External Shaping Research Articles

On the conditions for up–down asymmetry in the core of tokamak equilibria: a matter of simple geometry

Drawing from decades-long-established results on tokamak equilibria (showing that flux surfaces closely surrounding the magnetic axis are ellipses), and using basic geometry and back-of-the-envelope calculations, recent theoretical results are revisited which have revealed that, for an externally imposed tilting, the elongation and hence the up–down asymmetry (UDA) of flux surfaces in the core of a tokamak plasma are inversely proportional to the toroidal current density flowing on axis. A figure of merit is also proposed to measure on-axis UDA, which stems from a simple geometrical analysis of elliptical flux surfaces and lies between zero and one. Moreover, it is shown that the current density on axis is bounded from below by the asymmetry-controlling coefficients themselves (which are essentially set by external shaping coils), meaning there is no way around it: enforcing stronger ellipticity from the outside can only result in increasing the minimum current density allowed in the core, whereas trying to make the latter go down is only possible with milder shaping coefficients. Such a severe structural constraint is simply the manifestation of a topological necessary condition to have closed flux surfaces nested around a tokamak magnetic axis and suggests that experimental attempts to push UDA from a strongly shaped plasma boundary into the core will remain mostly elusive.

Environmental Democratisation: Assessing the Impact of Democratisation on Environmental Capacity in South and Southeastern Europe

Although a relationship between established democratic political systems and environmental capacity has been described, the impact of the democratisation process on environmental capacity is not clear. The aim of this article is to determine the effect of both prior regime type and mode of transition on environmental capacity, through consideration of the cases of Bulgaria, Portugal, Romania and Spain. In addition, the importance of the European Union (EU) as an external actor shaping environmental capacity building is assessed. Findings indicate that variations in prior regime type and mode of transition had limited impact on environmental capacity development. Of greater importance were the persistent non-democratic legacies that influenced behaviours and actions during the democratisation period. The requirements of the EU were fundamental in ensuring that environmental issues remained on the domestic political agenda in such a context.

Quantification of dose perturbations induced by external and internal accessories in ocular proton therapy and evaluation of their dosimetric impact

Proton scattering on beam shaping devices and protons slowing down on media with different densities within the treatment volume may produce dose perturbations and range variations that are not predicted by treatment planning systems. The aim of this work was to assess the dosimetric impact of elements present in ocular proton therapy treatments that may disturb the prescribed treatment plan. Both distal beam shaping devices and intraocular elements were considered. A wedge filter, tantalum fiducial marker, hemispherical compensator, two intraocular endotamponades (densities 0.97 and 1.92 g cm(-3)) and an intraocular eye lens (IOL) were considered in the study. For these elements, longitudinal dose distributions were measured and∕or calculated in water in beam alignment for a clinical spread-out Bragg peak. Under the same conditions, the unperturbed dose distributions were similarly measured and∕or calculated in the absence of the element. The dosimetric impact was assessed by comparison of unperturbed and perturbed dose distributions. Measurements and calculations were carried out with two methods. Measurements are based on EBT3 films with dedicated software, which makes use of a calibration curve and correction for the quenching effect. Calculations are based on the Monte Carlo (MC) code MCNPX and reproduce the experimental conditions. Both dose maps are obtained with a resolution of 300 dpi. The degree of disturbance of distal beam shaping devices is low for the wedge filter (2% overdose ripple all along the central axis) and moderate for the hemispherical compensator (two bands of variable overdose of up to 10% downstream the compensator lateral edges and -5% underdose on the plateau at off-axis distance of 5 cm). Tantalum clips produce important dose shadows (-20% behind the clip parallel to the beam and range reduction of 1.1 mm) and bands of overdose (15%). The presence of endotamponades modifies the dose distribution very significantly (-5% underdose on the plateau and 3 mm range prolongation for the tamponade with density 0.97 g cm(-3) and -15% underdose on plateau and 8 mm range reduction for that with density 1.92 g cm(-3)). No dose perturbations were found for the IOL. The high performance of EBT3 film and MC tools used was confirmed and good agreement was found between them (percentage of pixels passing the gamma test >87%). The degree of disturbance by external beam shaping devices remains low in ocular proton therapy and can be reduced by bringing accessories closer to the eye. Tantalum fiducial markers must be located in such a way that dose perturbation is not projected on the tumor. The treatment of patients with intraocular endotamponades must be carefully managed. It is fundamental that radiation oncologists and medical physicists are informed about the presence of such substances prior to the treatment.

The Dynamics of China’s Accession to the WTO: Counting Sense, Coalitions and Constructs

AbstractThis article probes China’s admission to the World Trade Organization (WTO). China’s WTO accession deserves further analysis because much of the extant literature is divorced from the international relations (IR) literature. Moreover, while past analyses have considered external and internal factors shaping China’s stance towards joining the WTO, they have rarely gone beyond this to probing when particular variables mattered more. For its part, research that emphasises domestic factors falls short because it often treats such factors generically or fails to detail the path through which they affect issue identification, policy construction and implementation. This article addresses these lacunas by conducting a theoretically informed study of China’s WTO accession. While traditional interest-, power- and idea-based IR approaches to international governmental organisations (IGOs) capture various aspects of the story of China’s effort to join the WTO, they miss other critical features. This article argues that a leader-oriented cost-benefit model best explains China’s continued quest to become a WTO member, its aggressive pursuit of accession in the second half of the 1990s, and its willingness to tolerate very demanding WTO entry terms.

Mixed reproductive strategies of the Common moorhen on a microscale as revealed by genetic data

External factors shaping reproductive strategies within a population are still poorly understood. How individuals use space and where they decide to build a nest may influence reproductive strategies, as individuals that are close in space may more frequently interact socially. Here, we investigated a population (n=58 from 15 nests) of the Common moorhen in the Loir river (Western France) using microsatellite data (54 alleles). We found a surprisingly low level of genetic monogamy, a low relatedness among offspring in some nests and a low relatedness between the social parents and the offspring. Nest heterozygosity was highest close to the geographic center of the population. The mating strategies of the Common moorhen were highly variable, despite the social monogamy of the species, and were, to some extent, influenced by the microspatial structure. We discuss how our results contribute to the understanding of parent–offspring and offspring–offspring relationships.

A revised empirical model and CFD simulations for 3D axisymmetric steady-state flows of downbursts and impinging jets

It has been recognized that downburst wind accounts for a high proportion in annual extreme winds. Although real downburst wind characteristics are complicated and far from fully understood, simplified analytical and empirical models are useful tools in wind-resistant design of structures in areas where extreme winds are dominated by downbursts. This paper aims to establish a simple empirical model with improved accuracy for 3D axisymmetric steady-state velocity fields of downbursts and impinging jets. The original OBV model (Oseguera and Bowles, 1988; Vicroy, 1991) considers the boundary layer effects by shaping functions only and the development of boundary layer is regarded as a linear variation. However, the boundary layer thickness of downbursts and impinging jets grows nonlinearly. The revised model developed in this paper integrates the nonlinear effects by incorporating varying characteristic lengths into the velocity shaping functions and adds external shaping functions for intensity scalars. Besides, based on in-depth analysis of the intrinsic properties of the shaping functions, a simple vertical shaping function of radial velocity and a modification to radial shaping function of radial velocity are proposed to improve the simplicity and accuracy of the model. A detailed 3D CFD simulation study using Reynolds Stress Model (RSM) is performed for the fitting and verification of the revised model. Compared with the original OBV model, the revised model yields more accurate steady-state flow fields especially for radial velocity profiles.

Wideband 160-channel polyphase filter bank cable TV channeliser

The authors present a novel design of a wide bandwidth polyphase up-sampling filter bank formed by cascading external shaping filters, arbitrary interpolators and two stages of polyphase channelisation. The channeliser synthesises 160 channels with 6-MHz frequency centres and thus spans a two-sided baseband bandwidth of 960 MHz. The two stages of channelisation first form super channels from ten sets of 16-channels each in 32-path polyphase channelisers operating at an output sample rate of 192 MHz. These ten super channels are, in turn, channelised by a 16-path polyphase channeliser operating at an output sample rate of 1536 MHz. The two-stage approach permits the ten sets of first stage super channel channelisers to operate at an easy to implement medium sample rate. The complex baseband signal is further up-sampled 1-to-2 and translated to a digital intermediate frequency and pre-compensated for the sin(x)/x distortion of the output digital-to-analogue converter.

The Determinants Of European Bank Profitability

The rate of return earned by a financial institution is affected by numerous factors. These factors include elements internal to each financial institution and several important external forces shaping earnings performance. The type of explanation would determine possible policy implications and ought to be taken seriously. This paper reviews the literature on bank performance studies and classifies the bank profitability determinants. The second part of the paper quantifies how internal determinants (within effects changes) and external factors (dynamic reallocation effects) contribute to the performance of the EU banking industry as a whole in 1994-1998. We construct OLS and fixed effects models, and the results provide a new perspective for understanding the impact of changes in competition on the performance of the EU banking industry. The estimation results suggest that the profitability of European banks is influenced not only by factors related to their management decisions but also to changes in the external macroeconomic environment. The results are in contrast to studies that have examined the structure-performance relationship for European banking and find a positive effect of the concentration and/or market share variables on bank profitability.

Flat-top laser beam generated by coherent beam combining of Gaussian lasers

We present a flat-top laser beam generation scheme using coherent beam combining of hexagonally arranged Gaussian lasers. To produce a beam with a flat-top profile, we optimize the amplitude and phase of each unit laser using the least-square method. Simulation results show that with 13 unit lasers, a beam with the flatness of less than 1% in the optimizing region can be achieved. The main lobe contains over 95% of the total power. The scheme requires no external beam shaping element and has the potential to be designed for high-power applications.

Competitive Positioning and Continuity of Construction Firms in International Markets

In today’s global construction industry, firms exist in competitive market environments. To gain and maintain a competitive position in an increasingly challenging climate, firms must achieve a deep understanding of their dynamic environments and shape their strategies according to evolving conditions. Effectively leveraging external forces and shaping internal company focus in relation to the environment are essential for competitive positioning and achieving sustainable growth. This paper explores the concepts of competitive positioning and continuity in the context of mode (cost, quality, innovation, and timing) and scope (segment, vertical, geographic, and industry) of competition for U.S. and Turkish construction firms in international markets. The analysis of selected U.S. and Turkish firms demonstrates the strategic choice perspectives of different firms and the effects of environmental forces on these strategies over time. This study shows that construction firms tend to pursue consistent strategies in international markets while they adjust these strategies according to market demands and global tendencies. Research findings also show the differences between the strategic perspectives of construction firms in high and middle income countries enabling the identification of the factors for competitive advantage of nations in international construction markets.

Alternative Futures for Applied Sociology

The future of applied sociology is being shaped by a variety of factors including the historical development of the discipline, the institutional context of colleges and universities, and a wide variety of social trends related to the goals and funding of higher education. Five alternative scenarios for the future of applied sociology are set forth: “Down and Out,” “Subfield Status,” “Increasing Focus,” “Ascension of Applied Sociology,” and “Leaving Home.” Internal and external factors shaping contemporary higher education and their possible impacts on the future of applied sociology are considered in order to assess the likelihood of the five alternative futures.

Internal and external factors shaping educational beliefs of high school teachers of “sacred” subjects to girls

This research investigated pedagogical beliefs of teachers of “sacred” school subjects, curricular topics that the school community deems culturally valued, unassailable and inviolate. Two hundred and fifty-five teachers of girls only who taught sacred or secular subjects in Jewish modern religious high schools responded to questionnaires focusing on the discipline, on students and their learning and on the teacher role and 15 were interviewed. Results reflected systematic differences between teachers of sacred and secular subjects caused by multiple factors, some internal and some external to the underlying discipline. Variation among different sacred subjects was contingent mainly on external factors.

Bacterial body plans

The bacterium Serratia marcescens produces a plethora of multicellular shapes of different colorations on solid substrates, allowing immediate visual detection of varieties. Such a plasticity allows studies on multicellular community scale spanning two extremes, from well-elaborated individual colonies to undifferentiated cell mass.For a single strain and medium, we obtained a range of different multicellular bodies, depending on the layout of initial plating. Four principal factors affecting the morphogenetic pathways of such bodies can be distinguished: (1) amount, density, and distribution pattern of founder cells; (2) the configuration of surrounding free medium; (3) the presence and character of other bacterial bodies sharing the same niche; and (4) self-perception, resulting in delimitation towards other bodies. The last feature results in an ability of well-formed multicellular individuals to maintain their identity upon a close mutual contact, as well as in spontaneous separation of cell masses in experimental chimeras. We propose an "embryo-like" colony model where multicellular bacterial bodies develop along genuine ontogenetic pathways inherent to the given species (clone), while external shaping forces (like nutrient gradients, pH, etc.) exert not formative, but only regulative roles in the process.

Future trends in hepatology

Asa professional society, the American Association for the Study of Liver Diseases (AASLD) is an important instrument for coordinating and focusing the professional objectives of hepatology. As a prelude to an AASLD-sponsored strategic planning initiative, a Future Trends Meeting was convened on January 4-5, 2008. The focus was on the burden of liver disease, the current status of AASLD U.S. physician members, external forces shaping the profession, andmanpower/training paradigms. Despite enormous advances in the prevention, diagnosis, and therapy of patients with liver diseases, the burden of liver disease in the United States is substantial. There is an unmet public health need for professional expertise in liver diseases, which is not addressed by current training paradigms. New models of care are needed, funding challenges for sustaining hepatologists need to be addressed, and new training paradigms conceived and implemented. The information reviewed and emerging solutions developed to address the above challenges are reviewed herein. As a new AASLD strategic plan emerges to further refine the concepts developed at this meeting, it will be published in a separate document.

Demographic processes shaping genetic variation

Demographic processes modulate genome-wide levels and patterns of genetic variation via impacting effective population size independently of natural selection. Such processes include the perturbation of population distributions from external events shaping habitat landscape and internal factors shaping the probability of contemporaneous alleles in a population (coalescence). Several patterns have recently emerged: spatial and temporal heterogeneity in population structure have different influences on the persistence of new mutations and genetic variation, multi-locus analyses indicate that gene flow continues to occur during speciation and the incorporation of demographic processes into models of molecular evolution and association genetics approaches has improved statistical power to detect deviations from neutral-equilibrium expectations and decreased false positive rates.

Fatalism or Destiny? A Qualitative Study and Interpretative Framework on Dominican Women’s Breast Cancer Beliefs

A growing literature on Latino's beliefs about cancer focuses on the concept of fatalismo (fatalism), despite numerous conceptual ambiguities concerning its meaning, definition, and measurement. This study explored Latina women's views on breast cancer and screening within a cultural framework of destino ("destiny"), or the notion that both personal agency and external forces can influence health and life events. Semi-structured interviews were conducted with 25 Latinas from the Dominican Republic aged 40 or over. Respondents reported complex notions of health locus of control that encompassed both internal (e.g., individual action) and external (e.g., the will of God) forces shaping breast cancer prevention efforts. Furthermore, women actively participated in screening because they believed that cancer could become a death sentence if diagnosed late or left untreated. In contrast to simplistic notions of "fatalism", our analysis suggests complex strategies and beliefs regarding breast cancer and cancer screening that speak of resiliency rather than hopelessness.

Inductive sustainment of oblate field-reversed configurations with the assistance of magnetic diffusion, shaping, and finite-Larmor radius stabilization

Oblate field-reversed configurations (FRCs) have been sustained for >300μs, or >15 magnetic diffusion times, through the use of an inductive solenoid. These argon FRCs can have their poloidal flux sustained or increased, depending on the timing and strength of the induction. An inward pinch is observed during sustainment, leading to a peaking of the pressure profile and maintenance of the FRC equilibrium. The good stability observed in argon (and krypton) does not transfer to lighter gases, which develop terminal co-interchange instabilities. The stability in argon and krypton is attributed to a combination of external field shaping, magnetic diffusion, and finite-Larmor radius effects.

Karin Barber, ed. Africa's Hidden Histories: Everyday Literacy and Making the Self. Bloomington: Indiana University Press, 2006. ix + 451 pp. Illustrations. Photographs. Notes. References. Index. $75.00. Cloth. $29.95. Paper.

Karin Barber, ed. Africa's Hidden Histories: Everyday Literacy and Making the Self. Bloomington: Indiana University Press, 2006. ix + 451 pp. Illustrations. Photographs. Notes. References. Index. 29.95. Paper. - Volume 50 Issue 2

The World’s Bank and the Bank’s World

Abstract Who or what shapes and drives the policy and operational behavior of the World Bank? The objective of this essay is to lay the conceptual and empirical framework for this special issue. I begin by constructing a synthetic theoretical model—drawing from principal-agent models and sociological institutionalism—to delineate the set of external and internal factors shaping Bank behavior. I then lay the empirical groundwork by exploring the most salient characteristics of the “world's Bank,” taking special note of the Bank's relationship with the United States, borrowing states, and nongovernmental organizations. In the second half, I focus on the “Bank's world,” investigating the internal bureaucratic politics and culture of the Bank. Specifically, I examine the sources and nature of the Bank's “intellectual culture” (characterized by its economistic, apolitical, and technical rationality), its “operational culture” (portrayed as driven by approval and disbursement imperatives), and the dynamics of b...

Does organismal pedigree impact the magnitude of topological congruence among gene trees for unlinked loci?

One of the fundamental assumptions in the multi-locus approach to phylogeographic studies is that unlinked loci have independent genealogies. For this reason, congruence among gene trees from unlinked loci is normally interpreted as support for the existence of external forces that may have concordantly shaped the topology of multiple gene trees. However, it is also important to address and quantify the possibility that gene trees within a given species are all inherently constrained to some degree by their shared organismal pedigree, and thus in this strict sense are not entirely independent. Here we demonstrate by computer simulations that gene trees from a shared pedigree tend to display higher topological concordance than do gene trees from independent pedigrees with the same demographic parameters, but we also show that these constraining effects are normally minor in comparison to the much higher degree of topological concordance that can routinely emerge from external phylogeographic shaping forces. The topology-constraining effect of a shared pedigree decreases as effective population size increases, and becomes almost negligible in a random mating population of more than 1,000 individuals. Moreover, statistical detection of the pedigree effect requires a relatively large number of unlinked loci that far exceed what is typically used in current phylogeographic studies. Thus, with the possible exception of extremely small populations, multiple unlinked genes within a pedigree can indeed be assumed, for most practical purposes, to have independent genealogical histories.