Orthogonal Graph Drawing with Inflexible Edges

We consider the problem of creating plane orthogonal drawings of 4-planar graphs (planar graphs with maximum degree 4) with constraints on the number of bends per edge. More precisely, we have a flexibility function assigning to each edge $e$ a natural number $\mathrm{flex}(e)$, its flexibility. The problem FlexDraw asks whether there exists an orthogonal drawing such that each edge $e$ has at most $\mathrm{flex}(e)$ bends. It is known that FlexDraw is NP-hard if $\mathrm{flex}(e) = 0$ for every edge $e$. On the other hand, FlexDraw can be solved efficiently if $\mathrm{flex}(e) \ge 1$ and is trivial if $\mathrm{flex}(e) \ge 2$ for every edge $e$. To close the gap between the NP-hardness for $\mathrm{flex}(e) = 0$ and the efficient algorithm for $\mathrm{flex}(e) \ge 1$, we investigate the computational complexity of FlexDraw in case only few edges are inflexible (i.e., have flexibility~$0$). We show that for any $\varepsilon > 0$ FlexDraw is NP-complete for instances with $O(n^\varepsilon)$ inflexible edges with pairwise distance $\Omega(n^{1-\varepsilon})$ (including the case where they induce a matching). On the other hand, we give an FPT-algorithm with running time $O(2^k\cdot n \cdot T_{\mathrm{flow}}(n))$, where $T_{\mathrm{flow}}(n)$ is the time necessary to compute a maximum flow in a planar flow network with multiple sources and sinks, and $k$ is the number of inflexible edges having at least one endpoint of degree 4.Comment: 23 pages, 5 figure

Entrepreneurial Human Capital, Complementary Assets, and Takeover Probability

Gaining access to technologies, competencies, and knowledge is observed as one of the major motives for corporate mergers and acquisitions. In this paper we show that a knowledge-based firm’s probability of being a takeover target is influenced by whether relevant specific human capital aimed for in acquisitions is directly accumulated within a specific firm or is bound to its founder or manager owner. We analyze the incentive effects of different arrangements of ownership in a firm’s assets in the spirit of the Grossman-Hart-Moore incomplete contracts theory of the firm. This approach highlights the organizational significance of ownership of complementary assets. In a small theoretical model we assume that the entrepreneur’s specific human capital, as measured by the patents they own, and the physical assets of their firm are productive only when used together. Our results show that it is not worthwhile for an acquirer to purchase the alienable assets of this firm due to weakened incentives for the initial owner. Regression analysis using a hand collected dataset of all German IPOs in the period from 1997 to 2006 subsequently provides empirical support for this prediction. This paper adds to previous research in that it puts empirical evidence to the Grossman-Hart-Moore framework of incomplete contracts or property rights respectively. Secondly, we show that relevant specific human capital that is accumulated by a firm’s founder or manager owner significantly decreases that firm’s probability of being a takeover target.ownership structure, property rights, mergers & acquisitions

Competitiveness – A Comparison of China and Mexico

Latin American countries have lost competitiveness in world markets in comparison to China over the last two decades. The main purpose of this study is to examine the causes of this development. To this end an augmented Ricardian model is estimated using panel data. The explanatory variables considered are productivity, unit labor costs, unit values, trade costs, price levels (in PPP), and real exchange rates in relative terms. Due to data restrictions, China’s relative exports (to the US, Argentina, Japan, Korea, UK, Germany, and Spain) will be compared to Mexico’s exports for a number of sectors over a period of eleven years. Panel and pooled estimation techniques (SUR-estimation, panel Feasible Generalized Least Squares (panel/pooled FGLS)) will be utilized to better control for country-specific effects (differences between American, Argentinian, Japanese, Korean, German, British, and Spanish markets), cross-section specific (sector-specific) effects, and correlation over time.Ricardian model of trade, panel data models, panel Feasible Generalized Least Squares, Seemingly Unrelated (SUR) estimation

On Distributed Lags in Dynamic Panel Data Models: Evidence from Market Shares

The objective of this paper is twofold: First, the applicability of a widely used dynamic model, the autoregressive distributed lag model (ARDL), is scrutinized in a panel data setting. Second, Chile’s development of market shares in the EU market in the period of 1988 to 2002 is then analyzed in this dynamic framework, testing for the impact of price competitiveness on market shares and searching for estimation methods that deal with the problem of intertemporal and cross-section correlation of the disturbances. To estimate the coefficients of the ARDL model, Feasible Generalized Least Squares (FGLS) is utilized within the Three Stage Least Squares (3SFGLS) and the system Generalized Method of Moments (system GMM) frameworks. A computation of errors is added to highlight the usceptibility of the model to problems related to the underlying model assumptions.dynamic panel data model, autoregressive distributed lag model; pooled 3Stage Feasible Generalized Least Squares estimation, panel GMM estimation, market shares

Electron-hole interactions in coupled InAs-GaSb quantum dots based on nanowire crystal phase templates

We report growth and characterization of a coupled quantum dot structure that utilizes nanowire templates for selective epitaxy of radial heterostructures. The starting point is a zinc blende InAs nanowire with thin segments of wurtzite structure. These segments have dual roles: they act as tunnel barriers for electron transport in the InAs core, and they also locally suppress growth of a GaSb shell, resulting in coaxial InAs-GaSb quantum dots with integrated electrical probes. The parallel quantum dot structure hosts spatially separated electrons and holes that interact due to the type-II broken gap of InAs-GaSb heterojunctions. The Coulomb blockade in the electron and hole transport is studied, and periodic interactions of electrons and holes are observed and can be reproduced by modeling. Distorted Coulomb diamonds indicate voltage-induced ground-state transitions, possibly a result of changes in the spatial distribution of holes in the thin GaSb shell.Comment: 8 pages, 7 figure

The Impact of a Customs Union between Turkey and the EU on Turkey's Exports to the EU

This paper investigates Turkey's sectoral trade flows to the EU based on panel data from the period 1988 to 2002. Turkey's sixteen most important export sectors are analysed. Emphasis is placed on the role of price competition, EU protection, and transport costs in the export trade between Turkey and the EU. The empirical model used is an extended version of the gravity model. This study is also a contribution to the current discussion of whether Turkey should be granted full EU membership or a privileged partnership with the EU, which for Turkey would mean improved access to the EU market for its products, among other benefits. Our investigation focuses on the latter policy outcome: the impact of deepening the Customs Union between Turkey and the EU and applying the Common Agricultural Policy (CAP) to Turkish agricultural exports. To this end, the impact of the 1996 Customs Union covering most industrial goods and processed agricultural goods, is evaluated on a sectoral level. We also perform simulations to quantify the impact of the potential inclusion of agricultural goods, as well as iron and steel and products thereof, into the full Customs Union between Turkey and the EU which is still to come.Gravity model, Panel data, Sectoral trade flows, Price competition, Transport

Problems in Applying Dynamic Panel Data Models: Theoretical and Empirical Findings

The objective of this paper is twofold: First, the applicability of a widely used dynamic model, the autoregressive distributed lag model (ARDL), is scrutinized in a panel data setting. Second, Chile’s development of market shares in the EU market in the period of 1988 to 2002 is then analyzed in this dynamic framework, testing for the impact of price competitiveness on market shares and searching for estimation methods that allow dealing with the problem of inter-temporal and cross-section correlation of the disturbances. To estimate the coefficients of the ARDL model, FGLS is utilized within the Three Stage Feasible Generalized Least Squares (3SFGLS) and the system Generalized Method of Moments (system GMM) methods. A computation of errors is added to highlight the susceptibility of the model to problems related to underlying model assumptions.Dynamic panel data model, autoregressive distributed lag model; pooled 3Stage Feasible