Coexistence of Service- and Facility-Based Competition: The Relevance of Access Prices for "Make-or-Buy"-Decisions

This paper models competition between two firms, which provide broadband Internet access in regional markets with different population densities. The firms, an incumbent and an entrant, differ in two ways. First, consumers bear costs when switching to the entrant. Second, the entrant faces a make-or-buy decision in each region and can choose between service-based and facility-based entry. The usual trade-off between static and dynamic eficiency does not apply in the sense that higher access fees might yield both, lower retail prices and higher total coverage. This holds despite a strategic effect in the entrant's investment decision. While investment lowers marginal costs in regions with facility-based entry, it intensifies competition in all regions. We show that the cost-reducing potential of investments dominates the strategic effect: Higher access fees increase facility-based competition, decrease retail prices and increase total demand.Broadband access markets, facility- and service-based entry, investments, economies of density, switching costs

Coexistence of service- and facility-based competition: The relevance of access prices for "make-or-buy"-decisions

This paper models competition between two firms, which provide broadband Internet access in regional markets with different population densities. The firms, an incumbent and an entrant, differ in two ways. First, consumers bear costs when switching to the entrant. Second, the entrant faces a make-or-buy decision in each region and can choose between service-based and facility-based entry. The usual trade-off between static and dynamic efficiency does not apply in the sense that higher access fees might yield both, lower retail prices and higher total coverage. This holds despite a strategic effect in the entrant's investment decision. While investment lowers marginal costs in regions with facility-based entry, it intensifies competition in all regions. We show that the cost-reducing potential of investments dominates the strategic effect: Higher access fees increase facility-based competition, decrease retail prices and increase total demand. --Broadband access markets,facility- and service-based entry,investments,economies of density,switching costs

High Order Perturbation Theory for Spectral Densities of Multi-Particle Excitations: S=1/2 Two-Leg Heisenberg Ladder

We present a high order perturbation approach to quantitatively calculate spectral densities in three distinct steps starting from the model Hamiltonian and the observables of interest. The approach is based on the perturbative continuous unitary transformation introduced previously. It is conceived to work particularly well in models allowing a clear identification of the elementary excitations above the ground state. These are then viewed as quasi-particles above the vacuum. The article focuses on the technical aspects and includes a discussion of series extrapolation schemes. The strength of the method is demonstrated for S=1/2 two-leg Heisenberg ladders, for which results are presented.Comment: 21 pages, 14 figures included; to appear in Eur. Phys. J. B All technical details for the computation of spectral densities by perturbative CUTs Minor misprints removed, references update

Economic incentives of the WTO dispute settlement system with an empirical focus on the agro-food sector

The thesis contributes to the understanding of the drivers in countries’ decision to adjudicate trade issues under the Dispute Settlement Mechanism (DSM) of the World Trade Organization (WTO). The DSM is a rules-based device for the resolution of conflicts arising over the interpretation of trade law under the regime of the organization. The DSM is self-enforcing, i.e. all actions of disputes are driven by the parties to the dispute. This Member-driven nature of the DSM implies that the conditions of its use are determined by market-related incentives, Members’ resource endowments and constraints, and the characteristics of the political economic relationship between potential complainants and defendants. Negotiations on improvements of the DSM are going on since 1997 without yielding any resolution so far. The negotiations aim at making the DSM more effective and to allow for equal accessibility of the system to all types of Members. Reform proposals span a broad field; however, a targeted improvement of the system requires a thorough understanding of economic incentives and constraints faced by the potential users of the system. Apart from an introduction, the thesis comprises two empirical and a theoretical chapter. The empirical parts are focused on the agro-food sector to provide a more in-depth analysis of sector-related characteristics. The starting point is an aggregated analysis on capacity- and sector-related traits of initiating Members and is based on a Binomial dispute distribution model adapted from the literature. The second empirical chapter builds upon the analysis of the first but shifts the focus to bilaterally dependent characteristics, which are of essential relevance for the enforcement of compliance. The empirical intricacy implied by the pure bilateral approach is solved by the application of the Weighted Endogenous Sampling Maximum Likelihood (WESML) estimator. Results show that Members’ tendency toward protectionist policies decrease and the level of protectionism faced in their exports increase their probability to initiate disputes. The first finding suggests a strategic behavior and may also reflect Members’ general tendency towards market liberalization. The second finding is in line with the system’s objectives. Also, Members’ operating experience shows a positive effect on their number of filed disputes. This can be rationalized by decreased fixed costs of litigation and by gained efficiency in the processing of disputes through experience. In addition, the positive influence of lobbying activity, their dependency on the defendant’s market for exports and the value of agro-food imports from the defendant country could be supported. The empirical investigations are complemented by a theory paper. Drawing on the findings mentioned above and those from previous empirical investigations on WTO dispute settlement, the chapter develops a comprehensive economic modeling framework for the initiation of disputes. It thereby may serve as a tool for the evaluation of the system’s status quo and the assessment of envisaged system changes.Die ökonomischen Anreize des WTO Streitschlichtungsverfahrens mit emprischem Schwerpunkt auf dem Agrar- und Lebensmittelsektor Die Dissertation leistet einen Beitrag zum Verständnis der Einflussfaktoren in der Entscheidung von Ländern, ihre Handelsauseinandersetzungen im Rahmen des Streitschlichtungsmechanismus (SSM) der Welthandelsorganisation (WTO) zu verhandeln. Der SSM is eine regelbasierte Institutiton für die Lösung von Konflikten über die Interpretation des Handelsrechts unter dem Geltungsbereich der Organisation. Es handelt sich dabei um ein selbstgesteuertes Verfahren, d.h. dass alle damit verbundenen Aktivitäten von den Streitparteien getragen werden. Diese mitgliedergetriebene Eigenschaft des SSM beinhaltet, dass seine Nutzungsbedingungen bestimmt werden durch marktbezogene Anreize, durch die Ressourcenausstattung der Mitglieder der Organisation und durch die Beschaffenheit der politikökonomischen Beziehung zwischen potentiellen Klägern und Beklagten. Über eine Verbesserung des SSM wird seit 1997 verhandelt, ohne dass es bislang zu einer Lösung gekommen wäre. Die Verhandlungen zielen darauf ab, die Effektivität des SSM zu erhöhen und seine Nutzbarkeit allen Arten von Mitgliedern zu ermöglichen. Die Reformvorschläge sind breit gefächert. Jedoch erfordert eine gezielte Verbesserung des Systems ein tiefgründiges Verständnis der ökonomischen Anreize und der Einschränkungen, denen potentielle Nutzer des Systems gegenüberstehen. Zusätzlich zu einer umfangreicheren Einleitung umfasst die Dissertation zwei empirische und ein theoretisches Kapitel. Die empirischen Teile sind auf den Agrar- und Lebensmittelsektor fokussiert, um eine eingehendere Untersuchung der sektorbezogenen Eigenschaften bereitzustellen. Der Ausgangspunkt ist eine aggregierte Analyse von kapazitäts- und sektorbezogenen Charakteristiken von Klägern, und hat als Grundlage ein Binomiales Verteilungsmodell für Streitfälle, welches aus der Literatur entnommen wurde. Das zweite empirische Kapitel baut auf dieser ersten Analyse auf, verschiebt den Fokus jedoch hin zu bilateral abhängigen Ländereigenschaften, welche von entscheidener Bedeutung für die Durchsetzung der Regeleinhaltung sind. Die mit dem bilateralen Ansatz verbundene empirische Komplexität wird durch die Anwendung des Weighted Endogenous Sampling Maximum Likelihood (WESML)-Schätzers gelöst. Die Ergebnisse zeigen, dass die protektionistische Tendenz von WTO-Mitgliedern ihre Klagewahrscheinlichkeit verringert und der Umfang protektionistischer Politiken, welchen sie in ihren Exportströmen ausgesetzt sind, ihre Klagewahrscheinlichkeit erhöt. Ersteres mag ein strategisches Verhalten der Länder oder auch ihre generelle Einstellung im Hinblick auf Handelsliberalisierung widerspiegeln. Letzteres befindet sich in Übereinstimmung mit den Zielen des Systems. Die Anwendungserfahrung mit dem System zeigt ebenfalls einen positiven Einfluss auf die Anzahl von Klagen. Dies kann erklärt werden mit abnehmenden Fixkosten und zunehmender Effizienz in der Bearbeitung von Streitfällen durch die gewonnene Erfahrung. Zusätzlich zeigen Lobbyaktivität, die Relevanz des beklagten Marktes für Exporte und der Wert von Agrar- und Lebensmittelimporten von diesem einen positiven Effekt auf die Klagewahrscheinlichkeit von Ländern. Die empirischen Analysen werden durch ein theoretisches Kapitel ergänzt. Indem es sich auf die oben zitierten Ergebnisse sowie auf diejenigen vorhergehender empirischer Untersuchungen zum WTO-Streitschlichtungssystem stützt, entwickelt das Theoriekapitel ein umfassendes ökonomisches Modell für die Initiierung von Streitfällen. Es mag daher als Mittel zur Evaluierung des status quo des SSM, wie auch zur Bewertung der anvisierten Änderungen des Systems dienen

On the Use of Formative Measurement Specifications in Structural Equation Modeling: A Monte Carlo Simulation Study to Compare Covariance-Based and Partial Least Squares Model Estimation Methodologies

The broader goal of this paper is to provide social researchers with some analytical guidelines when investigating structural equation models (SEM) with predominantly a formative specification. This research is the first to investigate the robustness and precision of parameter estimates of a formative SEM specification. Two distinctive scenarios (normal and non-normal data scenarios) are compared with the aid of a Monte Carlo simulation study for various covariance-based structural equation modeling (CBSEM) estimators and various partial least squares path modeling (PLS-PM) weighting schemes. Thus, this research is also one of the first to compare CBSEM and PLS-PM within the same simulation study. We establish that the maximum likelihood (ML) covariance-based discrepancy function provides accurate and robust parameter estimates for the formative SEM model under investigation when the methodological assumptions are met (e.g., adequate sample size, distributional assumptions, etc.). Under these conditions, ML-CBSEM outperforms PLS-PM. We also demonstrate that the accuracy and robustness of CBSEM decreases considerably when methodological requirements are violated, whereas PLS-PM results remain comparatively robust, e.g. irrespective of the data distribution. These findings are important for researchers and practitioners when having to choose between CBSEM and PLS-PM methodologies to estimate formative SEM in their particular research situation.PLS, path modeling, covariance structure analysis, structural equation modeling, formative measurement, simulation study

On the Use of Formative Measurement Specifications in Structural Equation Modeling: A Monte Carlo Simulation Study to Compare Covariance-Based and Partial Least Squares Model Estimation Methodologies

The broader goal of this paper is to provide social researchers with some analytical guidelines when investigating structural equation models (SEM) with predominantly a formative specification. This research is the first to investigate the robustness and precision of parameter estimates of a formative SEM specification. Two distinctive scenarios (normal and non-normal data scenarios) are compared with the aid of a Monte Carlo simulation study for various covariance-based structural equation modeling (CBSEM) estimators and various partial least squares path modeling (PLS-PM) weighting schemes. Thus, this research is also one of the first to compare CBSEM and PLS-PM within the same simulation study. We establish that the maximum likelihood (ML) covariance-based discrepancy function provides accurate and robust parameter estimates for the formative SEM model under investigation when the methodological assumptions are met (e.g., adequate sample size, distributional assumptions, etc.). Under these conditions, ML-CBSEM outperforms PLS-PM. We also demonstrate that the accuracy and robustness of CBSEM decreases considerably when methodological requirements are violated, whereas PLS-PM results remain comparatively robust, e.g. irrespective of the data distribution. These findings are important for researchers and practitioners when having to choose between CBSEM and PLS-PM methodologies to estimate formative SEM in their particular research situation.marketing ;

Contemporary and Past Perspectives

Boundaries are a complex topic, with different categories being distinguishable depending on the language and with a number of terms often used interchangeably. This discussion paper offers an overview on definitions and introduces different types of boundaries such as geographic, political and social. Drawing on disciplines as varied as border studies, international relations, post-/decolonial thought, and on examples from anthropological fieldwork, insights can be derived for archaeological approaches. In this context, the role of boundaries in the dynamic construction of ethnic identities is highlighted. A discussion of ancient Egyptian terms and concepts of political boundaries underlines the comparative potential of studies in premodern political thought and lived experience

Expanding the Scope of Impedance Spectroscopy for the Analysis of Adherent Cells: Electrode Material, Electrode Design, and Data Analysis

This thesis focused on the advancement of impedance-based cellular assays using the electric cell-substrate impedance sensing (ECIS) approach. Three linchpins of ECIS were addressed: electrode material, electrode design, and data analysis. Typically, ECIS measurements are performed by application of ac currents with low amplitude between coplanar gold-film electrodes with adherent cell monolayers growing on top. Different chapters of this work discussed the replacement of the electrode material gold by a conducting polymer, the use of a single bipolar electrode instead of two separate electrodes, and the data analysis by means of the derivatives of impedance spectra. The first part of this work dealt with the fabrication and characterization of screen printed polymer electrode arrays. The arrays, called PDT, were based on the conducting polymer PEDOT:PSS as electrode material, silver leads to reduce the lead resistance, and a silicone passivation layer to delineate the electrode dimensions. The electrodes showed high adhesion stability in aqueous environment at 37 °C, electrical stability in the analytically relevant voltage range between 10 mV and 300 mV, and long-term stability when stored in ambient air in the dark. In comparison with gold electrodes, PEDOT:PSS exhibited a greatly enhanced interface capacitance due to its hydrogel properties. This improved the sensitivity of the impedance magnitude |Z| and the real component of the impedance R at lower frequencies for cell analysis, which is relevant for the analysis of the barrier function and the cell-substrate interaction of adherent cell monolayers. Cell proliferation and adhesion assays are commonly conducted by monitoring the capacitance at 32 kHz or 40 kHz. In this frequency range, the sensitivity of the polymer electrodes surpassed the gold electrodes. A disadvantage of PEDOT:PSS was its high resistivity and thus the high lead resistance, reducing the sensitivities for the parameters |Z| and R at higher frequencies. Alterations in the cell-substrate contact as well as the adhesion and spreading kinetics compared to commercial gold electrodes were discussed with respect to the lower substrate stiffness of PEDOT:PSS compared to gold. Several common analytical assays investigating the micromotion, proliferation, cytotoxicity, and electroporation performance of the PEDOT:PSS electrodes were successfully conducted on both electrode materials, yielding overall similar results. Nevertheless, several differences were established. Due to the high interface capacitance, the PEDOT:PSS electrodes showed an extremely low noise level during micromotion experiments compared to the gold electrodes. This resulted in accordingly high signal-to-noise ratio and sensitivity. The proliferation assay provided more data scattering on PEDOT:PSS electrodes, which could be either attributed to the smaller electrode size or an inhomogeneous distribution of the substrate stiffness across the electrode surface. Due to a reduced generation of cytotoxic species at the electrode surface, the electroporation at lower frequencies (1.5 kHz) was found to be less invasive on PDT electrodes. Different cell lines with individual cell parameters were shown to retain their specific characteristics concerning barrier function, cell-substrate contact, and membrane capacitance on PEDOT:PSS. A remaining challenge is the electrode drift that occurred over the course of several days during the measurement. The drift was less pronounced in the impedance magnitude and appeared more prominently in the capacitance. In the second part of this work, a novel bipolar electrode for impedimetric analysis and manipulation of living cells was developed. The bipolar electrode consisted of a high-resistance conduction path showing a potential gradient along its length. The potential at the respective position on the electrode surface depended on its distance from the contact pads. Thus, upon application of elevated electric fields of 5 V for 60 s, the bipolar electrodes caused a gradient of increasing electric field strength along the conduction path. This property of the bipolar electrodes was explained by an increasing lead resistance with growing distance from the contact pads. The system is suggested to be suitable for the optimization of wounding and electroporation experiments as the position on the electrode indicates the optimal voltage amplitude required for the respective application. In a second approach, bipolar electrodes were fabricated comprising a passivation layer with a small working and a large counter electrode like in the ECIS layout. For this layout, a mathematical model based on the ECIS model was developed. Using this model, it was shown that the low frequency part of the impedance magnitude spectrum was determined by the inherent resistance of the bipolar electrode. Compared to ECIS electrodes, the bipolar electrodes showed a sensitivity shift from the real part to the imaginary part of the complex impedance. The third part of this work aimed to improve the accuracy of data analysis for impedance spectroscopy by calculating the derivatives of the spectra. Therefore, a set of methods was developed to analyze the applicability of derivative impedance spectroscopy (DIS) for the analysis of impedance-based cellular assays. Artificial raw data with known electrode and cell parameters were created by overlaying simulated impedance spectra with computer-generated noise. The derivative orders zero to three of these spectra were fitted using different settings of the fitting conditions and weighting methods. For a quantitative evaluation, the parameter Qrel was introduced, which is a direct measure for the quality of a fit. For certain fitting conditions the first derivative displayed some improvement compared to the zero-order spectrum. However, the overall tendency was a strong decline of the fit quality with increasing derivative order. This was found to be due to insufficient reduction of the noise, which is amplified after each differentiation. In a second approach, DIS was used to discriminate between spectral changes caused by alterations of either one of the cell parameters, α or Rb. Fixed frequencies were found, where simulations showed more distinct differences in the first or second derivative than in the zero-order spectrum. In particular, the first and second derivative exhibited opposing tendencies for the two cell parameters at 400 Hz and 1 kHz, respectively. Moreover, the migration of the zero-points of the second derivative when varying the cell parameters might become useful in a similar fashion. The high-frequency zero-point (~ 10 kHz) was shown to migrate only upon alteration of Rb and was unaffected by α. The results presented in this chapter are only valid for the investigated system and are not applicable to other cell lines