Showing papers by "University of Exeter published in 2006"

The James Webb Space Telescope

Abstract: The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth–Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < ; < 5.0 μ m, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < ; < 29 μ m. The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations. To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities.

Switching from insulin to oral sulfonylureas in patients with diabetes due to Kir6.2 mutations.

Abstract: Background Heterozygous activating mutations in KCNJ11, encoding the Kir6.2 subunit of the ATP-sensitive potassium (KATP) channel, cause 30 to 58 percent of cases of diabetes diagnosed in patients under six months of age. Patients present with ketoacidosis or severe hyperglycemia and are treated with insulin. Diabetes results from impaired insulin secretion caused by a failure of the beta-cell KATP channel to close in response to increased intracellular ATP. Sulfonylureas close the KATP channel by an ATP-independent route. Methods We assessed glycemic control in 49 consecutive patients with Kir6.2 mutations who received appropriate doses of sulfonylureas and, in smaller subgroups, investigated the insulin secretory responses to intravenous and oral glucose, a mixed meal, and glucagon. The response of mutant KATP channels to the sulfonylurea tolbutamide was assayed in xenopus oocytes. Results A total of 44 patients (90 percent) successfully discontinued insulin after receiving sulfonylureas. The extent of ...

Fishing, Trophic Cascades, and the Process of Grazing on Coral Reefs

Abstract: Since the mass mortality of the urchin Diadema antillarum in 1983, parrotfishes have become the dominant grazer on Caribbean reefs. The grazing capacity of these fishes could be impaired if marine reserves achieve their long-term goal of restoring large consumers, several of which prey on parrotfishes. Here we compare the negative impacts of enhanced predation with the positive impacts of reduced fishing mortality on parrotfishes inside reserves. Because large-bodied parrotfishes escape the risk of predation from a large piscivore (the Nassau grouper), the predation effect reduced grazing by only 4 to 8%. This impact was overwhelmed by the increase in density of large parrotfishes, resulting in a net doubling of grazing. Increased grazing caused a fourfold reduction in the cover of macroalgae, which, because they are the principal competitors of corals, highlights the potential importance of reserves for coral reef resilience.

Surface plasmon–polariton length scales: a route to sub-wavelength optics

Abstract: We look at four length scales associated with the surface plasmon–polariton (SPP) modes in the visible and near-infrared. We examine some of the consequences of these length scales for exploiting surface plasmon–polariton modes as a means to provide sub-wavelength optics. The four length scales discussed are the SPP wavelength, the SPP propagation distance, and the penetration depths of the field associated with the SPP into the dielectric and metal media that bound the interface that supports the SPP. Length scales spanning seven orders of magnitude, from nanometres to centimetres, are of relevance to SPPs. This paper concludes by identifying some of the challenges that lie ahead.

Politics of Piety: The Islamic Revival and the Feminist Subject

Abstract: Politics of Piety: The Islamic Revival and the Feminist Subject. Saba Mahmood. Princeton: Princeton University Press, 2005. 233 pages.

Autophagic Fungal Cell Death Is Necessary for Infection by the Rice Blast Fungus

Abstract: Rice blast is caused by the fungus Magnaporthe grisea, which elaborates specialized infection cells called appressoria to penetrate the tough outer cuticle of the rice plant Oryza sativa. We found that the formation of an appressorium required, sequentially, the completion of mitosis, nuclear migration, and death of the conidium (fungal spore) from which the infection originated. Genetic intervention during mitosis prevented both appressorium development and conidium death. Impairment of autophagy, by the targeted mutation of the MgATG8 gene, arrested conidial cell death but rendered the fungus nonpathogenic. Thus, the initiation of rice blast requires autophagic cell death of the conidium.

Do Precious Metals Shine? An Investment Perspective

Abstract: The investment role of precious metals in financial markets is investigated by analysis of daily data for gold, platinum, and silver from 1976 to 2004. All three precious metals have low correlations with stock index returns, which suggests that these metals may provide diversification within broad investment portfolios. Moreover, the data reveal that all three precious metals have some hedging capability, particularly during periods of "abnormal" stock market volatility. Financial portfolios that contain precious metals perform significantly better than standard equity portfolios.

Stressing the group: social identity and the unfolding dynamics of responses to stress.

Abstract: Participants in the British Broadcasting Corporation (BBC) prison study were randomly assigned to high-status (guard) and low-status (prisoner) groups. Structural interventions increased the prisoners' sense of shared group identity and their willingness to challenge the power of the guards. Psychometric, physiological, behavioral, and observational data support the hypothesis that identity-based processes also affected participants' experience of stress. As prisoners' sense of shared identity increased, they provided each other with more social support and effectively resisted the adverse effects of situational stressors. As guards' sense of shared identity declined, they provided each other with less support and succumbed to stressors. Findings support an integrated social identity model of stress that addresses intragroup and intergroup dynamics of the stress process.

A comparative study of disc–planet interaction

Abstract: We perform numerical simulations of a disc-planet system using various grid-based and smoothed particle hydrodynamics (SPH) codes. The tests are run for a simple setup where Jupiter and Neptune mass planets on a circular orbit open a gap in a protoplanetary disc during a few hundred orbital periods. We compare the surface density contours, potential vorticity and smoothed radial profiles at several times. The disc mass and gravitational torque time evolution are analysed with high temporal resolution. There is overall consistency between the codes. The density profiles agree within about 5 per cent for the Eulerian simulations. The SPH results predict the correct shape of the gap although have less resolution in the low-density regions and weaker planetary wakes. The disc masses after 200 orbital periods agree within 10 per cent. The spread is larger in the tidal torques acting on the planet which agree within a factor of 2 at the end of the simulation. In the Neptune case, the dispersion in the torques is greater than for Jupiter, possibly owing to the contribution from the not completely cleared region close to the planet.

Star formation through gravitational collapse and competitive accretion

Abstract: Competitive accretion, a process to explain the origin of the initial mass function (IMF), occurs when stars in a common gravitational potential accrete from a distributed gaseous component. Stars located near the centre of the potential benefit from the gravitational attraction of the full potential and accrete at much higher rates than do isolated stars. We show that concerns recently raised on the efficiency of competitive accretion are incorrect as they use globally averaged properties which are inappropriate for the detailed physics of a forming stellar cluster. A full treatment requires a realistic treatment of the cluster potential, the distribution of turbulent velocities and gas densities. Accreting gas does not travel at the global virial velocity of the system due to the velocity-sizescale relation inherent in turbulent gas and due to the lower velocity dispersion of small-N clusters in which much of the accretion occurs. Accretion occurs due to the effect of the local potential in funnelling gas down to the centre. Stars located in the gas-rich centres of such systems initially accrete from low relative velocity gas attaining larger masses before needing to accrete the higher velocity gas. Stars not in the centres of such potentials, or that enter the cluster later when the velocity dispersion is higher, do not accrete significantly and thus retain their low masses. In competitive accretion, most stars do not continue to accrete significantly such that their masses are set from the fragmentation process. It is the few stars which continue to accrete that become higher-mass stars. Competitive accretion is therefore likely to be responsible for the formation of higher-mass stars and can explain the mass distribution, mass segregation and binary frequency of these stars. Global kinematics of competitive accretion models include large-scale mass infall, with mean inflow velocities of the order of ≈0.5 km s -1 at scales of 0.5 pc, but infalling signatures are likely to be confused by the large tangential velocities and the velocity dispersion present. Finally, we discuss potential limitations of competitive accretion and conclude that competitive accretion is currently the most likely model for the origin of the high-mass end of the IMF.

Money as tool, money as drug: The biological psychology of a strong incentive

Abstract: Why are people interested in money? Specifically, what could be the biological basis for the extraordinary incentive and reinforcing power of money, which seems to be unique to the human species? We identify two ways in which a commodity which is of no biological significance in itself can become a strong motivator. The first is if it is used as a tool, and by a metaphorical extension this is often applied to money: it is used instrumentally, in order to obtain biologically relevant incentives. Second, substances can be strong motivators because they imitate the action of natural incentives but do not produce the fitness gains for which those incentives are instinctively sought. The classic examples of this process are psychoactive drugs, but we argue that the drug concept can also be extended metaphorically to provide an account of money motivation. From a review of theoretical and empirical literature about money, we conclude that (i) there are a number of phenomena that cannot be accounted for by a pure Tool Theory of money motivation; (ii) supplementing Tool Theory with a Drug Theory enables the anomalous phenomena to be explained; and (iii) the human instincts that, according to a Drug Theory, money parasitizes include trading (derived from reciprocal altruism) and object play.

The Impact Of Exploiting Grazers (Scaridae) On The Dynamics Of Caribbean Coral Reefs

Abstract: Coral reefs provide a number of ecosystem services including coastal defense from storms, the generation of building materials, and fisheries. It is increasingly clear that the management of reef resources requires an ecosystem approach in which extractive activities are weighed against the needs of the ecosystem and its functions rather than solely those of the fishery. Here, I use a spatially explicit simulation model of a Caribbean coral reef to examine the ecosystem requirements for grazing which is primarily conducted by parrotfishes (Scaridae). The model allows the impact of fishing grazers to be assessed in the wider context of other ecosystem processes including coral–algal competition, hurricanes, and mass extinction of the herbivorous urchin Diadema antillarum. Using a new analytical model of scarid grazing, it is estimated that parrotfishes can only maintain between 10% and 30% of a structurally complex forereef in a grazed state. Predictions from this grazing model were then incorporated into a broader simulation model of the ecosystem. Simulations predict that scarid grazing is unable to maintain high levels of coral cover (≥30%) when severe hurricanes occur on a decadal basis, such as occurs in parts of the northern Caribbean. However, reefs can withstand such intense disturbance when grazing is undertaken by both scarids and the urchin Diadema. Scarid grazing is predicted to allow recovery from hurricanes when their incidence falls to 20 years or less (e.g., most of Central and South America). Sensitivity analyses revealed that scarid grazing had the most acute impact on model behavior, and depletion led to the emergence of a stable, algal-dominated community state. Under conditions of heavy grazer depletion, coral cover was predicted to decline rapidly from an initial level of 30% to less than 1% within 40 years, even when hurricane frequency was low at 60 years. Depleted grazers caused a population bottleneck in juvenile corals in which algal overgrowth caused elevated levels of postsettlement mortality and resulted in a bimodal distribution of coral sizes. Several new hypotheses were generated including a region-wide change in the spatial heterogeneity of coral reefs following extinction of Diadema. The management of parrotfishes on Caribbean reefs is usually approached implicitly through no-take marine reserves. The model predicts that depletion of grazers in nonreserve areas can severely limit coral accretion. Other studies have shown that low coral accretion can reduce the structural complexity and therefore quality of the reef habitat for many organisms. A speculative yet rational inference from the model is that failure to manage scarid populations outside reserves will have a profoundly negative impact on the functioning of the reserve system and status of non-reserve reefs.

Positive and negative effects of widespread badger culling on tuberculosis in cattle

Abstract: Human and livestock diseases can be difficult to control where infection persists in wildlife populations. For three decades, European badgers (Meles meles) have been culled by the British government in a series of attempts to limit the spread of Mycobacterium bovis, the causative agent of bovine tuberculosis (TB), to cattle. Despite these efforts, the incidence of TB in cattle has risen consistently, re-emerging as a primary concern for Britain's cattle industry. Recently, badger culling has attracted controversy because experimental studies have reached contrasting conclusions (albeit using different protocols), with culled areas showing either markedly reduced or increased incidence of TB in cattle. This has confused attempts to develop a science-based management policy. Here we use data from a large-scale, randomized field experiment to help resolve these apparent differences. We show that, as carried out in this experiment, culling reduces cattle TB incidence in the areas that are culled, but increases incidence in adjoining areas. These findings are biologically consistent with previous studies but will present challenges for policy development.

Leadership Competencies: Time to Change the Tune?

Abstract: This article indicates how the competency approach to leadership could be conceived of as a repeating refrain that continues to offer an illusory promise to rationalize and simplify the processes of selecting, measuring and developing leaders, yet only reflects a fragment of the complexity that is leadership. To make this argument we draw on two sets of data: a review of leadership competency frameworks and an analysis of participant reports from a reflective leadership development programme. A lexical analysis comparing the two data sets highlights a substantial difference with regards to the relative importance placed on the moral, emotional and relationship dimensions of leadership. The implications of these differences are considered, as are ways in which the competency approach could be aligned more closely with the current and future needs of leaders and organizations. In particular, we argue that a more discursive approach that helps to reveal and challenge underlying organizational assumptions is ...

Producing ultrastrong magnetic fields in neutron star mergers

Abstract: We report an extremely rapid mechanism for magnetic field amplification during the merger of a binary neutron star system. This has implications for the production of the short class of gamma-ray bursts, which recent observations suggest may originate in such mergers. In detailed magnetohydrodynamic simulations of the merger process, the fields are amplified by Kelvin-Helmholtz instabilities beyond magnetar field strength and may therefore represent the strongest magnetic fields in the universe. The amplification occurs in the shear layer that forms between the neutron stars and on a time scale of only 1 millisecond, that is, long before the remnant can collapse into a black hole.

Anger and Guilt About Ingroup Advantage Explain the Willingness for Political Action

Abstract: Three studies examined non-Aboriginal Australians’ guilt and anger about their ingroup’s advantage over structurally disadvantaged Aborigines. Study 1 showed that participants who perceived their ingroup as relatively advantaged perceived this inequality as unfair and felt guilt and anger about it. Anger, and to a lesser degree guilt, predicted the willingness to engage in political action regarding ingroup advantage. Study 2 showed both guilt and anger to be relatively self-focused because both were associated with appraising the ingroup’s (rather than the government’s) discrimination as responsible for ingroup advantage. Study 3 examined on participants especially willing to engage in political action to bring about systemic compensation to Aborigines. Anger about ingroup advantage was a potent predictor. Although guilt was associated with the abstract goal of systemic compensation, guilt did not explain willingness for political action. Results underline the importance of examining specific group-based emotions in intergroup relations.

Social identity in industrial and organizational psychology: concepts, controversies and contributions

Abstract: It is now 25 years since the publication of Tajfel and Turner’s (1979) seminal statement on social identity theory and 15 years since Ashforth and Mael (1989) published their classic Academy of Management Review article pointing to the potential value of using this theory to enhance researchers’ understanding of organizational life. Whatever else the latter article may have achieved, it is clear that it was highly prophetic, as, over the intervening period, industrial and organizational psychologists’ interest in social identity and related concepts has increased at a phenomenal rate. On top of nearly 300 citations of the Ashforth and Mael paper, this is indicated, among other developments, by the publication of several key books and journal special issues devoted to research in this area (e.g., Albert, Ashforth, & Dutton, 2000; Haslam, 2001, 2004; Haslam, van Knippenberg, Platow, & Ellemers, 2003; Hogg & Terry, 2001; Tyler & Blader, 2000; van Knippenberg & Hogg, 2001) and the exponential rise in articles that make reference to the terms ‘social’ and/or ‘organizational’ identity (for details see Haslam, 2004, p. xxv; Haslam, Postmes, & Ellemers, 2003). As the range of journals listed in Table 2.1 indicates, it is also apparent that this research has had a broad as well as a deep impact on the field. These trends indicate that a thoroughgoing review of the status of social identity in industrial and organizational fields is very timely (see also

Anxiety selectively disrupts visuospatial working memory.

Abstract: On the basis of a review of the extant literature describing emotion-cognition interactions, the authors propose 4 methodological desiderata for studying how task-irrelevant affect modulates cognition and present data from an experiment satisfying them. Consistent with accounts of the hemispheric asymmetries characterizing withdrawal-related negative affect and visuospatial working memory (WM) in prefrontal and parietal cortices, threat-induced anxiety selectively disrupted accuracy of spatial but not verbal WM performance. Furthermore, individual differences in physiological measures of anxiety statistically mediated the degree of disruption. A second experiment revealed that individuals characterized by high levels of behavioral inhibition exhibited more intense anxiety and relatively worse spatial WM performance in the absence of threat, solidifying the authors' inference that anxiety causally mediates disruption. These observations suggest a revision of extant models of how anxiety sculpts cognition and underscore the utility of the desiderata.

A symbolic data-driven technique based on evolutionary polynomial regression

Abstract: This paper describes a new hybrid regression method that combines the best features of conventional numerical regression techniques with the genetic programming symbolic regression technique. The key idea is to employ an evolutionary computing methodology to search for a model of the system/process being modelled and to employ parameter estimation to obtain constants using least squares. The new technique, termed Evolutionary Polynomial Regression (EPR) overcomes shortcomings in the GP process, such as computational performance; number of evolutionary parameters to tune and complexity of the symbolic models. Similarly, it alleviates issues arising from numerical regression, including difficulties in using physical insight and over-fitting problems. This paper demonstrates that EPR is good, both in interpolating data and in scientific knowledge discovery. As an illustration, EPR is used to identify polynomial formulae with progressively increasing levels of noise, to interpolate the Colebrook-White formula for a pipe resistance coefficient and to discover a formula for a resistance coefficient from experimental data.

Corporate Social Responsibility in Supply Chains of Global Brands: A Boundaryless Responsibility? Clarifications, Exceptions and Implications

Abstract: Corporate social responsibility (CSR) is increasingly becoming a popular business concept in developed economies. As typical of other business concepts, it is on its way to globalization through practices and structures of the globalized capitalist world order, typified in Multinational Corporations (MNCs). However, CSR often sits uncomfortably in this capitalist world order, as MNCs are often challenged by the global reach of their supply chains and the possible irresponsible practices inherent along these chains. The possibility of irresponsible practices puts global firms under pressure to protect their brands even if it means assuming responsibilities for the practices of their suppliers. Pressure groups understand this burden on firms and try to take advantage of the situation. This paper seeks to challenge the often taken-for-granted-assumption that firms should be accountable for the practices of their suppliers by espousing the moral (and sometimes legal) underpinnings of the concept of responsibility. Except where corporate control and or corporate grouping exist, it identifies the use of power as a critical factor to be considered in allocating responsibility in firm-supplier relationship; and suggests that the more powerful in this relationship has a responsibility to exert some moral influence on the weaker party. The paper highlights the use of code of conducts, corporate culture, anti-pressure group campaigns, personnel training and value reorientation as possible sources of wielding positive moral influence along supply chains.

The Physical Activity Patterns of European Youth with Reference to Methods of Assessment

Abstract: This article reviews the habitual physical activity of children and adolescents from member countries of the European Union in relation to methods of assessing and interpreting physical activity. Data are available from all European Union countries except Luxembourg and the trends are very similar. European boys of all ages participate in more physical activity than European girls and the gender difference is more marked when vigorous activity is considered. The physical activity levels of both genders are higher during childhood and decline as young people move through their teen years. Physical activity patterns are sporadic and sustained periods of moderate or vigorous physical activity are seldom achieved by many European children and adolescents. Expert committees have produced guidelines for health-related physical activity for youth but they are evidence-informed rather than evidence-based and where there is evidence of a relationship between physical activity during youth and health status there is little evidence of a particular shape of that relationship. The number of children who experience physical activity of the duration, frequency and intensity recommended by expert committees decreases with age but accurate estimates of how many girls and boys are inactive are clouded by methodological problems. If additional insights into the promotion of health through habitual physical activity during youth are to be made, methods of assessment need to be further refined and recommended guidelines re-visited in relation to the existing evidence base.

Gas Flow across Gaps in Protoplanetary Disks

Abstract: We analyze the gas accretion flow through a planet-produced gap in a protoplanetary disk. We adopt the α-disk model and ignore effects of planetary migration. We develop a semianalytic, one-dimensional model that accounts for the effects of the planet as a mass sink and also carry out two-dimensional hydrodynamic simulations of a planet embedded in a disk. The predictions of the mass flow rate through the gap based on the semianalytic model generally agree with the hydrodynamic simulations at the 25% level. Through these models, we are able to explore steady state disk structures and over large spatial ranges. The presence of an accreting ~1MJ planet significantly lowers the density of the disk within a region of several times the planet's orbital radius. The mass flow rate across the gap (and onto the central star) is typically 10%-25% of the mass accretion rate outside the orbit of the planet, for planet-to-star mass ratios that range from 5 × 10-5 to 1 × 10-3.