bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards enhancing survivors' organizational and personal reactions to layoffs: A rejoinder to daniels
Authors: Brockner Joel
Published: May 2007

In this issue Daniels critiques a report which appeared in the Strategic Management Journal's Special Issue on Corporate Restructuring. The report described two studies which delineated several determinants of the reactions of layoff survivors (Brockner et al., 1993). Daniels interpreted Brockner et al. to be saying that managers in downsizing organizations should implement layoffs in ways that maximize survivors' organizationally‐relevant reactions. even if doing so imposes personal costs on the survivors. Unfortunately, Daniels failed to perceive our intended message: that layoffs (and other forms of restructuring) should be implemented in ways that optimize outcomes for both the organization and its people.
Relational governance as an interorganizational strategy: An empirical test of the role of trust in economic exchange
Authors: Zaheer Akbar , Venkatraman N.
Published: May 2007

We develop a model of relational governance as a specific form of interorganizational strategy that is distinct from the traditional modes of markets and hierarchies. We conceptualize this form of strategy in terms of structural and processual dimensions and derive a model of its determinants through arguments drawn from transaction cost economics and the sociological exchange literature. Hierarchical regression modeling is employed to test the theoretical model on data collected from a sample of 329 independent insurance agencies. We include the relational variable of trust and demonstrate that the combined model explains relational governance better than a model with the traditional determinants of governance form alone. Further, we observe that governance structure and process are related and discuss implications of the dynamic link between them. Directions for extensions are developed for strategic management research and practice.
CEO and director turnover in failing firms: An illusion of change?
Authors: Daily Catherine M. , Dalton Dan R.
Published: May 2007

Firms facing imminent bankruptcy would seemingly be under some pressure to demonstrate effective governance structures as a means for maintaining the support of important external constituents and initiating a turnaround. Little is known, however, about CEO and director turnover and its impact on the composition and structure of the board in failing firms. This study assesses both the incidence and form of governance changes in the 5‐year period prior to corporate bankruptcy. Despite extensive board member and CEO replacements. changes by firms at imminent risk of failure do not conform with the prescriptions favored by reform advocates and institutional investors.
A note on corporate strategy and capital structure
Authors: Taylor Peter , Lowe Julian
Published: May 2007

The relationships between capital structure and corporate strategy in previous U.S. and Australian empirical studies, which use different definitions of capital structure, and hence have different functional relationships, are considered. A model using the U.S. specification with the Australian data is estimated, for which previous conclusions relating to profit are confirmed. The relationship between strategy and capital structure is thus shown to be less than robust. The conclusion that debt/equity ratios of highly diversified firms are more strongly affected by firm‐level variables is supported. An explanation that the capital market rewards focused firms because they are easier to understand and price is offered.
Strategic groups as reference groups: Theory, modeling and empirical examination of industry and competitive strategy
Authors: Fiegenbaum Avi , Thomas Howard
Published: May 2007

Previous studies on strategic groups have mainly focused on their static characteristics in order to test the theory of strategic groups and intraindustry performance differences (Porter, 1979; Cool and Schendel, 1988; Fiegenbaum and Thomas, 1990). In contrast, this study takes a longitudinal, dynamic perspective and describes the forces driving strategic group membership and structural evolution. It proposes that a strategic group acts as a reference point for group members in formulating competitive strategy. A partial adjustment model of strategic mobility is then developed which incorporates the idea of a strategic group as a reference group. It models strategic change in an industry both within and across strategic groups. The model is tested in the context of an in‐depth industry analysis of the more significant firms in the insurance industry over the 1970‐84 time period. The results suggest that strategic groups act as reference points for firm strategies and that predictions of future firm strategies and industry/group structures may also be successfully derived.
The science of complexity: An alternative perspective for strategic change processes
Authors: Stacey Ralph D.
Published: May 2007

The two perspectives of strategy process most firmly established in the literature—strategic choice and ecology—assume the same about system dynamics: negative feedback processes driving successful systems (individual organizations or populations of organizations) toward predictable equilibrium states of adaptation to the environment. This paper proposes a third perspective, that of complex adaptive systems. The framework is provided by the modern science of complexity: the study of nonlinear and network feedback systems, incorporating theories of chaos, artificial life, self‐organization and emergent order. Here system dynamics are characterized by positive and negative feedback as systems coevolve far from equilibrium, in a self‐organizing manner, toward unpredictable long‐term outcomes.
The problem of unobservables in strategic management research
Authors: Godfrey Paul C. , Hill Charles W. L.
Published: May 2007

In this paper we argue that unobservable constructs lie at the core of a number of influential theories used in the strategic management literature—including agency theory, transaction cost theory, and the resource‐based view of the firm. The debate over how best to deal with the problem of unobservables has raged in the philosophy of science literature for the best part of the current century. On the one hand, there are the positivists, who believe that theories containing unobservable constructs are only useful as tools for making predictions. According to positivists, such theories do not inform us about the deep structure of reality. On the other hand, there are the realists, who believe that our theories can give us knowledge about unobservables. Herein we review this debate, we argue for adopting a realist position, and we draw out the implications for strategic management research.
Profiles of managerial activities in small firms
Authors: Russell Merz G. , Sauber Matthew H.
Published: May 2007

This paper addresses the contingency issues of managerial activities and reports the results of a study that configures such activities in small firms. In a survey of CEOs and top executives, data on planning, organizing, and controlling activities as well as entrepreneurial orientation and environmental turbulence were collected and used in the development of a taxonomy. Findings demonstrate that (1) small firms can be classified based on perceived differences in strategy, structure, and the environments they face, and (2) they display managerial and structural consistency when faced with similar contextual situations. The taxonomy developed in this study suggests that four distinct configurations describe the managerial profiles among small firms. Each profile and its corresponding contingency characteristics are discussed and managerial and research implications elaborated.
Cooperative strategy and new venture performance: The role of business strategy and management experience
Authors: McGee Jeffrey E. , Dowling Michael J. , Megginson William L.
Published: May 2007

This paper reports the results of a study of new ventures which examine the relationships between performance and the experience of a new venture's management team, its choice of competitive strategy, and its use of various cooperative arrangements. The findings of the moderated regression analysis indicate that cooperative arrangements are most beneficial to those new ventures whose management teams possess the most experience.
Recreating and extending Japanese automobile buyer'supplier links in north America
Authors: Martin Xavier , Mitchell Will , Swaminathan Anand
Published: May 2007

We compare buyer'supplier links established by pairs of Japanese‐owned automobile assemblers and component manufacturers operating in Japan and in North America during 1989‐90. Eight assemblers and more than 170 Japanese component manufacturers had established North American manufacturing facilities. In total, Japanese automobile assembly organizations operating in North America had recreated about a quarter of their Japanese supply links. The suppliers that set up North American facilities had recreated almost 60 percent of their links with traditional buyers and formed more than 16 percent of the possible extension links with new assembler partners. We identify several economic and organizational factors that influence whether an existing buyer'supplier link will be recreated in a new location and whether firms that do not have a buyer'supplier relationship at home will form an extension link in the new location. We find that the presence of a long‐term buyer'supplier relationship, buyer and supplier entry timing to the new location, the joint venture status of the buyer, supplier size, and the breadth of a supplier's sales base in the home market influence the likelihood that links will be recreated and extension links will be formed.
The role of strategic alliances in high‐technology new product development
Authors: Kotabe Masaaki , Scott Swan K.
Published: May 2007

The authors examined 905 new product innovations introduced since September 1988 to determine the influences on product innovativeness, with a specific interest in strategic alliances, or cooperative strategies. Findings suggest that single firms, horizontal cooperative strategies, small and mixed'sized firms, biochemical industries, cross‐industry product offerings, cross‐industry cooperations, the progression of time, and European firms tend to indicate significantly more innovative products. Implications are proposed for business practitioners and researchers with specific application to the diffusion of innovation.
Structural and competitive determinants of a global integration strategy
Authors: Birkinshaw Julian , Morrison Allen , Hulland John
Published: May 2007

Both structural determinants and competitive factors can work to define the relevant environment for strategy formulation within an industry. This study examines the effects of each of these two sets of factors on global integration strategies, and finds that their impacts vary considerably from one industry to another. The study also investigates the relationship between a business's global integration strategy and its performance, using an industry'specific perspective. In the aggregate, the businesses studied appear to be under‐globalized. However, this relationship varied significantly by industry; four of the industries studied appeared to be under‐globalized, while the remaining three industries were at or near an optimal level of globalization.
Herstellung funktionaler organischer Dünnschichten durch Vakuumverdampfung
Authors: Drechsel Jens
Published: May 2007

Das Aufdampfen unter Hochvakuum‐ oder Ultrahochvakuum‐Bedingungen ist eine seit fast hundert Jahren beherrschte Methode um funktionale dünne Schichten herzustellen. Seit der Entdeckung halbleitender Kunststoffe um 1970/80 wird dieses Verfahren zunehmend auch zur Erzeugung dünner organischer Schichten verwendet. Momentan stehen insbesondere Materialien für organisches LEDs (OLEDs) sowie Dünnschicht‐Solarzellen im Mittelpunkt des Interesses. Das Verdampfen von Organika benutzt die Vorzüge der bekannten Hochvakuumverfahren (Reinheit, kompatible Prozesse, Nutzung von Masken, usw), bildet jedoch auch neue Herausforderungen an die Prozess‐Steuerung. Der Artikel beschreibt sowohl die grundsätzlichen Anforderungen, Fähigkeiten aktueller temperaturgeregelter Verdampferquellen, Material‐Aspekte, als auch typische technische Anwendungen.
Application of the Theory of Fracture on the Surface of Instability
Authors: Makky S. M.
Published: May 2007

In a previous paper by the author [1], fracture surfaces of round bars under pure torsion are considered. To exclude the effects on the stress distribution of the displacements along the axis of the bar, it was assumed that the bar is made of plastic‐rigid material. This insured that the bar remained in pure torsion. In this paper a more realistic case is considered which includes the effects of the axial stress in a round bar under torsion when the two ends of the bar are confined to lie in fixed planes. Such a case will be denoted by the shorter term „fixed ends”︁, and the therm „free ends”︁ will be used when there is no such restriction. For the case of pure torsion it was shown that the bar is most likely to fracture on a helicoidal surface whose intersection with the cylindrical surface of the bar is a helix making a 45º with the generator of the cylinder. In this paper, it is shown that a bar with fixed ends under torsion is subject to fracture along a cross section.
Optimum One‐term Solutions for Heat Conduction Problems
Authors: Kleinstein G. , Ting L.
Published: May 2007

A series solution in descending powers of time is developed for heatconduction problems with initial profiles prescribed at an instant t* > 0. The leading term of the series solution, the first eigensolution, represents a source with strength given by the integral of the initial profile. It is shown that the coefficients of the eigensolutions corresponding to the second eigenvalue can be equated to zero when the origin is shifted to the center of gravity of the initial profile and that the coefficient of the symmetric eigensolution of the third eigenvalue will vanish when the time shift t* is related to the second moment of the initial profile. The first eigensolution with these optimum shifts in space and time variables yields an optimum one term representation of the exact solution as time increases. The optimum solution fulfills two properties of the exact solution, the conservation of energy integral and the invariance of the center of gravity of the temperature profile. Proofs for these properties of the exact solution are presented.
Über intervallmäßige Iterationsverfahren bei linearen Gleichungssystemen und allgemeineren Intervallgleichungssystemen
Authors: Mayer O.
Published: May 2007

Die vorliegende Arbeit behandelt Anwendungen der Intervallrechnung bei der iterativen Auflösung linearer Gleichungssysteme: Zunächst wird ein Überblick gegeben über das Konvergenzverhalten von Gesamtschritt‐, Einzelschritt‐ und Relaxationsverfahren bei allgemeineren Gleichungen in Intervallräumen; dann wird die Bedeutung dieser Intervallgleichungen für die Bestimmung von Schranken für die Lösungen linearer Gleichungssysteme mit ungenauen Koeffizienten aufgezeigt. Abschließend wird die praktische Durchführung der Iterationsverfahren unter dem Gesichtspunkt der Rundungsfehlererfassung behandelt.
On Complex Potentials in Micropolar Elasticity
Authors: Ariman T. , Zika M. J.
Published: May 2007

The aim of this paper is to investigate the possibility of the use of the theory of micropolar continua in the analysis of microcracks. As an initial step of the microfracture mechanics, the complex variable technique of the classical theory of elasticity is extended to the micropolar elasticity. The first fundamental problem of Muskhelishvili, the problem of a circular hole in an infinite plate, is solved.
Optimale Fehlerschranken für die Lösung von Differentialgleichungssystemen erster Ordnung bei Verwendung von Funktionstafeln
Authors: Tutschke W.
Published: May 2007

Betrachtet wird die Lösung des Systems y'j = fj(…) mit vorgeschriebenen Anfangswerten. Falls die Funktionswerte der fj nur mit der Genauigkeit Δ gegeben sind und falls |fj| ≦ K0 ist, so sei k* die kleinste natürliche Zahl, für die K0 ≦ Δ (k☆ + 2) ! ist. Dann erhält man für die k☆‐te Näherung (im Sinn der Methode der sukzessiven Approximationen) die kleinste Fehlerschranke.
Die Schrittweite beim Gradientenprojektionsverfahren für Probleme der optimalen Steuerung
Authors: Glashoff K.
Published: May 2007

Für eine Klasse linearer Steuerungsprobleme mit quadratischem Funktional wird die Schrittweite für das Gradientenprojektions‐Näherungsverfahren angegeben. Der Konvergenzbeweis für das Verfahren mit der hier berechneten Schrittweite beruht auf einem Satz von Goldstein über Gradientenmethoden im Hilbertraum. Der letzte Abschnitt gibt einen Hinweis auf die Schwierigkeiten, die bei nichtlinearen Steuerungsaufgaben auftreten, und ein Gegenbeispiel zur Fréchet‐Differenzierbarkeit des zu minimierenden Funktionals.
Autokorrelationstests und autoregressive Schätzverfahren
Authors: Schips B. , Stier W.
Published: May 2007

Diese Arbeit soll zeigen, daß alternative Testverfahren für die Hypothese nicht autokorrelierter Störvariablen in linearen Regressionsmodellen und alternative autoregressive Schätzverfahren im Falle autokorrelierter Störvariablen zu erheblichen Unterschieden in den numerischen Ergebnissen führen können. Die Unterschiede in den Schätzwerten, die auf alternative Schätzverfahren zurückgehen, sind dabei in vielen Fällen erheblicher als bei Verwendung alternativer Modelle.
Über eine Erweiterung der Monte‐Carlo‐Methode zur Lösung linearer Randwert‐probleme zweiter und dritter Art
Authors: Hartmann W.
Published: May 2007

Die sequentielle Monte‐Carlo‐Methode mit Informationsspeicherung wird angewendet auf Randwertprobleme zweiter und dritter Art, indem die Randbedingungen iterativ durch Relaxation aus dem Gitterinnern realisiert werden. Als Spezialfall ist im Verfahren die Anwendung der sequentiellen Monte‐Carlo‐Methode auf Randwertprobleme erster Art enthalten.
Hinreichende Bedingung für Ausschluß von Eigenwerten in Parameterintervallen bei einer Klasse von linearen homogenen Funktionalgleichungen
Authors: Spreuer H. , Adams E.
Published: May 2007

Es werden lineare homogene Systeme von gewöhnlichen oder elliptischen Funktional‐ bzw. Differentialgleichungen oder von gewöhnlichen Gleichungen mit einem freien Parameter Λ betrachtet. Koeffizienten müssen Vorzeichenbedingungen erfüllen. In Satz 1 wird gezeigt, daß Λ kein Eigenwert ist, wenn eine solche Vektorfunktion v mit nur positiven Komponenten existiert, daß die Operatoren des Systems in den jeweiligen Gültigkeitsgebieten überall positive Werte annehmen, nachdem v eingesetzt worden ist. In Satz 2 wird gezeigt, daß diese Operatoren unter den Bedingungen von Satz 1 Aufgaben von monotoner Art erklären. Die Beweise erfolgen im Rahmen der Theorie der Differential‐ und Integralungleichungen. In den fünf Beispielen werden Funktionen v für die folgenden Fälle angegeben: schwingende Platte, monoenergetischer Neutronenreaktor, eine chemisch reagierende Strömung, nichtlinearer Knickstab und Mathieusche Dgl.
On the Region of Convergence of Picard's Iteration
Authors: van de Craats J.
Published: May 2007

A new convergence condition is described for Picard's iteration for the boundary value problem

where f(t, y, z) is continuous and satisfies a Lipschitz‐condition in y and z. This convergence condition is optimal in a sense specified precisely in this paper.
Zur Steuerung der Stabilität in elastischen Körpern
Authors: Beckert H.
Published: May 2007

Es wird gezeigt, daß man die Stabilitätsgrenzen (Eigenwerte) einer dünnen Platte durch Abänderung der in der Plattenebene wirkenden Randkräfte entlang eines beliebig kleinen Randstücks weitgehend steuern kann. Entlang der Trefftzschen Stabilitätstheorie gelingt die Übertragung auf räumliche Probleme. Liegen die Randkräfte in einer beschränkten konvexen Menge eines reflexiven Banachraums, so existieren optimale Steuervektoren.
Überlinear konvergente Mehrschrittverfahren vom Regula falsi‐ und Newton‐Typ
Authors: Schmidt J. W.
Published: May 2007

Ausgehend von der Regula falsi und dem Newton‐Verfahren zur Lösung von nichtlinearen Gleichungssystemen werden Mehrschrittverfahren entwickelt, welche sich gegenüber den Standardverfahren hinsichtlich der Effektivität in zwei Punkten auszeichnen: Sie haben einen höheren Wirkungsgrad schon dann, wenn man für den Aufwand allein die Anzahl der Funktionswertberechnungen berücksichtigt. Zusätzlich bringt die jetzt mögliche Anwendung der Formel von Sherman und Morrison bei der in jedem Iterationsschritt erforderlichen Auflösung von linearen Gleichungssystemen Einsparungen mit sich. Breiten Raum nimmt die Herleitung eines allgemeinen Konvergenzsatzes ein; er enthält als Sonderfälle den bekannten Satz von Kantorovich über das Newton‐Verfahren und einen entsprechenden Satz über die Regula falsi.
Über zulässige Schrittweiten bei den Adams‐Verfahren
Authors: Weissinger J.
Published: May 2007

Die Anwendung eines Differenzenverfahrens auf das Anfangswertproblem einer Differentialgleichung y′ = ‐ A y führt auf eine lineare, homogene Differenzengleichung zur Bestimmung der Näherungswerte yn ≈ y (x0 + n h). Von einer zulässigen Schrittweite h muß man lim yn = 0 im Falle A > 0 fordern. Für die Verfahren von Adams‐n→∞ Bashforth, Adams‐Moulton, Nyström und Milne‐Simpson werden die h‐Intervalle bestimmt, in denen diese Forderung für alle Lösungen der Differenzengleichung erfüllt ist.
Potentialströmung um N Kreise
Authors: Weizel R.
Published: May 2007

Es wird die ebene Potentialströmung um endlich viele, einfach geschlossene Hindernisse untersucht. Die Berechnung des komplexen Potentials wird hier auf die Lösung eines modifizierten Dirichletschen Problems [1] zurückgeführt. Das Lösungsverfahren wird numerisch ausgewertet für den Fall einer Strömung im Außengebiet dreier Kreise.
Yield Criterion and the Hardening Rule for a Plastic Solid
Authors: Shrivastava H. P. , Mróz Z. , Dubey R. N.
Published: May 2007

The work‐hardening of an initially isotropic material is mathematically described by a hardening rule which specifies the modification of the initial yield condition in the process of continued plastic deformation. Although such rules have been proposed by various investigators and shown to be in good agreement with the experimental results, they are based on different specific assumptions. In the present work it is shown that all the existing hardening rules can be obtained from a general mathematical concept which is based upon the isotropic representation of a scalar valued function which is a function of two symmetric 3 × 3 matrices. A more general form has then been derived which accounts for the second‐order effect relating to axial strain accumulation in cyclic torsion.
Some Two‐Dimensional Exterior Problems in a Linear Elastic Solid of Grade Two
Authors: Eshel N. N. , Rosenfeld G.
Published: May 2007

Solutions are given to four two‐dimensional exterior problems in a linear, mechanically homogeneous, isotropic and centrosymmetric elastic solid of grade two (Toupin [1], p. 87). bounded internally by a circular cylindrical cavity. The solutions are found to be size dependent and to exhibit boundary layer effects. The results are compared to the corresponding results in classical elasticity, couple‐stress theory and micropolar elasticity.
Some Extremum Principles for Mixed Boundary Value Problems in Magnetohydrodynamic Pipe Flow
Authors: Smith P.
Published: May 2007

Some extremum principles are established for the rectilinear flow of a fluid in a pipe under the influence of a uniform magnetic field. The pipe walls are composed of non‐conducting and conducting segments. Bounds are deduced for the mass‐flow rate which can be used to construct asymptotic formulae valid for large Hartmann numbers. Several illustrative examples are included.
A Theoretical Investigation of Finite Amplitude Thermal Convection in Non‐Newtonian Fluids
Authors: van der Borght R. , Murphy J. O. , Steiner J. M.
Published: May 2007

Für den Fall sechseckigen Umrisses einer Konvektionszelle endlicher Länge werden die Grundgleichungen hergeleitet, die die Wärmekonvektion in einer nichtnewtonschen Flüssigkeit beschreiben. Ihre numerische Lösung zeigt im Falle zweier freier Ränder, daß die viskoelastischen Effekte die Nusselt‐Zahl nur wenig ändern. Immerhin ist die Nusselt‐Zahl bei gegebener Rayleigh‐Zahl durchweg — wenn auch nur wenig — größer als bei einer newtonschen Flüssigkeit vergleichbarer Viskosität. Diese theoretischen Voraussagen stehen im Einklang mit neueren experimentellen Ergebnissen im Falle zweier starrer Ränder.
Transient Stresses in an Elastic Half Space Resulting from the Frictionless Indentation of a Rigid Wedge‐Shaped Die
Authors: Robinson A. R. , Thompson J. C.
Published: May 2007

Für das im Titel genannte Problem erhält man eine im Rahmen der klassischen Elastizitätstheorie exakte Lösung, wenn man annimmt, daß der Halbraum homogen und isotrop ist und der Keil mit konstanter Geschwindigkeit eindringt. Für eine gegebene Form des Keiles und des elastischen Mediums bestimmt die Eindringgeschwindigkeit eindeutig die Geschwindigkeit der vom Rande weg sich ausdehnenden Kontaktzone. Diese Geschwindigkeit, verglichen mit den Geschwindigkeiten der Dilatorischen, Rotatorischen und der Oberflächenwellen im elastischen Medium legt fest, welcher der vier möglichen charakteristischen Übergangszustände der Spannungen sich entwickelt.

Jeder der vier Kontaktgeschwindigkeitsbereiche wird mit der Methode der selbst‐ähnlichen Potentiale behandelt.
The Development of Jet Mixing Toward the Asymptotic Similar Solution
Authors: Brink D. F. , Chow W. L.
Published: May 2007

In der Arbeit wird analytisch untersucht, wie sich ein ursprünglich nichtähnliches Geschwindigkeitsprofil bei einem Strahlmischvorgang nach der am Ende asymptotischen ähnlichen Lösung hin entwickelt. Die entsprechenden Gleichungen für die inkompressible Grenzschicht werden mit Hilfe der asymptotischen Integrationsmethode von Meksyn für beide Ströme unterhalb und oberhalb der vorkommenden Stromlinie gelöst. Es wird genau beschrieben und diskutiert, wie sich diese Entwicklung der Strömung zu der schließlichen ähnlichen Lösung unter dem Einfluß der Anfangsbedingung verhält.
Die Beeinflussung der Stabilität von Laminarströmungen durch die Eigenschaften der Wände
Authors: Brechling J.
Published: May 2007

Die Entwicklung von Störbewegungen in einer Laminarströmung kann durch Bewegung der die Strömung begrenzenden Wände weitgehend variiert werden. Im einzelnen untersucht wird das Problem der passiven Beeinflussung, bei der die Wandbewegung durch die Störströmung selbst angeregt wird. Zur Berechnung der Stabilität wird ein geeignetes Rechenverfahren zur Integration der Sommerfeldschen Gleichung als Eigenwertaufgabe entwickelt.
Zur Begründung einiger Iterationsmethoden in der Nichtlinearen Kriechtheorie
Authors: Babadshanjan H.
Published: May 2007

Am Beispiel von Randwertaufgaben der nichtlinearen Kriechtheorie werden die Methode der zusätzlichen Deformationen und die Methode der zusätzlichen Belastungen begründet.
Über die Konstruktion Greenscher Tensoren und ihre Bedeutung für die numerische Mathematik
Authors: Beckert Herbert
Published: May 2007

In dieser Arbeit wurden zu allgemeinen linearen Bandwertproblemen stark elliptischer Systeme die klassischen und erweiterten Greenschen Tensoren mit Variationsmethoden konstruiert und deren Singularitätsordnung am Rande abgeschätzt. Dieselbe Konstruktion ergeben die reduzierten Greenschen Tensoren über endlichdimensionalen Ritzschen Teilräumen 𝔐n. Für die numerische Mathematik ist von Bedeutung, daß für diese Tensoren auch die klassische Darstellungsformel für die Ritz‐Lösung über 𝔐n gültig ist.
Uric acid changes in urine and plasma: An effective tool in screening for purine inborn errors of metabolism and other pathological conditions
Authors: Simoni R. E. , Ferreira Gomes L. N. L. , Scalco F. B. , Oliveira C. P. H. , Aquino Neto F. R. , Costa de Oliveira M. L.
Published: May 2007

Purine inborn errors of metabolism (IEM) are serious hereditary disorders, which should be suspected in any case of neonatal fitting, failure to thrive, recurrent infections, neurological deficit, renal disease, self‐mutilation and other manifestations. Investigation usually starts with uric acid (UA) determination in urine and plasma. UA, the final product of purine metabolism in humans, may be altered not only in purine IEM, but also in other related pathologies and clinical conditions. However, data and information about abnormal UA levels are scattered in the literature, often being controversial and confusing. A comprehensive overview has been elaborated, according to abnormal UA levels in urine and plasma, which associates these alterations with purine IEM. Other possible diseases, clinical conditions, diet and drug intake, related to the metabolism of uric acid, are also presented. The article includes tables that classify the disorders according to different patterns of UA alterations, with pertinent enzymes, clinical symptoms, inheritance and comments. Additionally, summarized pathophysiological mechanisms of important disorders are described. The overview is intended to assist in the interpretation of the results of UA analyses. It demonstrates that variation of UA concentrations in urine and plasma may constitute an effective tool in screening for purine IEM and other related pathological conditions.
Erblicher Brust- und Eierstockkrebs
Authors: Gadzicki D. , Meindl A. , Schlegelberger B.
Published: May 2007

Erbliche Faktoren spielen eine wesentliche Rolle bei der Entstehung des Brustkrebses. Etwa die Hälfte der erblich bedingten Erkrankungen wird auf Veränderungen in den 1994 bzw. 1995 identifizierten Genen BRCA1 und BRCA2 zurückgeführt. BRCA1 und BRCA2 spielen eine wesentliche Rolle in der zellulären Antwort auf DNA-Schäden und sind über die zahlreiche Interaktionspartner an mehreren Signalwegen beteiligt, die u. a. die Zellzykluskontrolle, das „Chromatin-Remodeling“ und den Proteinabbau über die Ubiquitinierung steuern. Der Nachweis einer BRCA1/2-Mutation hat erhebliche Implikationen für das Risiko, (erneut) an Brust- und Eierstockkrebs zu erkranken. Die Entwicklung zielgerichteter Therapieoptionen wird es in Zukunft unentbehrlich machen, bereits zum Zeitpunkt der Diagnosestellung zu wissen oder so schnell wie möglich zu ermitteln, ob eine BRCA1/2-Mutation vorliegt, um wirkungsvolle operative oder therapeutische Maßnahmen zu ergreifen.
Psychotropic drugs use and risk of heat-related hospitalisation
Authors: Martin-Latry Karin , Goumy Marie-Pierre , Latry Philippe , Gabinski Claude , Bégaud Bernard , Faure Isabelle , Verdoux Hélène
Published: May 2007

Objective

To assess if use of psychotropic drugs is associated with an increased risk of admission for heat-related pathologies during a heat wave period.

Method

We conducted a matched case–control study. Cases were defined as subjects admitted to an emergency department for heat-related pathology (hyperthermia or heat stroke) over the August 2003 heat wave. Controls were defined as subjects living in the same area but not hospitalised over the same period and who had at least one prescription form submitted for refunding by the social security insurance in July 2003. Multivariate analyses were used to identify psychotropic drugs independently associated with hospital referral during the heat wave period.

Results

Out of the 1405 patients admitted to the emergency department, 56 (4%) presented with heat-related pathology. The mean age of cases was 83 years. Multivariate analyses showed that cases were more likely than controls to be treated with anticholinergic drugs (OR 6.0, 95% CI 1.8–19.6), antipsychotics (OR 4.6, 95% CI 1.9–11.2) or anxiolytics (OR 2.4, 95% CI 1.3–4.4).

Conclusion

In special risk situations such as heat waves, the risk/benefit ratio of psychotropic drugs which could interfere with body temperature regulation has to be carefully assessed, particularly in the elderly.
Coupled positive feedbacks provoke slow induction plus fast switching in apoptosis
Authors: Choi Hyung-Seok , Han Soohee , Yokota Hiroki , Cho Kwang-Hyun
Published: May 2007

Apoptosis is a form of a programmed cell death for multicellular organisms to remove unwanted or damaged cells. This critical choice of cellular fate is an all‐or‐none process, but its dynamics remains unraveled. The switch‐like apoptotic decision has to be reliable, and once a pro‐apoptotic fate is determined it requires fast and irreversible execution. One of the key regulators in apoptosis is caspase‐3. Interestingly, activated caspase‐3 quickly executes apoptosis, but it takes considerable time to activate it. Here, we have analyzed this “slow induction plus fast switching” mechanism of caspase‐3 through mathematical modeling and computational simulation. First, we have shown that two positive feedbacks, composed of caspase‐8 and XIAP, are essential for the “slow induction plus fast switching” behavior of caspase‐3. Second, we have found that XIAP in the feedback loops primarily regulates induction time of caspase‐3. In many cancer cells activation of caspase‐3 is suppressed. Our results suggest that reinforcement of the positive feedback by XIAP, which relieves XIAP‐mediated caspase‐3 inhibition, might favor a pro‐apoptotic cellular fate.
Collagen matrix deposition is dramatically enhanced in vitro when crowded with charged macromolecules: The biological relevance of the excluded volume effect
Authors: Lareu Ricky R. , Subramhanya Karthik Harve , Peng Yanxian , Benny Paula , Chen Clarice , Wang Zhibo , Rajagopalan Raj , Raghunath Michael
Published: May 2007

The excluded volume effect (EVE) rules all life processes. It is created by macromolecules that occupy a given volume thereby confining other molecules to the remaining space with large consequences on reaction kinetics and molecular assembly. Implementing EVE in fibroblast culture accelerated conversion of procollagen to collagen by procollagen C‐proteinase (PCP/BMP‐1) and proteolytic modification of its allosteric regulator, PCOLCE1. This led to a 20–30‐ and 3–6‐fold increased collagen deposition in two‐ and three‐dimensional cultures, respectively, and creation of crosslinked collagen footprints beneath cells. Important parameters correlating with accelerated deposition were hydrodynamic radius of macromolecules and their negative charge density.
mRNA quality control: An ancient machinery recognizes and degrades mRNAs with nonsense codons
Authors: Behm-Ansmant Isabelle , Kashima Isao , Rehwinkel Jan , Saulière Jérôme , Wittkopp Nadine , Izaurralde Elisa
Published: May 2007

Nonsense‐mediated mRNA decay (NMD) is an mRNA surveillance pathway which ensures the rapid degradation of mRNAs containing premature translation termination codons (PTCs or nonsense codons), thereby preventing the accumulation of truncated and potentially harmful proteins. In this way, the NMD pathway contributes to suppressing or exacerbating the clinical manifestations of specific human genetic disorders. Studies in model organisms have led to the identification of the effectors of the NMD pathway, and illuminated the mechanisms by which premature stops are discriminated from natural stops, so that only the former trigger rapid mRNA degradation. These studies are providing important insights that will aid the development of new treatments for at least some human genetic diseases.
Automated cryoelectron microscopy of “single particles” applied to the 26S proteasome
Authors: Nickell Stephan , Beck Florian , Korinek Andreas , Mihalache Oana , Baumeister Wolfgang , Plitzko Jürgen M.
Published: May 2007

The 26S proteasome is a large molecular machine with a central role in intracellular protein degradation in eukaryotes. The 2.5 MDa complex, which is built from two copies each of more than 30 different subunits, is labile and prone to dissociation into subcomplexes. Hence it is difficult if not impossible, to obtain structurally homogeneous preparations and, as a consequence, it is very cumbersome to obtain large numbers of images of the holocomplex. In this communication, we describe an automated procedure for the acquisition of large data sets of cryoelectron micrographs. The application of this procedure to the 26S proteasome from Drosophila has allowed us to determine the three‐dimensional structure of the complex to a resolution of 2.9 nm and the prospects for further improvements are good.
Treating IBD: A Patient's Guide to the Medical and Surgical Management of Inflammatory Bowel Disease
Authors: Pawlowski Jacqueline
Published: May 2007

Treating IBD: A Patient's Guide to the Medical and Surgical Management of Inflammatory Bowel Disease Edited by Lawrence J. Brandt, Penny Steiner‐Grossman 1989, 201 pp $15 paperback
Surgical Nursing
Authors: Persson June C.
Published: May 2007

Surgical Nursing By Mary Jane Evans, Mary Ann Black 1990, 195 pp $11.95 paperback
First Words: Selected Addresses from the National League for Nursing 1894–1933
Authors: Guinn N. Joanne
Published: May 2007

First Words: Selected Addresses from the National League for Nursing 1894–1933 Edited by Nettie Birnbach, Sandra Lewenson 1991, 375 pp $34.95 paperback
Director Liability: A Guide to Preventing Trouble in the Hospital Boardroom
Authors: Koch Frances A.
Published: May 2007

Director Liability: A Guide to Preventing Trouble in the Hospital Boardroom By Robert J. Burdett, Jr 1991, 132 pp $25.95 AHA members, $32.95 nonmembers paperback
Understanding Pharmacology
Authors: Garrett Caroline K.
Published: May 2007

Understanding Pharmacology By Susan M. Turley 1991, 228 pp $24 spiral bound
Perceived stressors and coping responses in persons with recurrent genital herpes
Authors: Keller ML , Jadack RA , Mims LF , Moss Vicki A. ,   Nursing Research Committee
Published: May 2007

Perceived stressors and coping responses in persons with recurrent genital herpes, M L Keller, R A Jadack, L F Mims Research in Nirrsing and Health Vol 14 (December 1991) 42 1–430
Microbial and dietary factors associated with the 8-prenylnaringenin producer phenotype: a dietary intervention trial with fifty healthy post-menopausal Caucasian women
Authors: Bolca Selin , Possemiers Sam , Maervoet Veerle , Huybrechts Inge , Heyerick Arne , Vervarcke Stefaan , Depypere Herman , De Keukeleire Denis , Bracke Marc , De Henauw Stefaan , Verstraete Willy , Van de Wiele Tom
Published: May 2007

Hop-derived food supplements and beers contain the prenylflavonoids xanthohumol (X), isoxanthohumol (IX) and the very potent phyto-oestrogen (plant-derived oestrogen mimic) 8-prenylnaringenin (8-PN). The weakly oestrogenic IX can be bioactivated viaO-demethylation to 8-PN. Since IX usually predominates over 8-PN, human subjects may be exposed to increased doses of 8-PN. A dietary intervention trial with fifty healthy post-menopausal Caucasian women was undertaken. After a 4 d washout period, participants delivered faeces, blank urine and breath samples. Next, they started a 5 d treatment with hop-based supplements that were administered three times per d and on the last day, a 24 h urine sample was collected. A semi-quantitative FFQ was used to estimate fat, fibre, alcohol, caffeine and theobromine intakes. The recoveries of IX, 8-PN and X in the urine were low and considerable inter-individual variations were observed. A five-fold increase in the dosage of IX without change in 8-PN concentration resulted in a significant lower IX recovery and a higher 8-PN recovery. Classification of the subjects into poor (60 %), moderate (25 %) and strong (15 %) 8-PN producers based on either urinary excretion or microbial bioactivation capacity gave comparable results. Recent antibiotic therapy seemed to affect the 8-PN production negatively. A positive trend between methane excretion and 8-PN production was observed. Strong 8-PN producers consumed less alcohol and had a higher theobromine intake. From this study we conclude thatin vivoO-demethylation of IX increases the oestrogenic potency of hop-derived products.
Evaluation of linkage disequilibrium measures between multi-allelic markers as predictors of linkage disequilibrium between single nucleotide polymorphisms
Authors: ZHAO H. , NETTLETON D. , DEKKERS J. C. M.
Published: May 2007

Effectiveness of marker-assisted selection (MAS) and quantitative trait locus (QTL) mapping using population-wide linkage disequilibrium (LD) between markers and QTLs depends on the extent of LD and how it declines with distance between markers and QTLs in a population. Marker–QTL LD can be predicted from LD between markers. Our previous work evaluated LD measures between multi-allelic markers as predictors of usable LD of multi-allelic markers with QTLs. Since single nucleotide polymorphisms (SNPs) are the current marker of choice for high-density genotyping and LD-mapping of QTLs, the objective of this study was to use LD between multi-allelic markers to predict LD among biallelic SNPs or between SNPs and QTLs. Observable LD between multi-allelic markers was evaluated using nine measures. These included two pooled and standardized measures of LD between pairs of alleles at two markers based on Lewontin's LD measure, two pooled measures of squared correlations between alleles, one standardized measure using Hardy–Weinberg heterozygosities, and four measures based on the chi-square statistic for testing for association between alleles at two loci. The standardized chi-square measure that best predicted usable LD between multi-allelic markers and QTLs, based on our previous work, overestimated usable SNP–SNP or SNP–QTL LD. Instead, three other measures were found to be good predictors of usable SNP–SNP or SNP–QTL LD when LD is generated by drift. Therefore, the LD measure between multi-allelic markers that is best for predicting usable LD in a population depends on the type of markers (i.e. multi-allelic or biallelic) that will eventually be used for QTL mapping or MAS.
A structural mixed model for variances in differential gene expression studies
Authors: JAFFRÉZIC FLORENCE , MAROT GUILLEMETTE , DEGRELLE SÉVERINE , HUE ISABELLE , FOULLEY JEAN-LOUIS
Published: May 2007

The importance of variance modelling is now widely known for the analysis of microarray data. In particular the power and accuracy of statistical tests for differential gene expressions are highly dependent on variance modelling. The aim of this paper is to use a structural model on the variances, which includes a condition effect and a random gene effect, and to propose a simple estimation procedure for these parameters by working on the empirical variances. The proposed variance model was compared with various methods on both real and simulated data. It proved to be more powerful than the gene-by-gene analysis and more robust to the number of false positives than the homogeneous variance model. It performed well compared with recently proposed approaches such as SAM and VarMixt even for a small number of replicates, and performed similarly to Limma. The main advantage of the structural model is that, thanks to the use of a linear mixed model on the logarithm of the variances, various factors of variation can easily be incorporated in the model, which is not the case for previously proposed empirical Bayes methods. It is also very fast to compute and is adapted to the comparison of more than two conditions.
Small-world networks decrease the speed of Muller's ratchet
Authors: COMBADÃO JAIME , CAMPOS PAULO R. A. , DIONISIO FRANCISCO , GORDO ISABEL
Published: May 2007

Muller's ratchet is an evolutionary process that has been implicated in the extinction of asexual species, the evolution of non-recombining genomes, such as the mitochondria, the degeneration of the Y chromosome, and the evolution of sex and recombination. Here we study the speed of Muller's ratchet in a spatially structured population which is subdivided into many small populations (demes) connected by migration, and distributed on a graph. We studied different types of networks: regular networks (similar to the stepping-stone model), small-world networks and completely random graphs. We show that at the onset of the small-world network – which is characterized by high local connectivity among the demes but low average path length – the speed of the ratchet starts to decrease dramatically. This result is independent of the number of demes considered, but is more pronounced the larger the network and the stronger the deleterious effect of mutations. Furthermore, although the ratchet slows down with increasing migration between demes, the observed decrease in speed is smaller in the stepping-stone model than in small-world networks. As migration rate increases, the structured populations approach, but never reach, the result in the corresponding panmictic population with the same number of individuals. Since small-world networks have been shown to describe well the real contact networks among people, we discuss our results in the light of the evolution of microbes and disease epidemics.
Shipping of water on a two-dimensional structure. Part 2
Authors: GRECO M. , COLICCHIO G. , FALTINSEN O. M.
Published: May 2007

The water-shipping problem is modelled in a two-dimensional framework and studied experimentally and numerically for the case of a fixed barge-shaped structure. The analysis represents the second step of the research discussed in Grecoet al. (J. Fluid Mech., vol. 525, 2005, p. 309). The numerical investigation is performed by using both a boundary element method and a domain-decomposition strategy. The model tests highlight the occurrence of dam-breaking-type water on deck, (a) with and (b) without an initial plunging phase, and (c) an unusual type of water shipping connected with blunt water–deck impacts here called a hammer-fist type event never documented before. Cases (a) and (c) are connected with the most severe events and the related features and green-water loads are discussed in detail. A parametric analysis of water-on-deck phenomena has also been carried out in terms of the local incoming waves and bow flow features. We classify such phenomena in a systematic way to provide a basis for further investigations of water-on-deck events. The severity of (a)-type water-on-deck events is analysed in terms of initial cavity area and water-front velocity along the deck. The former increases as the square power of the modified incoming-wave (front-crest) steepness while the latter scales with its square-root. The two-dimensional investigation gives useful quantitative information in terms of water-front velocity for comparison with three-dimensional water-on-deck experiments on fixed bow models interacting with wave packets.
Axisymmetric liquid-metal pipe flow through a non-uniform magnetic field containing a neutral point
Authors: KENNY RICHARD G.
Published: May 2007

Axisymmetric liquid-metal pipe flow passes through a quadrupole magnetic field that is generated by a pair of ‘oppositely sensed’ d.c. current coils. As a result of this arrangement, the flow experiences a degree of braking, mostly in the vicinity of the magnetic neutral point, owing to the effect of Lorentz forces acting upon the liquid-metal. Usefully, the system represents a practical and novel electromagnetic (e.m.) valve capable of regulating the flow of molten metal emanating from a tun-dish, for example. Linear theory predicts the development of a counter-intuitive unidirectional ‘slug-like’ profile throughout the liquid-metal pipe flow at large values of the Hartmann number, M, in the presence of an idealized axisymmetric neutral point that extends to infinity. We confirm that this behaviour is also apparent, but over a narrow region spanning the neutral point, in the case of a more realistic liquid-metal pipe flow acted upon by a pair of oppositely sensed d.c. current coils. The axial pressure gradient along the wall of this flow manifests a sharp peak at large M centred on the neutral point that is generated by the steep gradients in the slug profile there. In fact, the pressure drop developed across this region is approximately equal to the net braking effect of the e.m. valve.