynamical models to recover the detailed orbital distribution, and we find good agreement with the anisotropy derived from the (V/sigma, epsilon) diagram. In a companion paper (Paper IX), we show that the early-type galaxies can be subdivided into two classes of systems with or without a significant amount of specific stellar angular momentum. Here, we show that the two classes have different distributions on the (V/sigma, epsilon) diagram. The slow rotators are more common among the most massive systems and are generally classified as E from photometry alone. Those in our sample tend to be fairly round(epsilon less than or similar to 0.3), but can have significant kinematical misalignments, indicating that as a class they are moderately triaxial, and span a range of anisotropies (delta less than or similar to 0.3). The fast rotators are generally fainter and are classified as either E or S0. They can appear quite flattened (epsilon less than or similar to 0.7), do not show significant kinematical misalignments (unless barred or interacting), indicating they are nearly axisymmetric and span an even larger range of anisotropies (delta less than or similar to 0.5). These results are confirmed when we extend our analysis to 18 additional E/S0 galaxies observed with SAURON. The dynamical models indicate that the anisotropy inferred from the (V/sigma, epsilon) diagram is due to a flattening of the velocity ellipsoid in the meridional plane (sigma(R) > sigma(z)), which we quantify with the beta anisotropy parameter. We find a trend of increasing beta for intrinsically flatter galaxies. A number of the fast rotators show evidence for containing a flattened, kinematically distinct component, which in some cases counter-rotates relative to the main galaxy body. These components are generally more metal rich than the galaxy body. All these results support the idea that fast rotators are nearly oblate and contain disc-like components. The role of gas must have been important for their formation. The slow rotators are weakly triaxial. Current collisionless merger models seem unable to explain their detailed observed properties.

Carbon-enhanced Metal-poor Stars. I. Chemical Compositions of 26 Stars*

Abstract: The chemical compositions of 26 metal-poor stars that exhibit strong CH and/or C2 molecular bands are determined. Twenty-two stars in our sample satisfy our definition for carbon-enhanced metal-poor (CEMP) stars based on the carbon abundance ratio ([C/Fe]) and the evolutionary status. In addition, we measure Na abundances for nine known carbon-enhanced stars. Combining our new sample with the results of previous work, we investigate the abundance and evolutionary status of a total of 64 CEMP stars. The following results are obtained: (1) All but one of the 37 stars with [Fe/H] ≥ -2.6 exhibit large excesses of barium ([Ba/Fe] > +0.5), while the other 27 stars with lower metallicity exhibit a large scatter in their barium abundance ratios (-1.2 < [Ba/Fe] < +3.3). (2) A correlation between the carbon and barium abundance ratios ([C/Fe] and [Ba/Fe]) is found in Ba-enhanced objects (comprising 54 stars), suggesting that the origin of the observed carbon excess in Ba-enhanced stars is nucleosynthesis in AGB stars, where the main s-process occurs. (3) The majority of the Ba-enhanced stars have -1.0 < [C/H] < 0.0, and a clear cutoff exists at [C/H] ~ 0, which we take as the limit of carbon enrichment by metal-poor AGB stars. The [C/H] values of Ba-normal stars are relatively low, with a wide distribution. (4) The difference in the distributions of evolutionary status between Ba-enhanced and Ba-normal CEMP stars suggested by our previous work is not statistically confirmed by the present, enlarged sample. (5) Excesses of Na are found in stars with extremely large enhancements of C, N, and Ba, suggesting efficient production of this element by AGB nucleosynthesis. The implications of these results on the origins of carbon in CEMP stars are discussed.

Divergent thinking: Strategies and executive involvement in generating novel uses for familiar objects

Abstract: Original article can be found at: http://www.bps.org.uk/publications/journals/bjp/bjp_home.cfm Copyright The British Psychological Society DOI: 10.1348/096317907X173421

Hot and cold gas accretion and feedback in radio-loud active galaxies

Abstract: We have recently shown that X-ray observations of the population of ‘low-excitation’ radio galaxies, which includes most low-power, Fanaroff‐Riley class I sources as well as some more powerful Fanaroff‐Riley class II objects, are consistent with a model in which the active nuclei of these objects are not radiatively efficient at any waveband. In another recent paper, Allen et al. have shown that Bondi accretion of the hot, X-ray emitting phase of the intergalactic medium (IGM) is sufficient to power the jets of several nearby, low-power radio galaxies at the centres of clusters. In this paper, we combine these ideas and suggest that accretion of the hot phase of the IGM is sufficient to power all low-excitation radio sources, while high-excitation sources are powered by accretion of cold gas that is in general unrelated to the hot IGM. This model explains a number of properties of the radio-loud active galaxy population, and has important implications for the energy input of radio-loud active galactic nuclei into the hot phase of the IGM: the energy supply of powerful high-excitation sources does not have a direct connection to the hot phase.

Estuarine, coastal and marine ecosystem restoration: Confusing management and science – A revision of concepts

Abstract: This review presents recent concepts, understanding and experience of the restoration, recovery and human-mediated modification of estuarine, coastal and marine ecosystems. It shows that these can be divided into four categories: natural recovery from a natural or anthropogenic change (whether adverse or otherwise); anthropogenic interventions in response to a degraded or anthropogenically changed environment; anthropogenic responses to a single stressor; and habitat enhancement or creation. A conceptual framework for restoration and recovery of marine marginal and semi-enclosed areas is presented after exploring and refining the plethora of terms used in restoration science and management. Examples of management action are given including managed realignment and the restoration of docks, biogenic reefs, saltmarsh, seagrass, beaches and upper estuarine water quality. We emphasise that although recovery techniques are worthwhile if they can be carried out, they rarely (if ever) fully replace lost habitat. Moreover, while they may have some success in marginal or semi-enclosed areas such as coastal bays, estuaries and fringing habitats, they are less relevant to open coastal and marine habitats. Therefore the best option available in the latter can only be to remove the stressor, as the cause of any change, to prevent other stressors from operating and to allow the conditions suitable for natural recovery. This review emphasises that whereas some ecological concepts related to restoration are well understood, for example, the nature of ecosystem structure and functioning, others such as carrying capacity, resilience and ecosystem goods and services are still poorly quantified for the marine and estuarine environments. The linking between these ecological concepts and the management framework is also relatively recent but is required to give a holistic approach to understanding, managing and manipulating these environments.

Meanings of methodological individualism

Abstract: Advocacy of 'methodological individualism' is widespread, especially among economists. However, the term is rarely defined with adequate precision and some crucial ambiguities are explored in this article. Among these is the commonplace ambivalence over whether explanations should be in terms of individuals alone, or in terms of individuals plus relations between them. It is shown that a great deal hinges on this subtle and often overlooked distinction in explanantia. In particular, explanations in terms of individuals alone have never, as yet, been achieved. Furthermore, the more feasible version of explanations in terms of individuals plus relations between them amounts to the introduction of social structure alongside individuals in the explanantia. Serious questions remain whether this version warrants the one-sided emphasis on individuals in the term 'methodological individualism'.

Effect of a Collaborative Approach on the Quality of Prescribing for Geriatric Inpatients: A Randomized, Controlled Trial

Abstract: OBJECTIVES: To evaluate the effect of pharmaceutical care provided in addition to acute Geriatric Evaluation and Management (GEM) care on the appropriateness of prescribing. DESIGN: Randomized, controlled trial, with the patient as unit of randomization. SETTING: Acute GEM unit. PARTICIPANTS: Two hundred three patients aged 70 and older. INTERVENTION: Pharmaceutical care provided from admission to discharge by a specialist clinical pharmacist who had direct contacts with the GEM team and patients. MEASUREMENTS: Appropriateness of prescribing on admission, at discharge, and 3 months after discharge, using the Medication Appropriateness Index (MAI), Beers criteria, and Assessing Care of Vulnerable Elders (ACOVE) underuse criteria and mortality, readmission, and emergency visits up to 12 months after discharge. RESULTS: Intervention patients were significantly more likely than control patients to have an improvement in the MAI and in the ACOVE underuse criteria from admission to discharge (odds ratio (OR) 59.1, 95% confidence interval (CI) 54.2‐21.6 and OR 56.1, 95% CI 52.2‐17.0, respectively). The control and intervention groups had comparable improvements in the Beers criteria. CONCLUSION: Pharmaceutical care provided in the context of acute GEM care improved the appropriate use of medicines during the hospital stay and after discharge. This is an important finding, because only limited data exist on the effect of various strategies to improve medication use in elderly inpatients. The present approach has the potential to minimize risk and improve patient outcomes. JA m Geriatr Soc 55:658–665, 2007.

The SCUBA HAlf Degree Extragalactic Survey - III. Identification of radio and mid-infrared counterparts to submillimetre galaxies

Abstract: Determining an accurate position for a submillimetre (submm) galaxy (SMG) is the crucial step that enables us to move from the basic properties of an SMG sample – source counts and 2D clustering – to an assessment of their detailed, multiwavelength properties, their contribution to the history of cosmic star formation and their links with present-day galaxy populations. In this paper, we identify robust radio and/or infrared (IR) counterparts, and hence accurate positions, for over two-thirds of the SCUBA HAlf-Degree Extragalactic Survey (SHADES) Source Catalogue, presenting optical, 24-μm and radio images of each SMG. Observed trends in identification rate have given no strong rationale for pruning the sample. Uncertainties in submm position are found to be consistent with theoretical expectations, with no evidence for significant additional sources of error. Employing the submm/radio redshift indicator, via a parametrization appropriate for radio-identified SMGs with spectroscopic redshifts, yields a median redshift of 2.8 for the radio-identified subset of SHADES, somewhat higher than the median spectroscopic redshift. We present a diagnostic colour–colour plot, exploiting Spitzer photometry, in which we identify regions commensurate with SMGs at very high redshift. Finally, we find that significantly more SMGs have multiple robust counterparts than would be expected by chance, indicative of physical associations. These multiple systems are most common amongst the brightest SMGs and are typically separated by 2–6 arcsec, ~15–50/ sin i kpc at z∼ 2, consistent with early bursts seen in merger simulations.

Methodology & Themes of Human-Robot Interaction: A Growing Research Field

Abstract: This article discusses challenges of Human-Robot Interaction, which is a highly inter- and multidisciplinary area. Themes that are important in current research in this lively and growing field are identified and selected work relevant to these themes is discussed.

The Development of Accounting Quality of IAS and IFRS Over Time: The Case of Germany

Abstract: We examine the characteristics of accounting numbers using a sample of German companies reporting under IAS (2000-2002), and IFRS (2003-2004) and (2005-2006). We investigate the change in accounting quality during these time periods as IASB revises and issues new standards. Contrary to expectations, we find that earnings and book value of equity are less value relevant during the IFRS periods than the IAS period. The findings on earnings smoothing and timely loss recognition corroborate the value relevance test. Our results suggest that firms in the IFRS periods manage earnings more and do not recognize losses in a timely manner as compared to the IAS period. These results are reasonably robust even when we remove new and less experienced adopters of IFRS.

Temperature profiles of a representative sample of nearby X-ray galaxy clusters

Abstract: Context. A study of the structural and scaling properties of the temperature distribution of the hot, X-ray emitting intra-cluster medium of galaxy clusters, and its dependence on dynamical state, can give insights into the physical processes governing the formation and evolution of structure. Aims. Accurate temperature measurements are a pre-requisite for a precise knowledge of the thermodynamic properties of the intra-cluster medium. Methods. We analyse the X-ray temperature profiles from XMM-Newton observations of 15 nearby (z < 0.2) clusters, drawn from a statistically representative sample. The clusters cover a temperature range from 2.5 keV to 8.5 keV, and present a variety of X-ray morphologies. We derive accurate projected temperature profiles to ∼0.5 R 200 , and compare structural properties (outer slope, presence of cooling core) with a quantitative measure of the X-ray morphology as expressed by power ratios. We also compare the results to recent cosmological numerical simulations. Results. Once the temperature profiles are scaled by an average cluster temperature (excluding the central region) and the estimated virial radius, the profiles generally decline in the region 0.1 R 200 ≤ R ≤ 0.5 R 200 . The central regions show the largest scatter, attributable mostly to the presence of cool core clusters. There is good agreement with numerical simulations outside the core regions. We find no obvious correlations between power ratio and outer profile slope. There may however be a weak trend with the existence of a cool core, in the sense that clusters with a central temperature decrement appear to be slightly more regular. Conclusions. The present results lend further evidence to indicate that clusters are a regular population, at least outside the core region.

The representative XMM-Newton cluster structure survey (REXCESS) of an X-ray luminosity selected galaxy cluster sample

Abstract: Context.The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge of the statistics of galaxy cluster structure, and of the scaling relations between observables and cluster mass.

Extra-articular manifestations and complications of rheumatoid arthritis

Abstract: Rheumatoid arthritis (RA) is a systemic inflammatory disease that can involve other tissues and organs as well as synovial joints. This chapter reviews the clinical aspects of extra-articular RA, from the early descriptions in rheumatology texts to reports from more recent cross-sectional and inception cohort studies. There is no agreed classification for these manifestations and, because criteria and definitions vary so much, this report includes not only the classic extra-articular features but also the non-articular complications of RA, for example normochromic normocytic anaemia and chronic leg ulcers, and the important disease-associated comorbidities, including non-Hodgkin's lymphoma, ischaemic heart disease and osteoporosis. Incidence and frequency figures for extra-articular RA vary according to study design. Nodules are the most common extra-articular feature, and are present in up to 30%; many of the other classic features occur in 1% or less in normal clinic settings. Sjogren's syndrome, anaemia of chronic disease and pulmonary manifestations are relatively common - in 6-10% - are frequently present in early disease and are all related to worse outcomes measures of rheumatoid disease, in particular functional impairment and mortality. Currently, there are no reliable predictors for these features in early RA, although they are associated with men, smokers, more severe joint disease, worse function, high levels of inflammatory markers, and the presence of rheumatoid factor (RF), antinuclear antibodies (ANA) and the RA HLA-related shared epitope. Many of these manifestations are related to the more active and severe RA, so early and more aggressive RA drug therapies are being employed and, although evidence from randomised studies is not available, this approach would seem appropriate in view of the adverse effect of extra-articular manifestations on RA outcomes. Unfortunately, specific therapies for extra-articular manifestations of RA are largely disappointing or unavailable, except for steroids and cyclophosphamide for vasculitis. The place for biological therapies is still not clear. Pulmonary fibrosis in RA has a poor prognosis whether treated with large doses of steroids, cytotoxic or disease modifying drugs like cyclosporine, or biologics. In summary, extra-articular features and non-articular complications of RA are common and are generally related to worse disease. They need to be recognised early and managed promptly.

The United Kingdom Infrared Telescope Infrared Deep Sky Survey First Data Release

Abstract: The First Data Release (DR1) of the United Kingdom Infrared Telescope Infrared Deep Sky Survey (UKIDSS) took place on 2006 July 21. The UKIDSS is a set of five large near-infrared surveys, covering a complementary range of areas, depths and Galactic latitudes. The DR1 is the first large release of survey-quality data from the UKIDSS and includes 320 deg 2 of multicolour data to (Vega) K = 18, complete (depending on the survey) in three to five bands from the set ZYJHK, together with 4 deg 2 of deep JK data to an average depth K = 21. In addition, the release includes a similar quantity of data with incomplete filter coverage. In JHK, in regions of low extinction, the photometric uniformity of the calibration is better than 0.02 mag in each band. The accuracy of the calibration in ZY remains to be quantified, and the same is true of JHK in regions of high extinction. The median image full width at half-maximum across the data set is 0.82 arcsec. We describe changes since the Early Data Release in the implementation, pipeline and calibration, quality control, and archive procedures. We provide maps of the areas surveyed, and summarize the contents of each of the five surveys in terms of filters, areas and depths. The DR1 marks completion of 7 per cent of the UKIDSS seven-year goals.

Institutions and Individuals: Interaction and Evolution

Abstract: The conceptualization of the relation between individual and structure is central to social science. After making some key definitions, this paper overviews some recent developments in the social theory of structure and agency, and makes a novel addition, based on a concept of habit derived from pragmatism and Veblenian institutional economics. Processes of habituation provide a mechanism of ‘reconstitutive downward causation’ where institutional circumstances may affect individual preferences. Finally, special characteristics of organizations are discussed, endorsing an evolutionary analytical approach that combines insights from both evolutionary economics and organization science.

Cervical spondylosis and neck pain

Abstract: Most patients who present with neck pain have “non-specific (simple) neck pain,” where symptoms have a postural or mechanical basis. Aetiological factors are poorly understoodw1 and are usually multifactorial, including poor posture, anxiety, depression, neck strain, and sporting or occupational activities.w2 Neck pain after whiplash injury also fits into this category, provided no bony injury or neurological deficit is present.w3 When mechanical factors are prominent, the condition is often referred to as “cervical spondylosis,” although the term is often applied to all non-specific neck pain. Mechanical and degenerative factors are more likely to be present in chronic neck pain. In cervical spondylosis, degenerative changes start in the intervertebral discs with osteophyte formation and involvement of adjacent soft tissue structures. Many people over 30 show similar abnormalities on plain radiographs of the cervical spine, however, so the boundary between normal ageing and disease is difficult to define.w4 Even severe degenerative changes are often asymptomatic, but can lead to neck pain, stiffness, or neurological complications. I will concentrate on the diagnosis of cervical spondylosis and the evidence available for the different treatments. I will also mention some practical measures that are thought to be important but have not yet been studied. Specific conditions like fibromyalgia, disc prolapse, and whiplash will not be considered, although some patients with these conditions may have been included in therapeutic studies. #### Summary points

Properties of Bars and Bulges in the Hubble Sequence

Abstract: Properties of bars and bulges in the Hubble sequence are discussed, based on the analysis of 216 disk galaxies (S0s and spirals from NIRS0S and OSUBGS surveys, respectively). For that purpose we have collected together, and completed when necessary, the various analysis we have previously made separately for early and late types. We find strong photometric and kinematic evidence of pseudobulges in the S0-S0/a galaxies: their bulges are on average fairly exponential, inner disks are common (in 56%), and in many of the galaxies the bulges are rotationally supported. This would be difficult to understand in such gas poor galaxies as in S0s, i f these pseudobulge candidates were formed by star formation in the disk in a a similar manner as in spirals. A more likely explanation is that pseudobulges in the early-type galaxies are bar-related structures, connected to the evolution of bars, which interpretation is supported by our Fourier analysis and structural decompositions. Bars in the early-type galaxies are found to have many characteristics of evolved systems: (1) they have flat-top/double peaked Fourier amplitude profiles, (2) bars have typically sharp outer cut-offs, (3) the higher Fourier modes appear in the amplitude profiles, and (4) many bars have also ansae-type morphologies. We show the distributions of bar strength in different Hubble type bins using four bar strength indicators, Qg, A2, fbar and the bar length, which are expected to give important clues for understanding the mechanism of how bars evolve.

A typology of educationally focused medical simulation tools.

Abstract: Background: The concept of simulation as an educational tool in healthcare is not a new idea but its use has really blossomed over the last few years. This enthusiasm is partly driven by an attempt to increase patient safety and also because the technology is becoming more affordable and advanced.Aims: Simulation is becoming more commonly used for initial training purposes as well as for continuing professional development, but people often have very different perceptions of the definition of the term simulation, especially in an educational context. This highlights the need for a clear classification of the technology available but also about the method and teaching approach employed. The aims of this paper are to discuss the current range of simulation approaches and propose a clear typology of simulation teaching aids.Method: Commonly used simulation techniques have been identified and discussed in order to create a classification that reports simulation techniques, their usual mode of delivery, the sk...

Multiwaveband Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Correlated Polarization Behavior

Abstract: We report on multifrequency linear polarization monitoring of 15 active galactic nuclei containing highly relativistic jets with apparent speeds from ~4c to >40c. The measurements were obtained at optical, 1 mm, and 3 mm wavelengths, and at 7 mm with the Very Long Baseline Array. The data show a wide range in degree of linear polarization among the sources, from 30%, and interday polarization variability in individual sources. The polarization properties suggest separation of the sample into three groups with low, intermediate, and high variability of polarization in the core at 7 mm (LVP, IVP, and HVP, respectively). The groups are partially associated with the common classification of active galactic nuclei as radio galaxies and quasars with low optical polarization (LVP), BL Lacertae objects (IVP), and highly optically polarized quasars (HVP). Our study investigates correlations between total flux, fractional polarization, and polarization position angle at the different wavelengths. We interpret the polarization properties of the sources in the sample through models in which weak shocks compress turbulent plasma in the jet. The differences in the orientation of sources with respect to the observer, jet kinematics, and abundance of thermal matter external to the jet near the core can account for the diversity in the polarization properties. The results provide strong evidence that the optical polarized emission originates in shocks, most likely situated between the 3 and 7 mm VLBI cores. They also support the idea that the 1 mm core lies at the edge of the transition zone between electromagnetically dominated and turbulent hydrodynamic sections of the jet.

The cabbage aphid: a walking mustard oil bomb.

Abstract: The cabbage aphid, Brevicoryne brassicae, has developed a chemical defence system that exploits and mimics that of its host plants, involving sequestration of the major plant secondary metabolites (glucosinolates). Like its host plants, the aphid produces a myrosinase (beta-thioglucoside glucohydrolase) to catalyse the hydrolysis of glucosinolates, yielding biologically active products. Here, we demonstrate that aphid myrosinase expression in head/thoracic muscle starts during embryonic development and protein levels continue to accumulate after the nymphs are born. However, aphids are entirely dependent on the host plant for the glucosinolate substrate, which they store in the haemolymph. Uptake of a glucosinolate (sinigrin) was investigated when aphids fed on plants or an in vitro system and followed a different developmental pattern in winged and wingless aphid morphs. In nymphs of the wingless aphid morph, glucosinolate level continued to increase throughout the development to the adult stage, but the quantity in nymphs of the winged form peaked before eclosion (at day 7) and subsequently declined. Winged aphids excreted significantly higher amounts of glucosinolate in the honeydew when compared with wingless aphids, suggesting regulated transport across the gut. The higher level of sinigrin in wingless aphids had a significant negative impact on survival of a ladybird predator. Larvae of Adalia bipunctata were unable to survive when fed adult wingless aphids from a 1% sinigrin diet, but survived successfully when fed aphids from a glucosinolate-free diet (wingless or winged), or winged aphids from 1% sinigrin. The apparent lack of an effective chemical defence system in adult winged aphids possibly reflects their energetic investment in flight as an alternative predator avoidance mechanism.

Adjustment to colostomy: stoma acceptance, stoma care self‐efficacy and interpersonal relationships

Abstract: ‘The definitive version is available at www.blackwell-synergy.com.’ Copyright Blackwell Publishing. DOI: 10.1111/j.1365-2648.2007.04446.x