SO(3) nonlinear σ model for a spiral phase in the spin-fermion model

Starting from a doped spin-fermion model for the CuO₂ planes in high-T_c superconductors, we derive an effective continuum theory for the spin degrees of freedom by means of a gradient expansion. We assume an incommmensurate, spiral configuration for the spins. Extending our previous treatment of a planar spiral, we allow for three-dimensional fluctuations of the spin fields, which are described by an S0(3) matrix order parameter. The continuum limit is obtained by a systematic expansion in powers of a short distance cutoff. The occurring infinite series is summed to all orders using a combinatorial method which exploits the constraint obeyed by the S0(3) order parameter. The resulting continuum theory is given by an S0(3) quantum nonlinear model, where the influence of doping is contained in the fermionic susceptibilities that enter into the coupling constants of the model.     

Tuning the Intermolecular Electrostatic Interaction toward High-Efficiency and Low-Cost Organic Solar Cells

Organic solar cells (OSCs) have achieved much progress with rapidly increasing power conversion efficiencies (PCEs). It should be noted that the top-performance OSCs are generally consisted of active materials with complex chemical structures, resulting in high costs. Here, combining the material design and morphology control, high-efficiency OSCs are fabricated by a low-cost donor: acceptor blend. A completely non-fused electron acceptor named Tz is designed and synthesized via introducing thiazole units on both sides of a bithiophene core, which shows an outstanding PCE of 13.3% with a typical polythiophene donor. More importantly, optimization guidelines are presented to get excellent morphology for low-cost donor:acceptor systems. Three polythiophenes are selected, poly(3-hexylthiophene) and its two derivatives with electron-withdrawing substitutions (PDCBT and PDCBT-2F), as donors to fabricate the cell devices. The computational and experimental data reveal that decreasing the electrostatic interaction between polythiophene and Tz is the key to getting a suppressed miscibility and thus a high phase purity. This study provides insight into the molecular design and donor:acceptor matching requirements for high-efficiency and low-cost OSCs.     

Magnetic Properties of Thermal Sprayed Tungsten Carbide–Cobalt Coatings

In the information age, the storage and accessibility of data is of vital importance. There are several possibilities to fulfill this task. Magnetic storage of data is a well‐established method and the range of materials used is continuously extended. In this study, the magnetic remanence of thermally sprayed tungsten carbide–cobalt (WCCo)‐coatings in dependence of their thickness is examined. Two magnetic fields differing in value and geometry are imprinted into the coatings and the resulting remanence field is measured. It is found that there are two effects, which in combination determine the effective value of the magnetic remanence usable for magnetic data storage.

     

Service integrators in business networks—the importance of relationship values

To realise the potentials of CRM (customer relationship management), relationship-specific processes need to be designed and implemented in companies. This is all the more important and complicated in business networks where two or more actors collaborate to serve the customers. A good collaboration within business networks is the basis for understanding the customer process and identifying customer needs. But, even in these days of customer orientation, transaction orientation is still a matter of strong interest, and the following questions remain to be answered: What is the difference between relationship-oriented processes and transaction-oriented processes, and how can relationship-oriented processes be designed for a business network? The authors give first answers to both questions by using a systematic, goal-oriented specialisation of generic actions. To give an example, one relationship-oriented process will be designed and specified for a certain customer process in the course of this paper.     

Reading from computer screen versus reading from paper: does it still make a difference?

Four experiments were conducted to test whether recent developments in display technology would suffice to eliminate the well-known disadvantages in reading from screen as compared with paper. Proofreading speed and performance were equal for a TFT-LCD and a paper display, but there were more symptoms of eyestrain in the screen condition accompanied by a strong preference for paper (Experiment 1). These results were replicated using a longer reading duration (Experiment 2). Additional experiments were conducted to test hypotheses about the reasons for the higher amount of eyestrain associated with reading from screen. Reduced screen luminance did not change the pattern of results (Experiment 3), but positioning both displays in equal inclination angles eliminated the differences in eyestrain symptoms and increased proofreading speed in the screen condition (Experiment 4). A paper-like positioning of TFT-LCDs seems to enable unimpaired reading without evidence of increased physical strain.

Practitioner Summary: Given the developments in screen technology, a re-assessment of the differences in proofreading speed and performance, well-being, and preference between computer screen and paper was conducted. State-of-the-art TFT-LCDs enable unimpaired reading, but a book-like positioning of screens seems necessary to minimise eyestrain symptoms.     

User-centred process for the definition of free-hand gestures applied to controlling music playback

Music is a fundamental part of most cultures. Controlling music playback has commonly been used to demonstrate new interaction techniques and algorithms. In particular, controlling music playback has been used to demonstrate and evaluate gesture recognition algorithms. Previous work, however, used gestures that have been defined based on intuition, the developers’ preferences, and the respective algorithm’s capabilities. In this paper we propose a refined process for deriving gestures from constant user feedback. Using this process every result and design decision is validated in the subsequent step of the process. Therefore, comprehensive feedback can be collected from each of the conducted user studies. Along the process we develop a set of free-hand gestures for controlling music playback. The situational context is analysed to shape the usage scenario and derive an initial set of necessary functions. In a successive user study the set of functions is validated and proposals for gestures are collected from participants for each function. Two gesture sets containing static and dynamic gestures are derived and analysed in a comparative evaluation. The comparative evaluation shows the suitability of the identified gestures and allows further refinement. Our results indicate that the proposed process, that includes validation of each design decision, improves the final results. By using the process to identify gestures for controlling music playback we not only show that the refined process can successfully be applied, but we also provide a consistent gesture set that can serve as a realistic benchmark for gesture recognition algorithms.     

Stochastic Models for Pad Structure and Pad Conditioning Used in Chemical-Mechanical Polishing

Stochastic models are presented for the structure and conditioning of pads used in chemical-mechanical polishing of wafers. First the one-dimensional distribution function of surface depth in the case of a conditioned solid pad is described. Then, for characterizing the structure of a foamed pad, the theory of random closed sets is applied. An important distributional characteristic of a random closed set, the linear contact distribution function, yields the contribution to surface depth resulting from pores. As a special example the Boolean model is considered. This leads to a formula that describes the variability of the surface of a conditioned foamed pad after a certain time. Simulations and experimental data show a good agreement between theory and reality.     

Fluid-Induced Seismicity: Theory, Modeling, and Applications

Operations including borehole fluid injections are typical for exploration and development of hydrocarbon or geothermic reservoirs. Microseismicity occurring during such operations has a large potential for understanding physics of the seismogenic process as well as in obtaining detailed information about reservoirs at locations as far as several kilometers from boreholes. We propose that the phenomenon of microseismicity triggering by borehole fluid injections is related to the process of the Frenkel–Biot slow wave propagation. In the low-frequency range (hours or days of fluid injection durations) this process reduces to the pore-pressure diffusion. We search for diffusion-related features of induced microseismicity. Two types of such signatures are considered. The first one is related to the geometry of microseismic clouds. Another type of signature is related to the probability of microearthquakes. On this basis we introduce a concept for interpretation of microseismic data which provides a possibility to infer information about hydraulic properties of rocks. Such information can be of significant importance for industrial applications and for understanding physical properties of geological structures.     

Salmonella in eggs: From shopping to consumption—A review providing an evidence-based analysis of risk factors

Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestinal infections worldwide. A high number of cases and outbreaks of salmonellosis are associated with the consumption of eggs and egg products, and several of these occur at the household level. The aim of the current study is to critically evaluate the current status of knowledge on Salmonella in eggs from a consumer's perspective, analyzing the hazard occurrence and the good practices that should be applied to reduce salmonellosis risk. Following a HACCP (Hazard Analysis and Critical Control Point) based approach, some steps along the food journey were identified as Critical Consumer Handling (CCH)—steps in which consumers, through their behavior or choice, can significantly reduce the level of Salmonella in eggs and egg products. From shopping/collecting to consumption, each of these steps is discussed in this review to provide an evidence-based overview of risk factors of human salmonellosis related to egg consumption. The main message to consumers is to choose Salmonella-free eggs (those that some official entity or producer guarantees that does not contain Salmonella), when available, especially for dishes that are not fully heat treated. Second, as guaranteed Salmonella-free eggs are only available in a few countries, refrigerated storage from the point of collection and proper cooking will significantly reduce the risk of salmonellosis. This will require a revision of the actual recommendations/regulations, as not all ensure that eggs are maintained at temperatures that prevent growth of Salmonella from collection until the time of purchasing.