bluuebunny/crossref_metadata_2025 huggingface dataset:
Abolishing the effect of reinforcement delay on human causal learning
Authors: Buehner Marc J. , May Jon
Published: March 2004

Associative learning theory postulates two main determinants for human causal learning: contingency and contiguity. In line with such an account, participants in Shanks, Pearson, and Dickinson (1989) failed to discover causal relations involving delays of more than two seconds. More recent research has shown that the impact of contiguity and delay is mediated by prior knowledge about the timeframe of the causal relation in question. Buehner and May (2002, 2003) demonstrated that the detrimental effect of delay can be significantly reduced if reasoners are aware of potential delays. Here we demonstrate for the first time that the negative influence of delay can be abolished completely by a subtle change in the experimental instructions. Temporal contiguity is thus not essential for human causal learning.
Should Soft Tissue Sarcomas be Treated at a Specialist Centre?
Authors: Bhangu A. A. , Beard J. A. S. , Grimer R. J.
Published: March 2004

Objective. We have investigated whether there is evidence that patients with soft tissue sarcomas do better if treated in a
specialist centre compared with district general hospitals.

Patients. All patients diagnosed with soft tissue sarcomas who were residents of WMRHA between 1994 and 1996, with
minimum follow up of 5 years, excluding head and neck or retroperitoneal tumors.

Methods. We reviewed data from the Royal Orthopaedic Hospital Oncology Service (ROHOS) database and the Cancer
Intelligence Unit (CIU) Database, with medial record review where necessary. Main outcome measures were local
recurrence and overall survival.

Results. A total of 260 patients were diagnosed as having STS over the 3‐year period (incidence=1.62per 100000 per
year): 37% of patients had the majority of treatment at the specialist centre under the care of three surgeons, whilst the other
63% were treated at a total of 38 different hospitals. The rate of local recurrence was 39% at the district general hospitals
compared with 19% at the specialist centre despite the fact that tumours treated at the district hospitals were smaller and of
lower grade. The most significant factors affecting survival were grade (high versus low) and depth of the tumour. Patients
treated at the specialist centre had a small survival advantage after multivariate testing.

Conclusion. Soft tissue sarcomas are rare. Centralization of treatment improves local control in all patients and survival in
some. Appropriate mechanisms for ensuring that patients with soft tissue sarcomas are seen and treated at specialist centres
should be developed.
The Anatomy of Sartorius Muscle and its Implications for Sarcoma Radiotherapy
Authors: Burnet Neil G. , Bennett-Britton Tom , Hoole Andrew C. F. , Jefferies Sarah J. , Parkin Ian G.
Published: March 2004

Purpose: Controversy exists as to whether sartorius muscle is completely invested in fascia. If it is, then direct tumour
involvement from soft tissue sarcoma of the anterior thigh would be unlikely and would justify omitting sartorius from the
radiotherapy volume.

Subjects and methods: Eight thighs in six cadavers were examined in the dissecting room. Using a previous case, conformal
radiotherapy plans were prepared to treat the anterior compartment of the thigh including and excluding sartorius. The
corridor of unirradiated normal tissue was outlined separately.

Results: In all cases, sartorius was enclosed within a fascial sheath of its own. In four of the six cadavers, there was clear
evidence of a fascial envelope surrounding sartorius, fused to the fascia lata and medial intermuscular septum. In two,
sartorius was fully ensheathed in the upper half of the thigh; in the lower half the intermuscular septum became
thin, and blended with the tendinous aponeurosis on the surface of vastus medialis in an example case. By excluding
sartorius, the volume of the anterior compartment was reduced by 8%, but the volume of the unirradiated normal tissue
corridor increased by 134%. With sartorius included, the unirradiated corridor became very small inferiorly, only 6% of the
circumference of the whole leg, compared to 27% with sartorius excluded.

Discussion: The anatomy suggests that sartorius could be safely omitted from the clinical target volume of anterior
compartment soft tissue sarcomas. This substantially increases the size of the unirradiated normal tissue corridor, expressed
as a volume and a circumference, which could give a clinical advantage by reducing normal tissue complications.
Adult Pelvic Sarcomas: A Heterogeneous Collection of Sarcomas?
Authors: Keyzer-Dekker Claudia M. G. , Houtkamp Richard G. , Peterse Johannes L. , Van Coevorden Frits
Published: March 2004

Introduction. Adult pelvic soft tissue sarcomas are a rare group of heterogeneous malignancies. These sarcomas differ from
extremity and trunk soft tissue sarcomas in presentation, characteristics and response to treatment.

Methods. A retrospective analysis of patient and tumor characteristics, treatment and prognosis and prognostic factors was
performed.

Results. Between 1977 and 1997, a total of 33 adult patients with soft tissue sarcomas involving the pelvis but excluding
uterine leiomyosarcoma were identified. Leiomyosarcomas (18), including six GIST, and rhabdomyosarcomas (eight) were
the most commonly seen tumors. At first presentation, nine patients already had metastases. The mean follow‐up was
52 months (1–200). Recurrences developed in 15 of the 24 cases (63%) with tumors without metastases at first presentation;
in six (25%) recurrence was locally only, in nine distant metastases occurred. The nine patients with metastatic disease
at first presentation died of the disease, while eight of the 24 patients with localized disease at presentation died. One patient
died of an unrelated cause, four were alive with disease, and 11 patients were alive and free of disease. The only identifiable
prognostic factor of disease‐free interval and overall survival was histological grade.

Conclusion. Soft tissue sarcomas of the pelvis appear to be associated with increased rate of metastasis at the time of diagnosis
and higher rates of local recurrence. In this study, multi‐modality treatment for most primary tumors did not show a
significant benefit in recurrence rate, DFI and OST, when compared to single modality approach. Although the number of
patients in this study is small, and different types of sarcomas were studied, the only identifiable predictor for survival was
low histological grade of the tumors. The differences of this heterogeneous group of pelvic sarcomas with retroperitoneal,
trunk and extremity sarcomas should be taken into consideration in the management of these sarcomas.
Diagnosis of High‐Grade Osteosarcoma by Radiology and Cytology: A Retrospective Study of 52 Cases
Authors: Söderlund Veli , Skoog Lambert , Unni Krishnan K. , Bertoni Franco , Brosjö Otte , Kreicbergs Andris
Published: March 2004

The diagnostic value of combined radiology and fine needle aspiration cytology (FNAC) was retrospectively assessed in
a consecutive series of 52 patients with high‐grade osteosarcoma. The series was divided into typical and atypical
osteosarcomas according to radiological features and site. Thirty‐two of 33 radiologically typical osteosarcoma cases were
correctly diagnosed by cytology; one lesion was diagnosed as sarcoma NOS. Nineteen osteosarcoma cases were
radiographically atypical. Six of these were diagnosed as osteosarcoma and another six as sarcoma NOS. In three cases
another type of sarcoma was suggested. One case was falsely classified as benign. FNAC of three cases were non‐diagnostic.
Overall, the diagnostic difficulties pertained to the radiologically atypical cases. Notably, four of these also posed
considerable difficulties in the histopathological assessment prompting external consultation. Our study suggests that open
biopsy can be obviated in high‐grade osteosarcomas exhibiting typical radiological features, i.e., in two‐thirds.
Discussion: A Defense of Bechtel and Mundale∗
Authors: Couch Mark B.
Published: March 2004

Kim claims that Bechtel and Mundale's case against multiple realization depends on the wrong kind of evidence. The latter argue that neuroscientific practice shows neural states across individuals and species are type identical. Kim replies that the evidence they cite to support this is irrelevant. I defend Bechtel and Mundale by showing why the evidence they cite is relevant and shows multiple realization does not occur.
Bayesianism and Unification: A Reply to Wayne Myrvold*
Authors: Lange Marc
Published: March 2004

Myrvold (2003) has proposed an attractive Bayesian account of why theories that unify phenomena tend to derive greater epistemic support from those phenomena than do theories that fail to unify them. It is argued, however, that “unification” in Myrvold's sense is both too easy and too difficult for theories to achieve. Myrvold's account fails to capture what it is that makes unification sometimes count in a theory's favor.
Different Gene Expression Patterns in Invasive Lobular and Ductal Carcinomas of the Breast
Authors: Zhao Hongjuan , Langerød Anita , Ji Youngran , Nowels Kent W. , Nesland Jahn M. , Tibshirani Rob , Bukholm Ida K. , Kåresen Rolf , Botstein David , Børresen-Dale Anne-Lise , Jeffrey Stefanie S.
Published: March 2004

Invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) are the two major histological types of breast cancer worldwide. Whereas IDC incidence has remained stable, ILC is the most rapidly increasing breast cancer phenotype in the United States and Western Europe. It is not clear whether IDC and ILC represent molecularly distinct entities and what genes might be involved in the development of these two phenotypes. We conducted comprehensive gene expression profiling studies to address these questions. Total RNA from 21 ILCs, 38 IDCs, two lymph node metastases, and three normal tissues were amplified and hybridized to ∼42,000 clone cDNA microarrays. Data were analyzed using hierarchical clustering algorithms and statistical analyses that identify differentially expressed genes (significance analysis of microarrays) and minimal subsets of genes (prediction analysis for microarrays) that succinctly distinguish ILCs and IDCs. Eleven of 21 (52%) of the ILCs (“typical” ILCs) clustered together and displayed different gene expression profiles from IDCs, whereas the other ILCs (“ductal-like” ILCs) were distributed between different IDC subtypes. Many of the differentially expressed genes between ILCs and IDCs code for proteins involved in cell adhesion/motility, lipid/fatty acid transport and metabolism, immune/defense response, and electron transport. Many genes that distinguish typical and ductal-like ILCs are involved in regulation of cell growth and immune response. Our data strongly suggest that over half the ILCs differ from IDCs not only in histological and clinical features but also in global transcription programs. The remaining ILCs closely resemble IDCs in their transcription patterns. Further studies are needed to explore the differences between ILC molecular subtypes and to determine whether they require different therapeutic strategies.
Local chromatin structure at the ribosomal DNA causes replication fork pausing and genome instability in the absence of the S. cerevisiae DNA helicase Rrm3p
Authors: Torres Jorge Z. , Bessler Jessica B. , Zakian Virginia A.
Published: March 2004

Lack of the yeast Rrm3p DNA helicase causes replication defects at multiple sites within ribosomal DNA (rDNA), includingat the replication fork barrier (RFB). These defects were unaltered in rrm3 sir2 cells. When the RFB binding Fob1p was deleted, rrm3-generated defects at the RFB were eliminated, but defects at other rDNA sites were not affected. Thus, specific protein–DNA complexes make replication Rrm3p-dependent. Because rrm3-induced increases in recombination and cell cycle length were only partially suppressed in rrm3 fob1 cells, which still required checkpoint and fork restart activities for viability, non-RFB rrm3-induced defects contribute to rDNA fragility and genome instability.
Leading the strategic development of intellectual capital
Authors: Herremans Irene M. , Isaac Robert G.
Published: March 2004

The Intellectual Capital Realization Process (ICRP), developed by the authors, permits the leaders of an organization to develop strategies to realize the potential of intellectual capital (IC). This process is consistent with the resource‐based view of the firm, which suggests looking inward to develop core competencies for building competitive advantages. By utilizing a public sector organization as an example, this paper seeks to inform the reader of the preliminary work and subsequent steps to follow when implementing the ICRP. The Canadian Sport Centre Calgary (CSCC) organization serves this purpose, although the ICRP has also proven equally successful when used in a private sector company. The ICRP helped the CSCC identify and plan the development of its unique capabilities, relationships, and processes that benefit the organization through the creation of leadership ability and the generation of wealth.
The implications of electronic B2B intermediaries for the buyer‐supplier interface
Authors: McIvor Ronan , Humphreys Paul
Published: March 2004

This paper examines the implications of electronic business‐to‐business intermediaries for the buyer‐supplier interface. Innovations in electronic commerce have a key role to play in managing inter‐organisational networks of supply chain members. The evidence presented in this paper illustrates that the Internet represents a powerful technology for commerce and communication at the buyer‐supplier interface. An overview is provided of the evolution of electronic commerce at the buyer‐supplier interface and the typical business models that have been developed. A theoretical framework is proposed, based on the inter‐organisational relationships paradigm. A number of case studies are presented which examine the role of electronic intermediaries at the buyer‐supplier interface. It is shown how the inter‐organisational relationships paradigm is an effective means of evaluating the buyer‐supplier interface in an electronic B2B environment. The application of the framework is discussed in relation to the three case studies and the implications for practitioners are highlighted.
Greening production: a South‐East Asian experience
Authors: Rao Purba
Published: March 2004

This paper studies the relevance of the “greening of production” in the South‐East Asian context. It investigates the various initiatives taken by the companies of this region and thereby identifies the factors that are critical in the process of greening production in this region. The significance of the factors are ascertained and validated through an empirical research that has been conducted across five countries of the region employing the structural equation‐modeling framework.
All‐pole equiripple approximations to arbitrary functions of frequency
Authors: Unsworth L.
Published: March 2004

The problem of determining a rational function whose magnitude characteristic approximates some arbitrary functions of frequency in an equiripple sense is discussed. A novel method that provides a rational all‐pole equiripple approximation to any arbitrary magnitude response in the frequency domain is described. The technique is applied to a typical example that serves to illustrate the effectiveness of the method.
Analytical modelling of an induction motor fed by a four‐switch PWM VSI
Authors: Klima Jiri
Published: March 2004

This paper presents analytical and experimental results that quantify the performance of an induction motor fed by a space‐vector pulse width modulated four‐switch (B4) voltage source inverter. First, as voltage vectors in the inverter form unsymmetrical sequences, the discrete Fourier transform is used to express the voltage vectors in symmetrical form. Second, by using a mixed p‐z approach for every voltage vector sequence, we can derive a closed‐form solution, including steady‐state and transient components of the motor currents. From the motor currents, we can derive an analytical equation for the electromagnetic torque. Both the steady‐state and transient components of the motor currents are determined in a simple and lucid analytical form, which avoids involved matrix inversion as well as exponentiation. The theoretical considerations are verified on an experimental unit.
Utilizing design sensitivity analysis for 3D optimization of transformer tank shields considering eddy currents
Authors: Yao Yingying , Seop Koh Chang , Seop Ryu Jae , Xie Dexin , Gun Um Tae
Published: March 2004

A novel 3D shape optimization algorithm is presented for electromagnetic devices carrying eddy current. The algorithm integrates the 3D finite element performance analysis and the steepest descent method with design sensitivity and mesh relocation method. For the design sensitivity formula, the adjoint variable vector is defined in complex form based on the 3D finite element method for eddy current problems. A new 3D mesh relocation method is also proposed using the deformation theory of the elastic body under stress to renew the mesh as the shape changes. The design sensitivity for the surface nodal points is also systematically converted into that for the design variables for the parameterized optimization application. The proposed algorithm is applied to the optimum design of the tank shield model of transformer and the effectiveness is proved.
Model reduction of nonlinear systems
Authors: Condon Marissa , Ivanov Rossen
Published: March 2004

This paper presents the application in circuit simulation of a method for model reduction of nonlinear systems that has recently been developed for chemical systems. The technique is an extension of the well‐known balanced truncation method that has been applied extensively in the reduction of linear systems. The technique involves the formation of controllability and observability gramians either by simulated results or by measurement data. The empirical gramians are subsequently employed to determine a subspace of the full state‐space that contains the most significant dynamics of the system. A Galerkin projection is used to project the system onto the subspace to form a lower‐dimensional nonlinear model. The method is applied to a nonlinear resistor network which is a standard example for exemplifying the effectiveness of a nonlinear reduction strategy.
Capacitances and singularities of the unit triangle, square, tetrahedron and cube
Authors: Read F.H.
Published: March 2004

The boundary element method has been used to obtain the electrical capacitances of the unit equilateral triangle, square, regular tetrahedron and cube. For each of these objects, a series of values of the number N of segments has been used and then empirical formulae have been used to extrapolate N to infinity. The singularities of the charge densities at the edges and corners of these objects can be characterised by power laws, the relevant exponents of which have also been determined.
A hybrid method for determining the reluctivity tensor components of Goss textured ferromagnetic materials
Authors: Vande Sande Hans , Henrotte François , Hameyer Kay , Froyen Ludo
Published: March 2004

For anisotropic materials, the magnetic field vector H→ and the flux density vector B→ are parallel with each other only along a few distinct directions. When performing unidirectional measurements, only the component of B→ along the direction under consideration is measured. It is not possible to deduce the angle between B→ and H→ from unidirectional measurements alone. For ferromagnetic materials having a Goss‐texture, as most transformer steels have, this paper demonstrates a way to compute this angle a posteriori, by the combination of measurements with a physical anisotropy model.
The relationship marketing process: communication, interaction, dialogue, value
Authors: Grönroos Christian
Published: March 2004

The objective of the article is to discuss a framework of central processes in relationship marketing. The framework includes an interaction process as the core, a planned communication process as the marketing communications support through distinct communications media, and a customer value process as the outcome of relationship marketing. If the interaction and planned communication processes are successfully integrated and geared towards customers' value processes, a relationship dialogue may merge.
Dialogue and its role in the development of relationship specific knowledge
Authors: Ballantyne David
Published: March 2004

In this article, dialogue is explored as an interactive process of learning together. This process is often spontaneous and unruly but bounded by a serious intent to reach mutual understanding. Also, the concept of relationship specific knowledge is introduced to explain how trust between business counterparts develops through dialogue in iterative cycles of learning. Dialogue also brings opportunities for generating new business knowledge, within the firm and between firms, in the form of creative solutions to marketing and supply problems. In this way, mutual value in buyer‐supplier exchanges is enhanced.
Investigation of forced convective heat transfer enhancement in the presence of an electric field – a finite element analysis
Authors: Bandyopadhyay Asish , Sen Swarnendu , Sarkar Amitava , Bhattacharyya Souvik
Published: March 2004

The effect of electro‐convection in a cylindrical flow annulus on heat transfer enhancement has been investigated numerically. Weakly ionized air is considered to be the working fluid throughout this work. The effect of exit boundary condition, considered to be the main hindrance for the numerical solution, has been discussed in detail. The present work shows interesting flow field characteristics, which are in excellent agreement with some other established experiments. The heat transfer enhancement, as reported in this work, appears to be small in view of the low magnitude of the applied voltage but it clearly and surely delineates the trend, i.e. with increase in the strength of the electric field, heat transfer enhances.
Forms of community participation and agencies’ role for the implementation of water‐induced disaster management: protecting and enhancing the poor
Authors: Osti Rabindra
Published: March 2004

Water‐induced hazards and disasters are usually compounded by the mismanagement of local water resources. Since the community bears the burden of disaster and is the first responder to the event, it is imperative to build the capacity of the community to enhance their coping mechanism and resilience to prepare for and face the disaster. The best strategy for the immediate as well as the long term cost‐benefit and pro‐environmental implications that will ensure prevention, mitigation and rehabilitation of water‐induced disaster is to ensure strong community participation. This paper elucidates the different forms of community participation and their comparative advantages in a socio‐economic dimension, thereby poverty alleviation. Agencies’ roles are analyzed in response to community participation. It is hoped that these theoretical and practical tips will benefit both community and agencies to work out better performances in advance.
Managing conflict between marketing and other functions within charitable organisations
Authors: Bennett Roger , Savani Sharmila
Published: March 2004

Extensive research has been undertaken into the proposition that certain organisational arrangements and working methods (e.g. centralisation, functional specialisation, multi‐disciplinary teamworking and training, organisation‐wide reward systems) influence the levels of dysfunctional conflict in businesses. The present study assessed the relevance of these variables for explaining the existence of conflict between marketing and other departments within non‐profit organisations. Additionally the investigation examined the role of “psychological distance” (a construct borrowed from the international marketing literature) as a possible determinant of conflict. A total of 148 marketing managers of large UK charities completed a questionnaire exploring these matters. It emerged that several of the factors known to mitigate dysfunctional conflict in the commercial world exerted similar effects in many of the sample charities. Psychological distance was significantly associated with both the presence of dysfunctional conflict within a charity and the manners whereby conflict resulted in adverse organisational consequences.
Managing the informal organisation: conceptual model
Authors: Morton S.C. , Brookes N.J. , Smart P.K. , Backhouse C.J. , Burns N.D.
Published: March 2004

Management thinking has seen organisations group product development activities in a number of ways in the quest to improve performance. The implementation of multi‐disciplinary teams has been recognised as a means of rapidly improving the way product development activities are managed. However, such an approach is not without its ills. Moreover, Henderson's research (Henderson, R., “Managing innovation in the information age”,Harvard Business Review, January, 1994, Reprint no. 94105) indicates that what governs product development success is the ability of the company to overcome the boundaries of any organisational grouping, rather than the type of organisation structure adopted. This research seeks to corroborate Henderson's propositions in a number of different industrial settings. Social network analysis helped embody the theory into a specification for a model to visualise and manipulate the informal organisation and the on‐going research activities further developed the specification into a working model that has been trialed in a number of different industrial settings. This paper sets the research context and presents the results thus far, both in the context of knowledge from academic research and practical application of the model. The working model has been able to manipulate the informal organisation by enabling visualisation of “core knowledge communities”, generating discussion, and supplying focus for individuals and teams to manage relationships more effectively and hence improve product development performance. Implications for further use of the model are reported, together with its potential for improving performance in organisational areas external to product development.
How process defines performance management
Authors: Wilson Andrew
Published: March 2004

This paper is based on a real life example of a department in a county council in the UK in 2002. The paper uses this simple example to raise generic issues of process definition and performance measurement. It then uses these issues to clarify the challenges in implementing a balanced business scorecard.
From simple rules to cycling in community assembly
Authors: Schreiber Sebastian J. , Rittenhouse Seth
Published: March 2004

Simulation studies of community assembly have frequently observed two related phenomena: (1) the humpty dumpty effect in which communities can not be reconstructed by “sequential” invasions (i.e. single species invasions separated by long intervals of time) and (2) cycling between sub‐communities. To better understand the mechanisms underlying these phenomena, we analyze a system consisting of two predators and two prey competing for a shared resource. We show how simple dominance rules (i.e. R* and P* rules) lead to cycling between sub‐communities consisting of predator–prey pairs; predator and prey invasions alternatively lead to prey displacement via apparent competition and predator displacement via exploitative competition. We also show that these cycles are often dynamically unstable in the population phase space. More specifically, while for too slow invasion rates (i.e. “sequential” invasions) the system cycles indefinitely, faster invasion rates lead to coexistence of all species. In the later case, the assembly dynamics exhibit transient cycling between predator‐prey subcommunities and the length of these transients decreases with the invasion rate and increases with habitat productivity.
Importance of Silene latifolia ssp. alba and S. dioica (Caryophyllaceae) as host plants of the parasitic pollinator Hadena bicruris (Lepidoptera, Noctuidae)
Authors: Bopp Sigrun , Gottsberger Gerhard
Published: March 2004

With regards to pollination there exist several mutualistic relationships between Hadena‐species and Caryophyllaceae. As mutualists have both negative and positive effects on their partners, mutualism is often betoken as reciprocative exploitation which may shift to parasitism if the exploitation of one partner becomes prevalent.

Several Silene‐ and Saponaria‐species are considered to be larval host plants of Hadena bicruris. Although Silene latifolia ssp. alba and S. dioica are frequently cited as hosts of the seed eating larvae, field and laboratory observations at Ulm were suggestive for only S. latifolia ssp. alba being a suitable host. Records of the oviposition behavior of H. bicruris made it evident that in fact a considerable number of eggs could be found in planted stands of both species. On the other hand, phenological data of the flowering periods and of the oviposition behavior of H. bicruris showed that S. latifolia ssp. alba is clearly preferred for oviposition if host selection is possible due to contemporaneous flowering of individuals of both plant species growing at close range. In addition, the flowering periods of S. latifolia ssp. alba and the periods of moth activity overlap to a large extent. This is not the case in S. dioica. Feeding experiences first indicated that the caterpillars may not prefer one of the species to the other, but comparison of the pupal weight of the animals reared on fruits of exclusively one of the species showed that the seeds of S. latifolia ssp. alba were more profitable for nutrition than those of S. dioica; the pupal weight of animals reared on seeds of the former species significantly exceeded that of animals reared on seeds of the latter one. The question arises if the symbiosis of H. bicruris and its hosts constitutes a stable situation or if an evolutionary shift to mutualism or parasitism will take place.
Patch dynamics in a landscape modified by ecosystem engineers
Authors: Wright Justin P. , Gurney William S. C. , Jones Clive G.
Published: March 2004

Ecosystem engineers, organisms that modify the environment, have the potential to dramatically alter ecosystem structure and function at large spatial scales. The degree to which ecosystem engineering produces large‐scale effects is, in part, dependent on the dynamics of the patches that engineers create. Here we develop a set of models that links the population dynamics of ecosystem engineers to the dynamics of the patches that they create. We show that the relative abundance of different patch types in an engineered landscape is dependent upon the production of successful colonists from engineered patches and the rate at which critical resources are depleted by engineers and then renewed. We also consider the effects of immigration from either outside the system or from engineers that are present in non‐engineered patches, and the effects of engineers that can recolonize patches before they are fully recovered on the steady state distribution of different patch types. We use data collected on the population dynamics of a model engineer, the beaver, to estimate the per‐patch production rate of new colonists, the decay rate of engineered patches, and the recovery rate of abandoned patches. We use these estimated parameters as a baseline to determine the effects of varying parameters on the distribution of different patch types. We suggest a number of hypotheses that derive from model predictions and that could serve as tests of the model.
Species richness of moss landscapes unaffected by short‐term fragmentation
Authors: Hoyle Martin , Gilbert Francis
Published: March 2004

Theory predicts that habitat fragmentation and varying corridor length and width will affect animal populations in adjoining habitat patches due to varying migration rates. Previous work on the moss/microarthropod microcosm showed that connecting moss patches with moss corridors maintained species richness and individual species abundance. By contrast, in this study there was little evidence for differences in species richness between landscapes of varying connectivity and corridor length and width. The γ diversity, the cumulative species richness of entire connected systems, followed the same pattern. Similar non‐significant results were obtained for species abundance. Contrary to a previous study, I found no evidence that populations of predators were more affected by fragmentation than non‐predators. Since this experiment ran during temperate environmental conditions and the previous experiments ran during more extreme conditions, I hypothesise that corridors may be more useful in reducing species extinction during extreme environmental conditions.
Dual role of harvesting ants as seed predators and dispersers of a non‐myrmechorous Mediterranean perennial herb
Authors: Retana Javier , Xavier Picó F. , Rodrigo Anselm
Published: March 2004

Ants have been traditionally considered either as predators or dispersers of seeds, but not both. That is, ant dispersal is restricted to myrmecochorous seeds, while almost all seeds removed by seed‐harvesting ants are eaten. However, harvesting ants might be simultaneously antagonistic and mutualistic towards seeds. This study analyzes the predation–dispersal relationship between seed‐harvesting ants and seeds ofLobularia maritima, a non‐myrmechorous perennial herb, in order to disentangle the dual role of ants as dispersers and predators ofL. maritimaseeds. The results obtained confirm the role of harvesting ants as both predators and dispersers of the non‐myrmechorous seeds ofL. maritima. The removal activity ofMessor bouvierionL. maritimaseeds is very important, particularly in autumn, which is the flowering and fruiting peak of this plant. It can be estimated that harvesting ants collect more than 85% of seeds, and almost 70% of them are effectively lost to predation. However, these granivorous ants also have drawbacks as seed dispersers. There is a relatively small percent of seeds collected by ants that escape predation, either because they are dropped on the way to the nest (16.4% of seeds harvested), or because they are mistakenly rejected on the refuse pile (0.9%). Abiotic dispersal ofL. maritimaseeds in the absence of ants occurs over very short distances from the plant stem. As seeds dispersed by ants reach a considerably greater distance than that obtained by gravity, this might represent a real advantage for the species, because it reduces intraspecific adult competition for seedlings, which directly influences seedling survivorship. These results challenge the generalization that seed removal by ants generally leads to successful seed dispersal if done by legitimate seed dispersers, or seed loss if done by seed consumers that eat them, and confirm that harvesting ants might have a dual role as both predators and dispersers of nonmyrmechorous seeds.
Estimating the richness of species with variable mobility
Authors: Brose Ulrich , D. Martinez Neo
Published: March 2004

The vast majority of species are animals that, unlike most plants and fungi, are variably and often highly mobile. While species’ mobility affects species’ probabilities of being sampled, effects of movement on the estimation of species richness have yet to be systematically investigated. Information‐rich abundance‐based estimators may be able to address variably mobile species but the accuracy of these estimators has also yet to be investigated. Here, we address both issues by variably sampling simulated landscapes with up to 250 species and evaluating the performance of ten non‐parametric estimators and one species accumulation curve. Our results show that some abundance‐based estimators are as accurate as better known and tested incidence‐based estimators. Increased movement heterogeneity between the species reduced estimator performance by reducing the sample coverage, which systematically determined which estimator was most accurate. Based on these findings, we present the first decision framework for choosing the most accurate of many available abundance‐based species‐richness estimators. These decisions, based on data coverage, can significantly improve investigators’ ability to estimate faunal species richness.
Sexual size dimorphism in northern giant petrels: ecological correlates and scaling
Authors: González‐Solís Jacob
Published: March 2004

Northern giant petrels (Macronectes halli) are among the largest and most sexually size dimorphic species of seabirds, with females being only 80% the mass of males. Both sexes scavenge on seal and penguin carrion in the sub‐Antarctic ecosystem, but during the breeding season females also feed extensively on other marine food resources and show more pelagic habits than males. The outstanding sexual segregation in foraging and feeding ecology in northern giant petrels suggests that mechanisms maintaining sexual size dimorphism by ecological factors may be operating. I evaluated this possibility by examining ecological correlates with body size and by static allometry analyses. Fledging sex ratio in four consecutive years did not depart from parity. There was no assortative mating by size neither association between the male size with the breeding performance. By contrast, smaller females raised their chick in better condition. Moreover, bill size showed a size dimorphism beyond that expected by body size dimorphism, i.e. when controlling for body mass, males showed relatively longer bill than females. This trait did not deviate from isometry with respect to body size and its phenotypic variability was low, suggesting that the disproportionately large bill of males is related to their more scavenging life style compared to females. In general, the increase and maintenance of sexual size dimorphism in giant petrels is more consistent with an ecological causation rather than a result of sexual selection.
Physiological and reproductive differences between hermaphrodites and males in the androdioecious plant Fraxinus ornus
Authors: Verdú Miguel
Published: March 2004

Androdioecy, the co‐occurrence of males and hermaphrodites in a breeding population, is a rare reproductive system in the nature. This rarity may be the result of the large fitness gain required for male plants to be maintained by selection. Physiological, vegetative and reproductive characters of males and hermaphrodites of the androdioecious species Fraxinus ornus (Oleaceae) were compared, supporting the hypothesis that males compensate the fitness advantage of hermaphrodites with greater reproductive ‐but not vegetative‐ output, with concomitant differences in physiological capacities between the genders. Photosynthetic rate was similar between both genders, but hermaphrodites had lower water potential and carbon isotope discrimination than males. Photosynthesis rates decreased with decreasing water potentials more steeply in males than in hermaphrodites, indicating that hermaphrodites were more drought tolerant than males. Vegetative characters such as current year shoot growth or tree size did not differ between genders. Males produced 1.6 times more inflorescences than hermaphrodites. This difference was consistent across years and populations.
Making eggs from nectar: the role of life history and dietary carbon turnover in butterfly reproductive resource allocation
Authors: O'Brien Diane M. , Boggs Carol L. , Fogel Marilyn L.
Published: March 2004

The diets of many butterflies and moths change dramatically with development: from herbivory in the larvae to nectarivory in the adults. These diets are nutritionally distinct, and thus are likely to contribute differentially to egg manufacture. We examine the use of dietary resources in egg manufacture by four butterfly species with different patterns of oviposition and lifespan; three in the Nymphalidae (Euphydryas chalcedona, Speyeria mormonia and Heliconius charitonia), and one in the Pieridae (Colias eurytheme). Each species was fed two isotopically distinct adult diets based on sucrose, both of which differed from the larval hostplant in 13C content. Egg isotopic composition was analyzed to quantify the contribution of carbon from the larval and adult diets to egg manufacture. In all four species, egg 13C content increased to an asymptotic maximum with time, indicating that adult diet is an increasingly important source of egg carbon . The 13C increase closely resembled that of a nectar‐feeding hawkmoth, and was well‐described by a model of carbon flow proposed for that species. This similarity suggests that the turnover from larval to adult dietary support of egg manufacture is conserved among nectar‐feeding Lepidoptera. Species varied widely in the maximum % egg carbon that derives from the adult diet, from 44% in E. chalcedona to nearly 80% in S. mormonia. These differences were related both to the extent of oocyte provisioning prior to adult emergence, and to egg composition. A species’ lifetime use of larval vs adult resources in egg manufacture reflected both the carbon turnover of the eggs and the timing of oviposition. Thus, the extent to which dietary resources are important in egg manufacture in butterflies depends on development (egg provisioning in teneral adults), behavior (timing of oviposition) and nutritional physiology (nutrient synthesis and turnover).
Identification of suitable unoccupied habitats in metapopulation studies using co‐occurrence of species
Authors: Münzbergová Zuzana , Herben Tomáš
Published: March 2004

This study proposed a new quantitative technique to identify suitable but unoccupied habitats for metapopulation studies in plants. It is based on species composition at the habitat and knowledge of species co‐occurrence patterns. It uses data from a large phytosociological database as a background for estimating species co‐occurrence patterns. If such a database is not available, the technique can still be applied using the same data for which the prediction is done to estimate the species co‐occurrence pattern. Using the technique we were able to indicate suitable unoccupied habitats and differentiate them from the unoccupied unsuitable ones. We also identified habitats with low probability of being suitable that were occupied. Compared to a direct approach of identification of suitable habitats, which involves introduction of a species to the habitat and studying its performance, the approach presented here is much easier to apply and can provide extensive information on habitat suitability for a range of species with much less effort and time needed.
Are long penis bones an adaption to high latitude snowy environments?
Authors: H. Ferguson Steven , Larivière Serge
Published: March 2004

Animals adapted to high latitude environments typically live at relatively low densities and require large areas to acquire the requisites for successful reproduction. Also, the unpredictable distribution of energy across time and space, such as environmental seasonality, constrains the timing of mating and parturition and imposes limitations to reproductive strategies. For example, limited mobility due to snow accumulation may reduce mate encounters, and this selective pressure may have resulted in morphological adaptations to assess mate quality during serial encounters. We tested whether mammalian carnivores living in high latitude environments displayed greater use of copulatory competition via length of the penis bone or baculum, and whether females in such settings enhance competition among males via multi‐male matings. We then examined how baculum length may correlate with other reproductive adaptations in high latitude environments such as delayed implantation and induced ovulation. Statistical methods that account for phylogeny revealed that longer bacula occur in carnivores living in high latitude environments with greater snow accumulation, and that larger bacula is also associated with delayed implantation and multi‐male mating systems. In contrast, the smallest bacula were observed in polygynous species. Our results provide an example of the effects of ecology on the evolution of a secondary sexual character due to sexual selection. Selection pressures imposed by seasonality of resources and environmental conditions affecting locomotion may have led to sexual selection via mating systems for females, and counter morphological adaptations of long penis bones in males.
Fundamental Theorems of Asset Pricing for Good Deal Bounds
Authors: Staum Jeremy
Published: March 2004

We prove fundamental theorems of asset pricing for good deal bounds in incomplete markets. These theorems relate arbitrage‐freedom and uniqueness of prices for over‐the‐counter derivatives to existence and uniqueness of a pricing kernel that is consistent with market prices and the acceptance set of good deals. They are proved using duality of convex optimization in locally convex linear topological spaces. The concepts investigated are closely related to convex and coherent risk measures, exact functionals, and coherent lower previsions in the theory of imprecise probabilities.
Pareto Equilibria with coherent measures of risk
Authors: Heath David , Ku Hyejin
Published: March 2004

In this paper, we provide a definition of Pareto equilibrium in terms of risk measures, and present necessary and sufficient conditions for equilibrium in a market with finitely many traders (whom we call “banks”) who trade with each other in a financial market. Each bank has a preference relation on random payoffs which is monotonic, complete, transitive, convex, and continuous; we show that this, together with the current position of the bank, leads to a family of valuation measures for the bank. We show that a market is in Pareto equilibrium if and only if there exists a (possibly signed) measure that, for each bank, agrees with a positive convex combination of all valuation measures used by that bank on securities traded by that bank.
Structural features of Escherichia coli heat‐stable enterotoxin that activates membrane‐associated guanylyl cyclase
Authors: Sato T. , Shimonishi Y.
Published: March 2004

Abstract:  Heat‐stable enterotoxin (ST), a small peptide of 18 or 19 amino acid residues produced by enterotoxigenic Escherichia coli, is the cause of acute diarrhea in infants and travelers in developing countries. ST triggers a biological response by binding to a membrane‐associated guanylyl cyclase C (GC‐C) which is located on intestinal epithelial cell membranes. This binding causes an increase in the concentration of cGMP as a second messenger in cells and activates protein kinase A and cystic fibrosis transmembrane conductance regulator. Here we describe the crystal structure of an ST at 0.89 Å resolution. The molecule has a ring‐shaped molecular architecture consisting of six peptide molecules with external and internal diameters of approximately 35 and 7 Å, respectively and a thickness of approximately 11 Å. The conserved residues at the central portion of ST are distributed on the outer surface of the ring‐shaped peptide hexamer, suggesting that the hexamer may be implicated in the association with GC‐C through these invariant residues.