Showing papers by "University of Bath published in 2008"

Looking at, looking up or keeping up with people?: motives and use of facebook

Abstract: This paper investigates the uses of social networking site Facebook, and the gratifications users derive from those uses. In the first study, 137 users generated words or phrases to describe how they used Facebook, and what they enjoyed about their use. These phrases were coded into 46 items which were completed by 241 Facebook users in Study 2. Factor analysis identified seven unique uses and gratifications: social connection, shared identities, content, social investigation, social network surfing and status updating. User demographics, site visit patterns and the use of privacy settings were associated with different uses and gratifications.

Employee attributions of the “why” of hr practices: their effects on employee attitudes and behaviors, and customer satisfaction

Abstract: The construct of human resource (HR) attributions is introduced. We argue that the attributions that employees make about the reasons why management adopts the HR practices that it does have consequences for their attitudes and behaviors, and ultimately, unit performance. Drawing on the strategic HR literature, we propose a typology of 5 HR-attribution dimensions. Utilizing data collected from a service firm, we show that employees make varying attributions for the same HR practices, and that these attributions are differentially associated with commitment and satisfaction. In turn, we show that these attitudes become shared within units and that they are related to unit-level organizational citizenship behaviors and customer satisfaction. Findings and implications are discussed.

Does it pay to be different? An analysis of the relationship between corporate social and financial performance

Abstract: This study explores the relationship between corporate social performance (CSP) and corporate financial performance (CFP) within the context of a specific component of CSP: corporate charitable giving. A model of the determinants of the extent of corporate charitable giving is estimated and used as the basis of a classification that groups firms according to the difference between their actual and their predicted intensity of gift giving. The financial performance attributes of the classification are explored. We found that firms with both unusually high and low CSP have higher financial performance than other firms, with unusually poor social performers doing best in the short run and unusually good social performers doing best over longer time horizons. Copyright © 2008 John Wiley & Sons, Ltd. ABSTRACT FROM AUTHOR

Prediction of the distribution of Arctic-nesting pink-footed geese under a warmer climate scenario

Abstract: Global climate change is expected to shift species ranges polewards, with a risk of range contractions and population declines of especially high-Arctic species. We built species distribution models for Svalbard-nesting pink-footed geese to relate their occurrence to environmental and climatic variables, and used the models to predict their distribution under a warmer climate scenario. The most parsimonious model included mean May temperature, the number of frost-free months and the proportion of moist and wet mossdominated vegetation in the area. The two climate variables are indicators for whether geese can physiologically fulfil the breeding cycle or not and the moss vegetation is an indicator of suitable feeding conditions. Projections of the distribution to warmer climate scenarios propose a large north- and eastward expansion of the potential breeding range on Svalbard even at modest temperature increases (1 and 21C increase in summer temperature, respectively). Contrary to recent suggestions regarding future distributions of Arctic wildlife, we predict that warming may lead to a further growth in population size of, at least some, Arctic breeding geese.

Dye-sensitized solar cells based on oriented TiO2 nanotube arrays: transport, trapping, and transfer of electrons.

Abstract: Dye-sensitized solar cells fabricated using ordered arrays of titania nanotubes (tube lengths 5, 10, and 20 microm) grown on titanium have been characterized by a range of experimental methods. The collection efficiency for photoinjected electrons in the cells is close to 100% under short circuit conditions, even for a 20 microm thick nanotube array. Transport, trapping, and back transfer of electrons in the nanotube cells have been studied in detail by a range of complementary experimental techniques. Analysis of the experimental results has shown that the electron diffusion length (which depends on the diffusion coefficient and lifetime of the photoinjected electrons) is of the order of 100 microm in the titania nanotube cells. This is consistent with the observation that the collection efficiency for electrons is close to 100%, even for the thickest (20 microm) nanotube films used in the study. The study revealed a substantial discrepancy between the shapes of the electron trap distributions measured experimentally using charge extraction techniques and those inferred indirectly from transient current and voltage measurements. The discrepancy is resolved by introduction of a numerical factor to account for non-ideal thermodynamic behavior of free electrons in the nanostructured titania.

Factors influencing the quality of corporate environmental disclosure

Abstract: Many firms choose to communicate their environmental strategies through voluntary environmental disclosures. This paper examines patterns in the quality of voluntary environmental disclosures made by a sample of around 450 large UK companies drawn from a diverse range of industrial sectors. The analysis distinguishes between five facets of quality, including the disclosure of group-wide environmental policies, environmental impact targets and an environmental audit. We examine how the decisions firms face regarding each facet of quality are determined by firm and industry characteristics, and find the quality of disclosure to be determined by a firm's size and the nature of its business activities. Specifically, we find high quality disclosure to be primarily associated with larger firms and those in sectors most closely related to environmental concerns. In contrast to several recent contributions, we find that the media exposure of companies plays no role in stimulating voluntary disclosures. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.

Fast stable direct fitting and smoothness selection for generalized additive models

Abstract: Summary. Existing computationally efficient methods for penalized likelihood generalized addi tive model fitting employ iterative smoothness selection on working linear models (or working mixed models). Such schemes fail to converge for a non-negligible proportion of models, with failure being particularly frequent in the presence of concurvity. If smoothness selection is per formed by optimizing 'whole model' criteria these problems disappear, but until now attempts to do this have employed finite-difference-based optimization schemes which are computationally inefficient and can suffer from false convergence. The paper develops the first computationally efficient method for direct generalized additive model smoothness selection. It is highly sta ble, but by careful structuring achieves a computational efficiency that leads, in simulations, to lower mean computation times than the schemes that are based on working model smoothness selection. The method also offers a reliable way of fitting generalized additive mixed models.

Highly confined guiding of terahertz surface plasmon polaritons on structured metal surfaces

Abstract: Metamaterials are artificial materials with subwavelength structure1 that enable the translation of magnetic2 and electric responses3 into spectral regions not accessible through naturally occurring materials. Here, we report direct measurements of the propagation and confinement of terahertz electromagnetic surface modes tightly bound to flat plasmonic metamaterials that consist of metal surfaces decorated with two-dimensional arrays of subwavelength-periodicity pits. These modes are surface plasmon polaritons with an effective plasma frequency controlled entirely by the surface geometry4. The mode spectrum and penetration depth into air demonstrate strong wavelength-scale energy confinement to the surface below the electromagnetic band edge; this is in stark contrast to the very weak confinement found at flat metal surfaces in this spectral regime. The results are in good agreement with analytical and numerical models of surface plasmon polaritons propagating on structured perfect-conductor surfaces, and imply that plasmonic metamaterials could help miniaturize optical components or lead to improved chemical or biochemical sensors.

Lithium Battery Materials LiMPO4 (M = Mn, Fe, Co, and Ni): Insights into Defect Association, Transport Mechanisms, and Doping Behavior

Abstract: The defect chemistry, doping behavior, and ion migration in olivine-type materials LiMPO4 (M = Mn, Fe, Co, and N) are investigated by atomistic simulation techniques. The most favorable intrinsic defect type is found to be the cation antisite defect, in which Li and M ions exchange positions. Li migration is found to occur preferentially down [010] channels, following a curved trajectory. Defect association or binding energies for pair clusters composed of combinations of lithium vacancies, antisite cations, and small polaron species are investigated. Migration energies for divalent antisite cations on Li sites suggest that such defects would impede Li diffusion in LiMPO4 to varying degrees. Calculation of dopant substitution energies for cations with charges +1 to +5 indicate that supervalent doping (e.g., Ga3+, Ti4+, Nb5+) on either Li or M sites is energetically unfavorable and does not result in a large increase in electronic (small polaron) species.

Acceptance and values-based action in chronic pain: A study of treatment effectiveness and process.

Abstract: Developing approaches within cognitive behavioral therapy are increasingly process-oriented and based on a functional and contextual framework that differs from the focus of earlier work. The present study investigated the effectiveness of acceptance and commitment therapy (S. C. Hayes, K. Strosahl, & K. G. Wilson, 1999) in the treatment of chronic pain and also examined 2 processes from this model, acceptance and values-based action. Participants included 171 completers of an interdisciplinary treatment program, 66.7% of whom completed a 3-month follow-up assessment as well. Results indicated significant improvements for pain, depression, pain-related anxiety, disability, medical visits, work status, and physical performance. Effect size statistics were uniformly medium or larger. According to reliable change analyses, 75.4% of patients demonstrated improvement in at least one key domain. Both acceptance of pain and values-based action improved, and increases in these processes were associated with improvements in the primary outcome domains.

Over 4000 nm bandwidth of mid-IR supercontinuum generation in sub-centimeter segments of highly nonlinear tellurite PCFs.

Abstract: We report broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber (PCF). We pump the fiber at telecommunication wavelengths by using 1550 nm, 100 fs pulses of energy E=1.9 nJ. When coupled in the PCF, these pulses result in a supercontinuum (SC) bandwidth of 4080 nm extending from 789 to 4870 nm measured at 20 dBm below the peak spectral power. This bandwidth is comparable or in excess of previously reported spectra for other nonlinear glass fiber formulations despite the significantly shorter fiber length. In addition, besides offering a convenient pump wavelength, short fiber lengths enable smoother SC spectra, lower dispersion, and reduced material absorption at longer wavelengths making the use of this PCF particularly interesting.

Statistical Methods with Varying Coefficient Models.

Abstract: The varying coefficient models are very important tool to explore the dynamic pattern in many scientific areas, such as economics, finance, politics, epidemiology, medical science, ecology and so on. They are natural extensions of classical parametric models with good interpretability and are becoming more and more popular in data analysis. Thanks to their flexibility and interpretability, in the past ten years, the varying coefficient models have experienced deep and exciting developments on methodological, theoretical and applied sides. This paper gives a selective overview on the major methodological and theoretical developments on the varying coefficient models.

Making sense of sensemaking narratives

Abstract: This article analyses the agreed and discrepant sensemaking of members of a project team. Embedded in a narratological approach to sensemaking research, we argue that before scholars may be able to understand in detail how agreements are reached and action becomes coordinated, we need first to take seriously the proposition that sensemaking occurs in the context of individuals' idiosyncratic efforts at identity construction. This, we suggest, means attending to the narratives that actors tell about their work and self both for others and their selves. The key research contribution that we make is to demonstrate how work on `impression management' and `attributional egotism' may be employed in order to account for discrepant sensemaking. This is important in the context of a literature that has left relatively unexplored the reasons why people interpret differently experiences they have in common.

Time series forecasting with neural networks: a comparative study using the air line data

Abstract: Summary. This case-study fits a variety of neural network (NN) models to the well-known airline data and compares the resulting forecasts with those obtained from the Box‐Jenkins and Holt‐ Winters methods. Many potential problems in fitting NN models were revealed such as the possibility that the fitting routine may not converge or may converge to a local minimum. Moreover it was found that an NN model which fits well may give poor out-of-sample forecasts. Thus we think it is unwise to apply NN models blindly in ‘black box’ mode as has sometimes been suggested. Rather, the wise analyst needs to use traditional modelling skills to select a good NN model, e.g. to select appropriate lagged variables as the ‘inputs’. The Bayesian information criterion is preferred to Akaike’s information criterion for comparing different models. Methods of examining the response surface implied by an NN model are examined and compared with the results of alternative nonparametric procedures using generalized additive models and projection pursuit regression. The latter imposes less structure on the model and is arguably easier to understand.

The cancer chemopreventive actions of phytochemicals derived from glucosinolates

Abstract: This article reviews the mechanisms by which glucosinolate breakdown products are thought to inhibit carcinogenesis. It describes how isothiocyanates, thiocyanates, nitriles, cyano-epithioalkanes and indoles are produced from glucosinolates through the actions of myrosinase, epithiospecifier protein and epithiospecifier modifier protein released from cruciferous vegetables during injury to the plant. The various biological activities displayed by these phytochemicals are described. In particular, their abilities to induce cytoprotective genes, mediated by the Nrf2 (NF-E2 related factor 2) and AhR (arylhydrocarbon receptor) transcription factors, and their abilities to repress NF-κB (nuclear factor-κB) activity, inhibit histone deacetylase, and inhibit cytochrome P450 are outlined. Isothiocyanates appear to alter gene expression through modification of critical thiols in regulatory proteins such as Keap1 (Kelch-like ECH-associated protein 1) or IKK (IκB kinase), causing activation of Nrf2 and inactivation of NF-κB, respectively. Certain indoles act as ligands for AhR. Isothiocyanates and indoles are also capable of affecting cell cycle arrest and stimulating apoptosis. The mechanisms responsible for these anti-proliferative responses are discussed.

Developing transition pathways for a low carbon electricity system in the UK

Abstract: This paper describes the approach to developing transition pathways for a low carbon electricity system in the UK, being pursued in a major new research project The project aims (a) to learn from past transitions to help explore future transitions and what might enable or avoid them; (b) to design and evaluate transition pathways towards alternative socio-technical energy systems and infrastructures for a low carbon future; and (c) to understand and where appropriate model the changing roles, influences and opportunities of large and small 'actors' in the dynamics of transitions The paper describes the approach being taken, which builds on the work of Dutch researchers on transitions and transition management using a multi-level framework of niches, socio-technical regime and landscape It also outlines its application to the case of transition pathways to a regime dominated by local distributed electricity generation, including the evolution of the physical and institutional infrastructure changes, and the roles of actors, both large, eg multinational energy supply and distribution companies, national governments, major investors, and small, eg households, innovators and entrepreneurs

New routes to sustainable photovoltaics: evaluation of Cu2ZnSnS4 as an alternative absorber material

Abstract: Thin film heterojunction solar cells based on chalcopyrites such as Cu(In,Ga)Se2 have achieved impressive efficiencies. However concern about the long term sustainability of photovoltaics based on scarce or expensive raw materials has prompted the search for alternative absorber materials. In this work, films of the p-type absorber Cu2ZnSnS4 (CZTS) were prepared by electroplating metallic precursors sequentially onto a molybdenum-coated glass substrate followed by an nealing in a sulfur atmosphere. The polycrystalline CZTS films were characterized by photoelectrochemical methods, which showed films were p-type with doping densities of the order of 1016 cm–3 and a band gap of 1.49 eV, close to the optimum value for terrestrial solar energy conversion. Preliminary results obtained for solar cells fabricated with this material are promising. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The physical demands of elite English rugby union

Abstract: The aim of this study was to assess the physical demands of elite English rugby union match-play. Player movements were captured by five distributed video cameras and then reconstructed on a two-dimensional plane representing the pitch. Movements based on speeds were categorized as standing, walking, jogging, and medium-intensity running (low-intensity activity), and high-intensity running, sprinting, and static exertion (scrummaging, rucking, mauling, and tackling) (high-intensity activity). Position groups were defined as forwards (tight and loose) and backs (inside and outside). Backs travelled more total distance than forwards (6127 m, s = 724 vs. 5581 m, s = 692; P < 0.05) and greater distances in walking (2351 m, s = 287 vs. 1928 m, s = 2342; P < 0.001) and high-intensity running (448 m, s = 149 vs. 298 m, s = 107; P < 0.05). Forwards performed more high-intensity activity than backs (9:09 min:s, s = 1:39 vs. 3:04 min:s, s = 1:01; P < 0.001), which was attributable to more time spent in sta...