Physics of Microswimmers - Single Particle Motion and Collective Behavior

Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible due to locomotion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates over inertia. Here, evolution achieved propulsion mechanisms, which overcome and even exploit drag. Prominent propulsion mechanisms are rotating helical flagella, exploited by many bacteria, and snake-like or whip-like motion of eukaryotic flagella, utilized by sperm and algae. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient. The dynamics of microswimmers comprises many facets, which are all required to achieve locomotion. In this article, we review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies. Starting from individual microswimmers, we describe the various propulsion mechanism of biological and synthetic systems and address the hydrodynamic aspects of swimming. This comprises synchronization and the concerted beating of flagella and cilia. In addition, the swimming behavior next to surfaces is examined. Finally, collective and cooperate phenomena of various types of isotropic and anisotropic swimmers with and without hydrodynamic interactions are discussed.Comment: 54 pages, 59 figures, review article, Reports of Progress in Physics (to appear

Conception and Realization of a Chatbot-System to support Psychological and Medical Procedures

As a result of long term researches of Artificial Intelligent, the influence as well as the amount of possible use-cases of chatbots is growing constantly. As to health care, chatbots can be used to simplify the interaction between experts and patients. For example, chatbots can help people who are affected by depression, as the barrier to chat with an application is less high than meeting a real person. While time flexibility can be a benefit for patients, the response to frequently asked questions relieves experts so they can focus on important issues. Consequently, the usage of chatbots in psychological and medical sectors can be a step to improve the health care system. The objective of this master’s thesis is to create a system concept involving a conversational agent, a mobile application and a back-end application to built solutions for the psychological and medical sectors. As all possible use-cases can not be clearly restricted, the concept is designed to be adjustable. Referring to health care, the systems needs to be able to react to critical situations like medical emergencies. However, handling life-threatening cases exceeds the capability of the system and always needs human assistance. Therefore, the concept also includes human participants such as experts. To test the approach, a mobile application was developed that includes a simple conversation using the AI assistant IBM Watson Assistant. In addition, a generic framework was developed to handle multiple third-party chatbots. Furthermore, the mobile application reacts to critical situations, such as the detection of suicidal thoughts or if the user enters an input that is unknown for the system. Moreover, the knowledge base of the chatbot can be extended using a conversation formatted process

Cotunneling renormalization in carbon nanotube quantum dots

We determine the level-shifts induced by cotunneling in a Coulomb blockaded carbon nanotube quantum dot using leading order quasi-degenerate perturbation theory within a single nanotube quartet. It is demonstrated that otherwise degenerate and equally tunnel-coupled $K$ and $K'$ states are mixed by cotunneling and therefore split up in energy except at the particle/hole-symmetric midpoints of the Coulomb diamonds. In the presence of an external magnetic field, we show that cotunneling induces a gate-dependent $g$-factor renormalization, and we outline different scenarios which might be observed experimentally, depending on the values of both intrinsic $KK'$ splitting and spin-orbit coupling.Comment: 12 pages, 7 figure

Explaining Variations in Client Extra Costs between Software Projects Offshored to India

Gaining economic benefits from substantially lower labor costs has been reported as a major reason for offshoring labor-intensive information systems (IS) services to low-wage countries; however, if wage differences are so high, why is there such a high level of variation in the economic success between offshored IS projects? This study argues that offshore outsourcing involves a number of extra costs for the client organization that account for the economic failure of offshore projects. The objective is to disaggregate these extra costs into its constituent parts and to explain why they differ between offshored software projects. The focus is set on software development and maintenance projects that are offshored to Indian vendors. A theoretical framework is developed a priori based on transaction cost economics (TCE) and the knowledge-based view of the firm, complemented by factors that acknowledge the specific offshore context. The framework is empirically explored using a multiple case study design including six offshored software projects in a large German Financial Service institution. The results of our analysis indicate that the client incurs post contractual extra costs for four types of activities: (1) requirements specification and design, (2) knowledge transfer, (3) control, and (4) coordination. In projects that require a high level of client-specific knowledge about idiosyncratic business processes and software systems, these extra costs were found to be substantially higher than in projects were more general knowledge was needed. Notably, these costs most often arose independently from the threat of opportunistic behavior, challenging the predominant TCE logic of market failure. Rather, the client extra costs were particularly high in client-specific projects because the effort for managing the consequences of the knowledge asymmetries between client and vendor were particularly high in these projects. Prior experiences of the vendor with related client projects were found to reduce the level of extra costs but could not fully offset the increase in extra costs in highly client-specific projects. Moreover, cultural and geographic distance between client and vendor as well as personnel turnover were found to increase client extra costs. Slight evidence was found, however, that the cost increasing impact of these factors was also leveraged in projects with a high level of required client-specific knowledge (moderator effect)

The Influence of product-specific determinants on software firms’ international entry mode choices

In an environment of globalization of software and IT services, providing software solutions in international markets has become a strategic necessity for many software firms. When setting up international business operations, software firms need to make a fundamental choice on the distribution arrangements for software and related services in foreign markets. Particularly, such arrangements may either involve contracting with local partners to distribute products and services or extending the firm abroad by establishing wholly-owned subsidiaries or deploying employees. This study focuses on analyzing such boundary choices of software product firms in international markets. Taking a knowledge-based perspective, a research model is developed that outlines the influence of software product and service characteristics on software firms’ international entry mode choices. The research model is tested using PLS based on survey data from internationally operating software firms. The study findings support the knowledge-based reasoning that unique knowledge inherent in a software product that may be required during the sales process can be more easily transferred within firm boundaries. Particularly, the results point out the need for software firms to enter foreign markets through company-owned channels (i.e., wholly-owned subsidiaries or employee deployment) if the business processes and the functionality reflected in software product are highly specific. Likewise, company-owned channels are chosen if a high share of complementary services (e.g., implementation, consulting, training, maintenance, and support) is provided along with the introduction of a software product in a foreign market. In contrast, if significant country-specific adaptations of software products need to be performed, in particular language localization, the required knowledge is most effectively integrated through cooperation with local sales partners

Offshoring of Application Services in the Banking Industry – A Transaction Cost Analysis

Gaining economic benefits from substantially lower labor costs has been reported as a major reason for information systems (IS) offshoring. However, many offshoring projects have failed to achieve expected cost savings, indicating that labor cost savings are offset by additional costs that arise in offshoring projects in certain situations. While previous research on IS offshoring has mostly focused on management issues in offshoring, the focus of this paper is to improve our understanding why the realization of economic benefits varies substantially between offshored software projects. Based on a conceptual framework from transaction cost economics and empirical data from an in-depth case study involving six software development and maintenance projects that were offshored to software vendors in India by a major German financial services organization, two research questions are studied. First, what types of additional costs may arise in offshored software projects? Second, how and why do additional costs vary between projects, considering both task and offshore characteristics? The findings from our analysis indicate that offshoring can lead to increased effort on the client side, both in terms of production costs (requirements specification, knowledge transfer, conceptual development) and transaction costs (vendor coordination, and control). These additional costs are particularly high when the outsourced function is highly asset specific. Moreover, offshore country characteristics such as cultural differences, geographic distance as well as vendor characteristics such as the degree of personnel fluctuation and lack of absorptive capacity can lead to cost add-ons at the client side – in particular when a high degree of human asset specificity is involved in the offshored software projects

Success in offshoring of application development – does culture matter?

Recently, offshoring of information systems (IS) services to external vendors has seen considerable growth. Outsourcing to vendors in foreign countries brings about unique challenges which need to be understood and managed effectively. This paper explores cultural differences in IS offshoring arrangements involving German client organizations that outsource application development activities to Indian vendors. For this purpose, a research framework is developed based on both theoretical considerations and specific empirical observations from multiple case studies. The goal is to (1) explore the nature of cultural differences in offshoring arrangements in depth and to (2) analyze the relationship between those cultural differences and offshoring success. Based on the case findings, implications and practices for the management of offshore development projects are outlined

The Software Prototype as Digital Boundary Object – A Revelatory Longitudinal Innovation Case

With the availability of lower cost but highly skilled software development labor from offshore regions, entrepreneurs from developed countries who do not have software development experience can utilize this workforce to develop innovative software products. In order to succeed in offshored innovation projects, the often extreme knowledge boundaries between the onsite entrepreneur and the offshore software development team have to be overcome. Prior research has proposed that boundary objects are critical for bridging such boundaries – if they are appropriately used. Our longitudinal, revelatory case study of a software innovation project is one of the first to explore the role of the software prototype as a digital boundary object. Our study empirically unpacks five use practices that transform the software prototype into a boundary object such that knowledge boundaries are bridged. Our findings provide new theoretical insights for literature on software innovation and boundary objects, and have implications for practice

Multi-scale geometry interpolation

Interpolating vertex positions among triangle meshes with identical vertex-edge graphs is a fundamental part of many geometric modelling systems. Linear vertex interpolation is robust but fails to preserve local shape. Most recent approaches identify local affine transformations for parts of the mesh, model desired interpolations of the affine transformations, and then optimize vertex positions to conform with the desired transformations. However, the local interpolation of the rotational part is non-trivial for more than two input configurations and ambiguous if the meshes are deformed significantly. We propose a solution to the vertex interpolation problem that starts from interpolating the local metric (edge lengths) and mean curvature (dihedral angles) and makes consistent choices of local affine transformations using shape matching applied to successively larger parts of the mesh. The local interpolation can be applied to any number of input vertex configurations and due to the hierarchical scheme for generating consolidated vertex positions, the approach is fast and can be applied to very large meshes