Global sourcing – a critical reconsideration of sector definitions

I introduce an alternative parameter-based definition of component- and headquarter-intensive sectors into the seminal model of global sourcing by Antràs and Helpman (2004, JPE). This approach overcomes problems of the original sector definition like counter intuitive classifications or industries that are not classified as either component- or headquarter-intensive. The strong empirical evidence for the model`s predictions is also based on a similar sector definition. With a numerical approach I show that a richer set of sourcing modes can arise in equilibrium. Nonetheless, the main results of Antràs and Helpman are robust.Multinational firms, outsourcing, intra-firm trade, offshoring, vertical FDI

Global Sourcing of Complex Production Processes

We develop a theory of a firm in an incomplete contracts environment which decides on its complexity, organization, and global scale. Specifically, the firm decides i) how thinly it wants to slice its production process by choosing the mass of symmetric intermediate inputs that are simultaneously combined to a final product, ii) if the supplier of each component is an external contractor or an integrated affiliate, and iii) if that component is offshored to a foreign country. We also consider the case of asymmetric inputs. Our model leads to a rich set of novel predictions about the structure of multinational firms that are consistent with stylized facts from the recent empirical literature.multinational firms, outsourcing, intra-firm trade, offshoring, vertical FDI

Global Sourcing of Complex Production Processes

We develop a theory of a firm in an environment with incomplete contracts. The firm’s headquarter decides on the complexity, the organization, and the global scale of its production process. Specifically, it decides: i) on the mass of symmetric intermediate inputs that are part of the value chain, ii) if the supplier of each component is an external contractor or an integrated affiliate, and iii) if the supplier is offshored to a foreign low-wage country. Afterwards we consider a related scenario where the headquarter contracts with a given number of two asymmetric suppliers. Our model is consistent with several stylized facts from the recent literature that existing theories of multinational firms cannot account for.multinational firms, outsourcing, intra-firm trade, offshoring, vertical FDI

Differential K-theory. A survey

Generalized differential cohomology theories, in particular differential K-theory (often called "smooth K-theory"), are becoming an important tool in differential geometry and in mathematical physics. In this survey, we describe the developments of the recent decades in this area. In particular, we discuss axiomatic characterizations of differential K-theory (and that these uniquely characterize differential K-theory). We describe several explicit constructions, based on vector bundles, on families of differential operators, or using homotopy theory and classifying spaces. We explain the most important properties, in particular about the multiplicative structure and push-forward maps and will state versions of the Riemann-Roch theorem and of Atiyah-Singer family index theorem for differential K-theory.Comment: 50 pages, report based in particular on work done sponsored the DFG SSP "Globale Differentialgeometrie". v2: final version (only typos corrected), to appear in C. B\"ar et al. (eds.), Global Differential Geometry, Springer Proceedings in Mathematics 17, Springer-Verlag Berlin Heidelberg 201

Role of anisotropy for protein-protein encounter

Protein-protein interactions comprise both transport and reaction steps. During the transport step, anisotropy of proteins and their complexes is important both for hydrodynamic diffusion and accessibility of the binding site. Using a Brownian dynamics approach and extensive computer simulations, we quantify the effect of anisotropy on the encounter rate of ellipsoidal particles covered with spherical encounter patches. We show that the encounter rate $k$ depends on the aspect ratios $\xi$ mainly through steric effects, while anisotropic diffusion has only a little effect. Calculating analytically the crossover times from anisotropic to isotropic diffusion in three dimensions, we find that they are much smaller than typical protein encounter times, in agreement with our numerical results.Comment: 4 pages, Revtex with 3 figures, to appear as a Rapid Communication in Physical Review

Spatial Diffuseness Features for DNN-Based Speech Recognition in Noisy and Reverberant Environments

We propose a spatial diffuseness feature for deep neural network (DNN)-based automatic speech recognition to improve recognition accuracy in reverberant and noisy environments. The feature is computed in real-time from multiple microphone signals without requiring knowledge or estimation of the direction of arrival, and represents the relative amount of diffuse noise in each time and frequency bin. It is shown that using the diffuseness feature as an additional input to a DNN-based acoustic model leads to a reduced word error rate for the REVERB challenge corpus, both compared to logmelspec features extracted from noisy signals, and features enhanced by spectral subtraction.Comment: accepted for ICASSP201