bluuebunny/crossref_metadata_2025 huggingface dataset:
An improved CML estimation procedure for the Rasch model with item response data
Authors: Sheng Xiaoming , Carrière K. C.
Published: August 2002

Ordinal response data are commonly observed in health and medical investigations that include several items. The primary goal in the modelling of item response data is to find a unique measurement of the person's abilities and of the item difficulties that satisfies the properties of the fundamental measurement. One such analytic method in item response theory is the Rasch measurement, which is a way to convert ordinal observations into linear measures. Current estimation strategies assume the independence of the Rasch model parameters. In this paper, based on the conditional maximum likelihood, we implemented a simultaneous estimation method that can compare the Rasch parameters more efficiently. We also obtained the asymptotic properties of these estimators and developed the conditional likelihood ratio test for the goodness‐of‐fit of the model. Simulation studies were used to demonstrate the improved performance of our estimators as compared to that of currently used conditional method known as the CON procedure. We conclude that our estimation method outperforms CON in both model fit and the precision of the Rasch estimators. Copyright © 2002 John Wiley & Sons, Ltd.
Detecting and eliminating erroneous gestational ages: a normal mixture model
Authors: Platt Robert W. , Abrahamowicz Michal , Kramer Michael S. , Joseph K. S. , Mery Les , Blondel Béatrice , Bréart Gérard , Wen S. W.
Published: August 2002

In perinatal research and clinical practice, gestational age is a crucial variable for measuring foetal ‘growth’ (birth weight for gestational age) and for estimating the risk of mortality and morbidity, yet reported gestational age values are affected by random and systematic errors due to the absence of a gold standard measure. Previous investigators have used birth weight (which is measured with greater validity and precision than is gestational age) to correct such errors, but existing methods are inadequate due to unreasonable assumptions about the distributions of birth weight and gestational age. We propose a new method for identifying and correcting implausible observations using the expectation‐maximization (EM) algorithm. Using population‐based data from U.S. birth certificates, we compare the resulting gestational ages, birth weight distributions at each gestational age, and gestational age‐specific infant mortality based on the new method with those on the same population produced by previous published correction methods. The new method gives the best birth weight distributions for gestational age and the most realistic gestational‐age‐specific mortality rates, while each of the other methods has at least one significant flaw. Copyright © 2001 John Wiley & Sons, Ltd.
Statistical issues in bioequivalance
Authors: Senn Stephen
Published: August 2002

There has been much work recently on individual bioequivalence and the topic has attracted considerable controversy. Some previous controversies regarding average bioequivalence are examined. It is argued that a contributory factor in these controversies may have been confusion over the purpose of bioequivalence trials. It is concluded that this purpose needs further clarification before guidelines for individual bioequivalence can be established and indeed that such guidelines may turn out to be unnecessary. Copyright © 2001 John Wiley & Sons, Ltd.
Value creation in E‐business
Authors: Amit Raphael , Zott Christoph
Published: August 2002

We explore the theoretical foundations of value creation in e‐business by examining how 59 American and European e‐businesses that have recently become publicly traded corporations create value. We observe that in e‐business new value can be created by the ways in which transactions are enabled. Grounded in the rich data obtained from case study analyses and in the received theory in entrepreneurship and strategic management, we develop a model of the sources of value creation. The model suggests that the value creation potential of e‐businesses hinges on four interdependent dimensions, namely: efficiency, complementarities, lock‐in, and novelty. Our findings suggest that no single entrepreneurship or strategic management theory can fully explain the value creation potential of e‐business. Rather, an integration of the received theoretical perspectives on value creation is needed. To enable such an integration, we offer the business model construct as a unit of analysis for future research on value creation in e‐business. A business model depicts the design of transaction content, structure, and governance so as to create value through the exploitation of business opportunities. We propose that a firm's business model is an important locus of innovation and a crucial source of value creation for the firm and its suppliers, partners, and customers. Copyright © 2001 John Wiley & Sons, Ltd.
The structure of ownership and corporate acquisition strategies
Authors: Wright Peter , Kroll Mark , Lado Augustine , Van Ness Bonnie
Published: August 2002

In this study, we examine in an agency‐theoretic context the influence of executive equity stakes upon corporate strategy and firm value. We argue that beneficial, risk‐increasing corporate strategies may initially be emphasized but non‐value‐maximizing, risk‐reducing strategies may subsequently be emphasized as managers expand their stock ownership. We alternatively contend that stock options may have a consistently positive impact on firm risk taking and acquisition returns. The empirical findings are supportive of our expectations. Copyright © 2002 John Wiley & Sons, Ltd.
The persistence of knowledge‐based advantage: an empirical test for product performance and technological knowledge
Authors: McEvily Susan K. , Chakravarthy Bala
Published: August 2002

Resource‐based theory maintains that intrinsic characteristics of resources and capabilities, such as their tacitness, complexity, and specificity, prevent imitation and thereby prolong exceptional performance. There is little direct evidence to verify these claims, yet a substantial literature encourages firms to formulate competitive strategies around resources with these attributes. Further, work outside the resource‐based tradition suggests that these attributes can slow innovation, and it is not clear when this effect outweighs the benefits of inimitability. This paper seeks to clarify whether and how the complexity, tacitness, and specificity of a firm's knowledge affect the persistence of its performance advantages. We find that the complexity and tacitness of technological knowledge are useful for defending a firm's major product improvements from imitation, but not for protecting its minor improvements. The design specificity of technological knowledge delayed imitation of minor improvements in this study. Copyright © 2002 John Wiley & Sons, Ltd.
Value creation in fine arts: a system dynamics model of inverse demand and information cascades
Authors: Crossland Philip , Smith faye l.
Published: August 2002

We integrate information cascades and demand queue behaviors as they affect the distribution of marginal value added in the value chain. We develop a system dynamics model of the relationships of Edward Marshall Boehm, Inc., a studio that creates hard‐paste porcelain pieces of fine art sculpture. The relationships between information cascades, demand queues, and the distribution of marginal value added are applicable to other fine art settings and other industries. Copyright © 2002 John Wiley & Sons, Ltd.
Taking Syntegrity‐4 from assumption mode to reflection mode
Authors: Holmberg Stig C.
Published: August 2002

A model, Syntegrity‐4, for competence development in small and medium‐seized enterprises (SMEs) is designed. Syntegrity‐4 builds on the assumptions that competence development is a continuous activity that is best undertaken in a network with cooperation between different types of actors. Further, it is presumed that systemics and informatics have much to provide in increasing the skills of individual workers as well as the workforce as a whole. In working with the employees in a number of enterprises those assumptions have at large proven to be correct. However, the methodology in its present form is not good enough. No drastic and long‐lasting positive effects could be observed in the cooperating enterprises. Hence, a group of further steps for improving and complementing Syntegrity‐4 are identified. Copyright © 2001 John Wiley & Sons, Ltd.
The forgotten revenue of product development: learning new competence
Authors: Österlund Jan
Published: August 2002

The result of a new product development (NPD) process is not only a new product of desired quality but also learning new competence from problem‐solving experience. The learning results in a core competence, unique to the company, that makes it competitive in the future. Research results show that groups of specialists develop core competencies through learning by experience from joint problem solving at the technological front line. Specialists in a particular field, talking the same professional language, act as a living system in a self‐organizing group. Primarily individuals make experiences as tacit knowledge. It is then confirmed in a dialogue with colleagues in the specialist group to which the individual belongs. However, providing competence resources to high‐technology projects of a complex nature requires cross‐disciplinary teamwork. Therefore the knowledge from experience has to be transferred to a form that the entire organization can comprehend. This requires a creative learning process of innovating new concepts that all organization members concerned understand and find useful. To be successful, such a learning process must rely on a culture supporting it by an atmosphere of openness and innovativeness. It is therefore a managerial task to foster a supporting culture by giving suitable information to all levels of the company. Copyright © 2001 John Wiley & Sons, Ltd.
Creative distortions and social improvements
Authors: Soudijn Karel
Published: August 2002

Research in the field of psychotherapy is dominated by a medical metaphor, giving rise to standardized procedures which restrict interaction between therapist and client in a way that may often be deemed as counter‐productive. Conversations with Gerard de Zeeuw suggested alternative procedures for gathering information to enhance the development of psychotherapeutic interventions. This approach to research may be labelled as a kind of interactional perspectivism. The paper itself may be read as a personal reflection on de Zeeuw's teachings about developing a more social view on improvement. Copyright © 2002 John Wiley & Sons, Ltd.
Pathologic analysis of sentinel lymph nodes
Authors: van Diest Paul J. , Torrenga Hans , Meijer Sybren , Meijer Chris J.L.M.
Published: August 2002

The sentinel lymph node (SLN) procedure enables selective targeting of the first draining lymph node, where the initial metastases will form. A negative SLN predicts the absence of tumor metastases in the other regional lymph nodes with a high degree of accuracy. This means that in case of a negative SLN, regional lymph node dissection is no longer necessary. Besides saving patients the significant morbidity associated with lymph node dissection, it will also save costs.

Crucial for the success of the SLN procedure is the screening of the SLN for metastases by the pathologist. To this end, several techniques are available such as standard histo‐ and cytopathological techniques, immunohistochemistry, flow cytometry, and molecular biological techniques. In this paper, the value of these methods for detecting SLN metastases is discussed. Some of these techniques have also appeared to be quite useful for intraoperative evaluation of SLNs.

The standard protocol for detection of SLN metastases consists of extensive histopathological investigation including stepped sections stained with hematoxylin and eosin (HE) and immunohistochemistry. Intraoperative frozen section analysis and imprint cytology of SLNs have been shown to be reasonably reliable for detecting breast cancer metastases in SLNs. Further studies are necessary to establish the role of multiparameter flow cytometry and sophisticated molecular biological techniques such as reverse transcription polymerase chain reaction (RT‐PCR) in detecting SLN metastases. Semin. Surg. Oncol. 20:238–245, 2001. © 2001 Wiley‐Liss, Inc.
An active tendon control scheme for cable‐stayed bridges with model uncertainties and seismic excitation
Authors: Rodellar J. , Mañosa V. , Monroy C.
Published: August 2002

This paper proposes an active scheme for vibration control of cable‐stayed bridges under seismic loads. The control action is supplied by using a subset of the stay cables as active tendons. The dynamic model of the bridge is decomposed into two coupled subsystems, one of them including the degrees of freedom that are directly influenced by the active tendons. A linear control law is proposed to drive the active tendons via feedback of the states of these degrees of freedom only. A stability analysis gives conditions to ensure the existence of a ball of ultimate boundedness for the whole bridge model in the presence of a class of uncertainties in the model parameters and the seismic excitation. The effectiveness of the control scheme is shown numerically on a finite element model of a pedestrian cable‐stayed bridge Copyright © 2002 John Wiley & Sons, Ltd.
Critical role of α1‐adrenergic receptors in acute and sensitized locomotor effects of D‐amphetamine, cocaine, and GBR 12783: Influence of preexposure conditions and pharmacological characteristics
Authors: Drouin Candice , Blanc Gérard , Villégier Anne‐Sophie , Glowinski Jacques , Tassin Jean‐Pol
Published: August 2002

Psychostimulant‐induced locomotor hyperactivity is commonly associated with an inhibition of dopamine reuptake. However, a physiological coupling between noradrenergic and dopaminergic neurons occurring through the stimulation of α1‐adrenergic receptors has recently been proposed. This possibility was tested on locomotor responses induced either by D‐amphetamine and cocaine, which both interfere with noradrenergic and dopaminergic transmissions, or by GBR 12783, a specific dopamine reuptake inhibitor. In an attempt to control the effects of stress and novelty on noradrenergic neurons activity, rats were submitted to habituation procedures consisting of either a 15‐h period of habituation to the experimental environment (“long‐habituation”) or to repeated exposure to intraperitoneal saline injections for 3 consecutive days (“three‐session”). Three‐session‐exposed animals exhibited a pronounced locomotor reactivity to saline injection which did not occur after noradrenergic depletion, clonidine (20 μg/kg) or prazosin (0.5 mg/kg) pretreatments, or in long‐habituation‐preexposed animals. Cocaine and GBR 12783 locomotor hyperactivities were doubled in three‐session vs. long‐habituation‐preexposed rats, whereas D‐amphetamine responses were similar in both conditions. Prazosin (0.5 mg/kg) pretreatment reduced the acute locomotor effects of the three psychostimulants in both procedures and blocked the behavioral sensitization induced by repeated injections of D‐amphetamine (0.75 mg/kg) or cocaine (5 mg/kg). GBR 12783 (5 mg/kg) failed to induce significant behavioral sensitization. In addition to their role in the acute and sensitized locomotor responses to psychostimulants possessing different pharmacological characteristics, α1‐adrenergic receptors are involved in animal reactivity to previously experimented procedures. This suggests an implication of noradrenergic neurons in the vulnerability to psychostimulants. Synapse 43:51–61, 2002. © 2001 Wiley‐Liss, Inc.
Control of response of structures with passive and active tuned mass dampers
Authors: Rasouli S. K. , Yahyai M.
Published: August 2002

Tuned mass dampers (TMDs) and active tuned mass dampers (ATMDs) are control devices added in tall buildings to suppress the response of buildings in irregular external excitations such as earthquakes and wind. The performance of both passive and active damper systems can be assessed by parametric studies. This paper presents a brief description of the theory of passive and active tuned mass dampers. In this work, the effect of TMDs has been studied by changing the frequency ratio of the damper to the first mode of the structure. It was observed that the extra damping provided by TMDs, called effective damping, can primarily be obtained from design charts developed for this purpose. A 25‐storey building is designed and analysed using these charts as an example. The behaviour of a structure with an active tuned mass damper is investigated. The related parameters and equations of the active mass damper for the building are solved and its behaviour arising from external loads is studied. The conventional studies, which are based on white‐noise excitations, usually overestimate the performance of TMDs and ATMDs. Hence, in order to study the behaviour of a building with a TMD and an ATMD in real excitations, El‐Centro and Tabas earthquakes are selected. The results show a significant increase in the effect of TMD performance in controlling the structural displacements by using additional control devices. Copyright © 2002 John Wiley & Sons, Ltd.
Doing Business in India
Authors: Budhwar Pawan
Published: August 2002

On its independence in 1947, India was among the two most industrialized nations in Asia. Since then it
adopted a “mixed economy” approach that hindered its national growth and the optimum utilization of
its immense resources (both natural and human). To re‐establish itself as an economic force in
the region, India liberalized its economy in early 1990s. The adoption of the “free market economy”
model has created great opportunities for foreign businesses. This article provides useful information on the
complex business environment, aimed to help foreign businessmen and investors to develop a good understanding on
key background knowledge for being successful in India. It reviews Indian historical development, political
structure and climate, international relations, and economy and foreign trade. India's infrastructure,
legal framework, socio‐cultural set‐up, competitive environment, as well as market structure and
potential are also analyzed. © 2001 John Wiley & Sons, Inc.
Ecotoxicological monitoring of remediation in a coke oven soil
Authors: Mendonça E. , Picado A.
Published: August 2002

Assessment of contaminated sites is usually based on chemical analyses of hazardous compounds in soil. This is enough either to assess the environmental hazard of contaminated soil nor to evaluate the efficiency of applied remediation techniques. Information on the bioavailability of complex mixtures of xenobiotics and degradation products cannot be provided by chemical analytical data, but results from bioassays can integrate the effects of pollutants in mixtures. In the preservation of human health and environmental quality, it is important to evaluate ecotoxicological effects of contaminated industrial soils to complement the techniques of analytical chemistry. The monitoring of a coke oven soil and the evaluation of the landfarming treatment technique, conducted on‐site in a pilot scale installation, was done by a battery of ecotoxicological tests: acute, chronic, and genotoxicity tests. Contaminated soil samples revealed toxic effects for different species mainly due to high concentrations of polycyclic aromatic hydrocarbons (PAHs). After landfarming treatment, soil samples presented significant reduction in toxicity, confirming the effectiveness of the landfarming process pointed out by a significant reduction in low molecular weight PAH concentrations. Comparative analysis of the different ecotoxicological tests allowed the establishment and validation of a more suitable procedure for the monitoring of PAH contaminated soils. © 2002 by Wiley Periodicals, Inc. Environ Toxicol 17: 74–79, 2002
L‐subshell fluorescence yield ratios, ω1/ω2, ω1/ω3 and ω2/ω3, for the elements 55 ≤ Z ≤ 92
Authors: Söǧüt Ömer , Büyükkasap Erdoǧan , Ertuǧrul Mehmet
Published: August 2002

ω1/ω2, ω1/ω3 and ω2/ω3 L‐subshell fluorescence yield ratios were measured for Cs, Ba, La, Ce, Pr, Nd, Sm, Tb, Ho, Er, Yb, Ta, W, Au, Hg, Tl, Pb, Bi, Th and U at an excitation energy of 59.5 keV using an Si(Li) detector coupled to a Model 4096 computerized multi‐channel analyser. The present results are compared with other experimental values. Copyright © 2001 John Wiley & Sons, Ltd.
Application of EDXRF to the assessment of aortic valve mineralization
Authors: Wróbel A. , Rokita E. , Korbas M. , Podolec P. , Goncerz G.
Published: August 2002

Calcification of the aortic valve cusps due to degenerative changes is the most common lesion encountered in patients who require aortic valve replacement. The primary pathogenic mechanisms responsible for calcific degeneration of the aortic valves still remain unclear. Moreover, there are no convenient methods for the assessment of aortic valve susceptibility to mineralization, which is of crucial importance for the choice of valves for transplantation. The present study was undertaken to develop a quick method for the assessment of the mineralization of aortic valve samples by determination of the increase in calcium level during in vitro incubation of aorta samples. Such a method would allow one to obtain the necessary information without destruction of the material for transplantation. The study consisted in the incubation of human aorta and aortic valve samples, followed by the determination of calcium concentrations by EDXRF. The following elements were detected: Na, Mg, Al, Si, P, S, Cl, K, Fe, Ni, Cu, Zn and Br. Compton scattering was used for determination of the sample thickness. The results showed that if there is an increase in Ca level in aortic valves it is accompanied by its elevation in aorta. The study showed that EDXRF may be a useful tool for studies of mineralization processes in aortic valve and aorta samples. Copyright © 2001 John Wiley & Sons, Ltd.
Molecular cloning of CaYRB1, the Candida albicans RanBP1/YRB1 homologue
Authors: Clément Martin , Fournier Hélène , Ouspenski Ilia I. , de Repentigny Louis , Belhumeur Pierre
Published: August 2002

The yeast Ran binding protein 1 (Yrb1p) is a small protein of 23 kDa that is highly conserved among eukaryotes. It stimulates the GTPase activity of Gsp1p in the presence of the GTPase activating protein Rna1p. In addition to its role in nucleocytoplasmic transport of macromolecules, YRB1/RanBP1 could be involved in the regulation of microtubules structure and dynamics. Since microtubules are tightly associated with morphological changes, we have been interested to study the role and function of YRB1 in the pathogenic fungus Candida albicans, where there is regulated change in cellular morphology. The gene product of CaYRB1 encodes a 212 amino acid protein displaying 73% homology to the S. cerevisiae homologue. The bacterially expressed gene product has an apparent molecular weight of 35.7 kDa. We show that it can complement a S. cerevisiae yrb1 null mutant and that its mRNA does not appear to be regulated in response to conditions inducing morphological changes in C. albicans. The sequence of C. albicans YRB1 has been deposited in the GenBank database under Accession No. AF049868. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of 41 kb of the DNA sequence from the right arm of chromosome II of Schizosaccharomyces pombe
Authors: Sánchez Manuel , Revuelta José L. , del Rey Francisco , Gwilliam Rhian , Skelton Jason , Churcher Carol , Rajandream Marie‐Adèle , Wood Valerie , Barrell Bart , Lyne Rachel , Reinhardt Richard , Borzym Katja , Beck Alfred , Moreno Sergio , Domínguez Angel
Published: August 2002

We report the complete sequence of cosmid c18A7 (41 046 bp insert), located on the right arm of chromosome II of the Schizosaccharomyces pombe genome. The sequence, which partially overlaps with cosmids SPBC4F6 and SPBC336, contains 16 open reading frames (ORFs) capable of coding for proteins of at least 100 amino acid residues in length (one partial) and one small nucleolar RNA (snoRNA). Four known genes were found: swi10 (encoding a mating‐type switching protein also involved in nucleotide excision repair); dim1 (encoding a dimethyladenosine transferase); arf1 (encoding ADP‐ribosylation factor 1); and pol3 (cdc6) the partial fragment, encoding the 125 kDa catalytic subunit of the DNA polymerase type B. Six ORFs similar to known proteins were found. They include a transporter of the major facilitator superfamily class, a vacuolar sorting protein, an asparagine synthase, a nuclear protein, a reticulum oxidoreductin and a heat shock protein. Each protein product of the other six ORFs has conserved domains and can be assigned a molecular, but not a biological, function. The sequence has been submitted to the EMBL database under Accession No. AL080287. Copyright © 2001 John Wiley & Sons, Ltd.
Large‐scale phenotypic analysis reveals identical contributions to cell functions of known and unknown yeast genes
Authors: Bianchi Michele M. , Ngo Saravuth , Vandenbol Micheline , Sartori Geppo , Morlupi Alessandro , Ricci Carlo , Stefani Stefania , Morlino Giovanni B. , Hilger François , Carignani Giovanna , Slonimski Piotr P. , Frontali Laura
Published: August 2002

Sequencing of the yeast genome has shown that about one‐third of the yeast ORFs code for unknown proteins. Many other have similarity to known genes, but still the cellular functions of the gene products are unknown. The aim of the B1 Consortium of the EUROFAN project was to perform a qualitative phenotypic analysis on yeast strains deleted for functionally orphan genes. To this end we set up a simple approach to detect growth defects of a relatively large number of strains in the presence of osmolytes, ethanol, high temperature, inhibitory compounds or drugs affecting protein biosynthesis, phosphorylation level or nucleic acids biosynthesis. We have now developed this procedure to a semi‐quantitative level, we have included new inhibitors, such as hygromycin B, benomyl, metals and additional drugs interfering with synthesis of nucleic acids, and we have performed phenotypic analysis on the deleted strains of 564 genes poorly characterized in respect to their cellular functions. About 30% of the deleted strains showed at least one phenotype: many of them were pleiotropic. For many gene deletions, the linkage between the deletion marker and the observed phenotype(s) was studied by tetrad analysis and their co‐segregation was demonstrated. Co‐segregation was found in about two‐thirds of the analysed strains showing phenotype(s). Copyright © 2001 John Wiley & Sons, Ltd.
Mutant analysis reveals complex regulation of sphingolipid long chain base phosphates and long chain bases during heat stress in yeast
Authors: Ferguson‐Yankey Stacey R. , Skrzypek Marek S. , Lester Robert L. , Dickson Robert C.
Published: August 2002

Sphingolipid long chain bases (LCBs) in Saccharomyces cerevisiae, dihydrosphingosine (DHS) and phytosphingosine (PHS) and their phosphates (DHS‐P and PHS‐P) are thought to play roles in heat stress. However, quantitative studies of LCBs and LCBPs have been limited by analytical methods. A new analytical procedure allowed us to measure changes in all known LCBPs and LCBs in wild‐type and mutant cells during heat shock and to correlate the changes with heat stress resistance. All five molecular species of LCBPs increased rapidly but transiently when log and stationary phase cells were heat‐stressed and when log‐phase cells were induced for thermotolerance, suggesting that LCBPs play a role in heat stress. In support of this hypothesis, cells lacking the minor LCB kinase, Lcb5p, but not the major kinase, Lcb4p, were two‐fold less resistant to killing when log‐phase cells were induced for thermotolerance. Thus, LCBPs seem to play a minor role in heat‐stress resistance. However, their role may be masked by LCBs, which are elevated in mutant strains, such as one lacking Lcb4p. This elevation demonstrates that one function of Lcb4p is to regulate LCB levels. Two new compounds, C16 DHS and C16 DHS‐P, were identified, with the latter being degraded by the Dpl1p lyase. Our data provide a basis for determining how the basal and heat‐induced levels of individual species of LCBs and LCBPs are governed by the Lcb4p and Lcb5p kinases, the Dpl1p lyase and the Lcb3p phosphatase. Copyright © 2002 John Wiley & Sons, Ltd.
Age‐specific fecundity of mammalian populations: A test of three mathematical models
Authors: Gage Timothy B.
Published: August 2002

Empirical age‐specific fecundity distributions are often based on small samples and hence include high levels of sampling error, particularly at the older ages. One solution to this problem is to smooth the distributions using appropriate models. The aim of this article is to compare the utility of three models for smoothing and/or graduating these distributions. The three models examined are 1) the Gamma distribution, 2) the Hadwiger function, and 3) the Brass polynomial. Test data sets consist of four types of primates (including humans), Asian elephants, and Przewalski’s horse (an extinct species). The results indicate that all three models work well with a variety of mammalian data. The simplest of these models, the Brass polynomial, cannot be rejected based on available data and appears to be the optimum choice. Zoo Biol 20:487–499, 2001. © 2002 Wiley‐Liss, Inc.
Picard groups of multiplicative invariants
Authors: Lorenz Martin
Published: August 2002

Let S = kA denote the group algebra of a finitely generated free abelian group A over the field k and let G be a finite subgroup of GL(A). Then G acts on S by means of the unique extension of the natural GL(A)-action on A. We determine the Picard group Pic R of the algebra of invariants R = SG. As an application, we produce new polycyclic group algebras with nontrivial torsion in K0.
Rings of SL2( $\Bbb{C}$ )-characters and the Kauffman bracket skein module
Authors: Bullock D.
Published: August 2002

Let M be a compact orientable 3-manifold. The set of characters of SL2(

\Bbb {C}

)-representations of

\pi_1(M)

forms a closed affine algebraic set. We show that its coordinate ring is isomorphic to a specialization of the Kauffman bracket skein module, modulo its nilradical. This is accomplished by realizing the module as a combinatorial analog of the ring in which tools of skein theory are exploited to illuminate relations among characters. We conclude with an application, proving that a small manifold's specialized module is necessarily finite dimensional.
The zero-norm subspace of bounded cohomology
Authors: Soma T.
Published: August 2002

Let

\Sigma

be a closed, orientable surface of genus > 1. In this paper, non-trivial elements

\alpha

of the third bounded cohomology

H_b^3(\Sigma;\bf {R})

with

\Vert \alpha \Vert = 0

are given constructively by using both a hyperbolic metric and a singular euclidean metric on

\Sigma \times \bf {R}

. Furthermore, it is shown that the dimension of the subspace

N^3(\Sigma)

of

H_b^3(\Sigma;\bf {R})

consisting of zero-norm elements is the cardinality of the continuum.
On Macdonald's formula for the volume of a compact Lie group
Authors: Hashimoto Yoshitake
Published: August 2002

We give a simple proof of Macdonald's formula for the volume of a compact Lie group.
Approximations of stable actions on $ \Bbb {R} $-trees
Authors: Guirardel Vincent
Published: August 2002

This article shows how to approximate a stable action of a finitely presented group on an

\Bbb {R}

-tree by a simplicial one while keeping control over arc stabilizers. For instance, every small action of a hyperbolic group on an

\Bbb {R}

-tree can be approximated by a small action of the same group on a simplicial tree. The techniques we use highly rely on Rips's study of stable actions on

\Bbb {R}

-trees and on the dynamical study of exotic components by D. Gaboriau.
Curvature of curvilinear 4-webs and pencils of one forms: Variation on a theorem of Poincaré, Mayrhofer and Reidemeister
Authors: Nakai I.
Published: August 2002

A curvilinear d-web W = (F1 , . . . , Fd) is a configuration of d curvilinear foliations Fi on a surface. When d = 3, Bott connections of the normal bundles of Fi extend naturally to equal affine connection, which is called Chern connection. For 3 < d, this is the case if and only if the modulus of tangents to the leaves of Fi at a point is constant. A d-web is associative if the modulus is constant and weakly associative if Chern connections of all 3-subwebs have equal curvature form. We give a geometric interpretation of the curvature form in terms of fake billiard in §2, and prove that a weakly associative d-web is associative if Chern connections of triples of the members are non flat, and then the foliations are defined by members of a pencil (projective linear family of dim 1) of 1-forms. This result completes the classification of weakly associative 4-webs initiated by Poincaré, Mayrhofer and Reidemeister for the flat case. In §4, we generalize the result for n + 2-webs of n-spaces.
Un théorème de rigidité différentielle
Authors: Bessières Laurent
Published: August 2002

Nous démontrons dans cet article le résultat de rigidité suivant, concernant le volume minimal d'une variété lisse fermée de dimension

\ge 3

. Théorème: soient N et M deux variétés lisses, fermées, orientées de même dimension

n \ge 3

. On suppose que M est munie d'une métrique hyperbolique g0. Si

f : N \rightarrow M

est une application continue de degré non nul telle que

{\rm Minvol} (N) = | \deg f | {\rm vol}_{g_0} (M)

, alors N est une variété hyperbolique et f est homotope à un revêtement riemannien. La preuve repose sur l'utilisation de théorèmes de convergence riemannienne à la Gromov [GLP], et sur l'adaptation de la construction de Besson, Courtois, Gallot [BCG]. L'une des applications intéressantes est que le volume minimal n'est pas un invariant du type topologique de la variété, mais de la structure différentielle. Il n'est pas non plus additif par somme connexe.
S.A.G.B.I. bases for rings of formal modular seminvariants
Authors: Shank R. J.
Published: August 2002

We use the theory of S.A.G.B.I. bases to construct a generating set for the ring of invariants for the four and five dimensional indecomposable modular representations of a cyclic group of prime order. We observe that for the four dimensional representation the ring of invariants is generated in degrees less than or equal to 2p-3, and for the five dimensional representation the ring of invariants is generated in degrees less than or equal to 2p-2.
Schubert polynomials and Bott-Samelson varieties
Authors: Magyar Peter
Published: August 2002

Schubert polynomials generalize Schur polynomials, but it is not clear how to generalize several classical formulas: the Weyl character formula, the Demazure character formula, and the generating series of semistandard tableaux. We produce these missing formulas and obtain several surprising expressions for Schubert polynomials. The above results arise naturally from a new geometric model of Schubert polynomials in terms of Bott-Samelson varieties. Our analysis includes a new, explicit construction for a Bott-Samelson variety Z as the closure of a B-orbit in a product of flag varieties. This construction works for an arbitrary reductive group G, and for G = GL(n) it realizes Z as the representations of a certain partially ordered set. This poset unifies several well-known combinatorial structures: generalized Young diagrams with their associated Schur modules; reduced decompositions of permutations; and the chamber sets of Berenstein-Fomin-Zelevinsky, which are crucial in the combinatorics of canonical bases and matrix factorizations. On the other hand, our embedding of Z gives an elementary construction of its coordinate ring, and allows us to specify a basis indexed by tableaux.
A factorization of the Conway polynomial
Authors: Levine J.
Published: August 2002

It is shown that the Conway polynomial of a link is a product of two factors, the first of which is the Conway polynomial of a knot obtained by banding together the link components and the second is determined, via an explicit formula, by the

\tilde\mu

-invariants of the link. In particular we get a formula, in terms of the 7-invariants, for the first non-zero coefficient of the Conway polynomial. A similar formula is obtained for the multi-variable Alexander-polynomial.
Acyclic covers
Authors: Millson John J.
Published: August 2002

The following question, which is directly related to the Whitehead problem of subcomplexes of acyclic 2-complexes, is studied: If

\frak P

is a class of groups, X is a 2-dimensional CW-complex and X' is an acyclic, infinite cyclic cover of X with

\pi_1(X')

in

\frak P

, must X' be contractible? A positive answer is given if X is finite and

\frak P

is the class of amenable groups.
The conjugacy problem for Dehn twist automorphisms of free groups
Authors: Cohen M. M. , Lustig M.
Published: August 2002

A Dehn twist automorphism of a group

G

is an automorphism which can be given (as specified below) in terms of a graph-of-groups decomposition of

G

with infinite cyclic edge groups. The classic example is that of an automorphism of the fundamental group of a surface which is induced by a Dehn twist homeomorphism of the surface. For

G = F_n

, a non-abelian free group of finite rank

n

, a normal form for Dehn twist is developed, and it is shown that this can be used to solve the conjugacy problem for Dehn twist automorphisms of

F_n

.
A character formula for a family of simple modular representations of $ GL_n $
Authors: Mathieu Olivier , Papadopoulo Georges
Published: August 2002

Let

K

be an algebraically closed field of finite characteristic

p

, and let

n\geq 1

be an integer. In the paper, we give a character formula for all simple rational representations of

GL_{n}(K)

with highest weight any multiple of any fundamental weight. Our formula is slightly more general: say that a dominant weight

5

is special if there are integers

i\leq j

such that

\lambda=\sum_{i\leq k\leq j}a_{k}\,\omega_{k}

and

\sum_{i\leq k\leq j} a_k\leq {\rm inf}(p-(j-i),p-1)

. Indeed, we compute the character of any simple module whose highest weight

5

can be written as

\lambda=\lambda_{0}+p\lambda_{1}+...+p^{r}\lambda_{r}

with all

\lambda_{i}

are special. By stabilization, we get a character formula for a family of irreducible rational

GL_{\infty}(K)

-modules.
Isotopy and invariants of Albert algebras
Authors: Thakur Maneesh L.
Published: August 2002

Let k be a field with characteristic different from 2 and 3. Let B be a central simple algebra of degree 3 over a quadratic extension K/k, which admits involutions of second kind. In this paper, we prove that if the Albert algebras

J(B,\sigma,u,\mu)

and

J(B,\tau,v,\nu)

have same

f_3

and

g_3

invariants, then they are isotopic. We prove that for a given Albert algebra J, there exists an Albert algebra J' with

f_3(J')=0

,

f_5(J')=0

and

g_3(J')=g_3(J)

. We conclude with a construction of Albert division algebras, which are pure second Tits' constructions.
Projectively equivalent metrics, exact transverse line fields and the geodesic flow on the ellipsoid
Authors: Tabachnikov S.
Published: August 2002

We give a new proof of the complete integrability of the geodesic flow on the ellipsoid (in Euclidean, spherical or hyperbolic space). The proof is based on the construction of a metric on the ellipsoid whose non-parameterized geodesics coincide with those of the standard metric. This new metric is induced by the hyperbolic metric inside the ellipsoid (Klein's model).
On $ \pi $-hyperbolic knots and branched coverings
Authors: Paoluzzi L.
Published: August 2002

We prove that, for any given

n > 2

, a

\pi

-hyperbolic knot is determined by its 2-fold and n-fold cyclic branched coverings. We also prove that a

2\pi/m

-hyperbolic knot which is not determined by its m-fold and n-fold cyclic branched coverings,

2 < m < n

, must have genus

(n - 1)(m - 1)/2

.
Mutation and gauge theory I: Yang-Mills invariants
Authors: Ruberman Daniel
Published: August 2002

Mutation of 3-manifolds (cutting and regluing along a genus 2 surface using a central involution) is shown to preserve the instanton Floer homology of homology 3-spheres. A related operation on 4-manifolds is shown to preserve the Donaldson polynomial invariant.
Hausdorff dimension and conformal dynamics II: Geometrically finite rational maps
Authors: McMullen Curtis T.
Published: August 2002

This paper investigates several dynamically defined dimensions for rational maps f on the Riemann sphere, providing a systematic treatment modeled on the theory for Kleinian groups. We begin by defining the radial Julia set Jrad(f), and showing that every rational map satisfies

{\rm H.\,dim}\,J_{{\rm rad}}(f) = \alpha(f)

where

\alpha(f)

is the minimal dimension of an f-invariant conformal density on the sphere. A rational map f is geometrically finite if every critical point in the Julia set is preperiodic. In this case we show {\rm H.\,dim}\,J_{{\rm rad}}(f) = {\rm H.\,dim}\,J(f) = \delta (f)

, where

\delta(f)

is the critical exponent of the Poincaré series; and f admits a unique normalized invariant density 7 of dimension

\delta(f)

. Now let f be geometrically finite and suppose

f_n \to f

algebraically, preserving critical relations. When the convergence is horocyclic for each parabolic point of f, we show fn is geometrically finite for

n \gg 0

and

J(f_n) \to J(f)

in the Hausdorff topology. If the convergence is radial, then in addition we show

{\rm H.\,dim}\,J(f_{n}) \to {\rm H.\,dim}\,J(f)

. We give examples of horocyclic but not radial convergence where

{\rm H.\,dim}\,J(f_{n}) \to 1 > {\rm H.\,dim}\,J(f) = 1/2 + \epsilon

. We also give a simple demonstration of Shishikura's result that there exist

f_n(z) = z^2 + c_n

with

{\rm H.\,dim}\,J(f_{n}) \to 2 $. The proofs employ a new method that reduces the study of parabolic points to the case of elementary Kleinian groups.
Quasi-isometries of groups, graphs and surfaces
Authors: Maillot Sylvain
Published: August 2002

We give a characterization of virtual surface groups as groups quasi-isometric to complete simply-connected Riemannian surfaces. Results on the equivalence up to quasi-isometry of various bounded geometry conditions for Riemannian surfaces are also obtained.
The group of self-distributivity is bi-orderable
Authors: Dehornoy Patrick
Published: August 2002

We prove that the group of left self-distributivity, a cousin of Thompson's group F and of Artin's braid group

B_\infty

that describes the geometry of the identity x(yz) = (xy)(xz), admits a bi-invariant linear ordering. To this end, we define a partial action of this group on finite binary trees that preserves a convenient linear ordering.
Oxalate and Urinary Stones
Authors: Ogawa Yoshihide , Miyazato Tomonori , Hatano Tadashi
Published: August 2002

Abstract

Calcium oxalate is a major component of renal stones, and its urinary concentration plays an important role in stone formation. Even a small increase in urinary oxalate has a significant impact on calcium oxalate saturation. Although primary hyperoxaluria is relatively uncommon, patients with calcium oxalate stones have some degree of hyperoxaluria. To understand the underlying causes of such hyperoxaluria, the processes of oxalate synthesis and excretion must be clarified. This article focuses on the determination of oxalate, calculation of its saturation, and the hyperoxaluric syndromes with special reference to metabolic precursors of oxalate, including ascorbic acid, glyoxylate, and glycolate.
Role of Esophagectomy in Treatment of Esophageal Carcinoma with Clinical Evidence of Adjacent Organ Invasion
Authors: Matsubara Toshiki , Ueda Mamoru , Kokudo Norihiro , Takahashi Takashi , Muto Tetsuichiro , Yanagisawa Akio
Published: August 2002

With carcinoma of the thoracic esophagus, clinical evidence of invasion of adjacent organs (T4) indicates a highly advanced stage, and most surgeons avoid esophagectomy. Although the therapeutic strategy for such disease is generally selected based on preoperative evaluation and intraoperative inspection, their accuracy and the relation to survival outcomes after esophagectomy have seldom been analyzed on the basis of exact histopathologic evidence. We performed esophagectomy, with perioperative adjuvant therapy when possible, on patients with clinical‐T4 tumors unless absolutely unresectable conditions were detected. Among the 500 patients who underwent esophagectomy, the 78 patients whose tumors were confirmed to be T4 pathologically were compared with patients whose tumors were assessed as T4 preoperatively or intraoperatively to evaluate the role of esophagectomy for clinical‐T4 carcinoma. Esophagectomy was possible for 99% of the pathologic‐T4 tumors preoperatively assessed as resectable, but the resection was grossly incomplete in 35%. The true‐positive rates in tumors preoperatively and intraoperatively assessed as T4 were 51% and 84%, respectively. The hospital mortality rate in patients with pathologic‐T4 tumors was 4%. The overall 5‐year survival rate for patients with pathologic‐T4 tumors was 14%, compared with 60% for those with tumors assessed as T4 intraoperatively but not pathologically. Esophagectomy with perioperative adjuvant therapy yielded occasional cure with an acceptable mortality rate for patients with pathologic‐T4 tumors assessed as technically resectable. Preoperative assessment and intraoperative macroscopic inspection had limitations for predicting pathologic‐T4 disease and incomplete resection. Only patients with definitive evidence of unresectability should be excluded from esophagectomy.
Pseudotumor Developing in Heterotopic Pancreas
Authors: Fékété F. , Noun R. , Sauvanet A. , Fléjou J.F. , Bernades P. , Belghiti J.
Published: August 2002

Cystic dystrophy in heterotopic pancreas (CDHP) is characterized by the presence of cystic formations surrounded by inflammation and scarring. It usually involves the duodenal wall and can be responsible for strictures and pain. The diagnosis of this disorder was previously based on pancreatoduodenectomy specimens removed for a suspected pancreatic tumor. Six cases were observed in young men (mean age 40 years) between 1989 and 1993. Computed tomography (CT) and endoscopic ultrasonography (EUS) features allowed definitive preoperative diagnosis of CDHP. After surgical resection of the tissue‐bearing segments that included five pancreatoduodenectomies and one antrectomy, symptoms disappeared in all patients. Patients were followed 2 to 45 months; one patient experienced recurrence of pain and hyperamylasemia 17 months after surgery. The preoperative diagnosis of CDHP is presently possible because of modern imaging procedures and improved knowledge of specific signs. Resection is the most appropriate treatment.
Parathyroid Incidentalomas in Normocalcemic Patients during Thyroid Surgery
Authors: Carnaille Bruno M. , Pattou François N. , Oudar Christophe , Lecomte‐Houcke Martine C. , Rocha José E. , Proye Charles A.
Published: August 2002

The aim of this study was to compare the clinical, biochemical, and pathologic findings of normocalcemic patients with macroscopically enlarged parathyroid tissue identified at thyroid surgery with those of patients treated surgically for preoperatively proved primary hyperparathyroidism (PHPT). The records of 28 patients with incidental parathyroid enlargement and 533 patients with PHPT were reviewed to compare age, sex, serum calcium and phosphate, intact parathyroid hormone (iPTH), parathyroid weight, number of diseased glands, cell and histologic types, PTH content, and cure rate. Incidentally found lesions were lighter and developed in younger patients. Biochemistry and pathology found them to be less hyperfunctioning. Sex, number of diseased glands per patient, and cell type were not different. PTH content was low in the incidental lesions. Incidentally discovered enlarged parathyroid glands are mildly hyperfunctioning at the time of discovery. They may represent an early stage of lesion responsible for overt PHPT. In the absence of knowledge concerning their significance and evolution, we recommend that enlarged parathyroids found during the course of a thyroid operation be removed.