Phase transitions in systems with two species of molecular motors

Systems with two species of active molecular motors moving on (cytoskeletal) filaments into opposite directions are studied theoretically using driven lattice gas models. The motors can unbind from and rebind to the filaments. Two motors are more likely to bind on adjacent filament sites if they belong to the same species. These systems exhibit (i) Continuous phase transitions towards states with spontaneously broken symmetry, where one motor species is largely excluded from the filament, (ii) Hysteresis of the total current upon varying the relative concentrations of the two motor species, and (iii) Coexistence of traffic lanes with opposite directionality in multi-filament systems. These theoretical predictions should be experimentally accessible.Comment: 7 pages, 4 figures, epl style (.cls-file included), to appear in Europhys. Lett. (http://www.edpsciences.org/epl

Movements of molecular motors: Ratchets, random walks and traffic phenomena

Processive molecular motors which drive the traffic of organelles in cells move in a directed way along cytoskeletal filaments. On large time scales, they perform motor walks, i.e., peculiar random walks which arise from the repeated unbinding from and rebinding to filaments. Unbound motors perform Brownian motion in the surrounding fluid. In addition, the traffic of molecular motors exhibits many cooperative phenomena. In particular, it faces similar problems as the traffic on streets such as the occurrence of traffic jams and the coordination of (two-way) traffic. These issues are studied here theoretically using lattice models.Comment: latex, uses elsart.cls and phyeauth.cls (included), 10 pages, 6 figures, to appear in the proceedings of FQMT'04, Pragu

Determining Returns to Storage: USDA Data versus Micro Level Data

USDA data are commonly used to determine producers' returns to storage. Aggregating data may result in a loss of information, leading to underestimated returns. This study compares USDA and elevator data from Oklahoma to determine how much USDA data underestimates returns. Results indicate USDA data only slightly underestimate returns to storage.Research Methods/ Statistical Methods,

The Preference for Round Number Prices

This study determines if a preference for round prices exists in the wheat market and how wheat sales react to price movements around whole dollar amounts. The results show round prices are slightly more prevalent than non-round prices and that transactions increase when price moves above a whole dollar amount.Demand and Price Analysis,

Digital Supply Chains and the Human Factor—A Structured Synopsis

Digital developments and changes in the production, supply chain and logistics sector as well as specific concepts like automation and Industry 4.0 or the Internet of Things are omnipresent. Especially the human role in such settings experiences important changes, which has not been adequately addressed in research yet. This introduction chapter contains an overview of elements encountered in digitalization processes in order to ensure sustainable work environments and efficient Human-Computer Interaction settings for the benefit of workers and organizations. Thus, it is the aim of this chapter to provide a structured synopsis to consider the human factor in analyzing digital work processes. This synopsis is aligned with typical workflow developments in digitalization projects and can be transferred to different work settings in supply chains. Finally, we outline the chapter structure of this book within four thematic sections in order to provide a joint storyline on investigating the human factor in digital supply chains

Transport by molecular motors in the presence of static defects

The transport by molecular motors along cytoskeletal filaments is studied theoretically in the presence of static defects. The movements of single motors are described as biased random walks along the filament as well as binding to and unbinding from the filament. Three basic types of defects are distinguished, which differ from normal filament sites only in one of the motors' transition probabilities. Both stepping defects with a reduced probability for forward steps and unbinding defects with an increased probability for motor unbinding strongly reduce the velocities and the run lengths of the motors with increasing defect density. For transport by single motors, binding defects with a reduced probability for motor binding have a relatively small effect on the transport properties. For cargo transport by motors teams, binding defects also change the effective unbinding rate of the cargo particles and are expected to have a stronger effect.Comment: 20 pages, latex, 7 figures, 1 tabl

Workforce between autonomy and control – effects of digitalization on employment relationships in the logistics industry

Logistics as a global innovative industry is experiencing fundamental changes because of digitalization. New business models are emerging and the organization of work is changing. In this way, work processes can be recorded and controlled digitally and transparently. This article examines the effects of these technological changes on logistics workers and their employment relationships. The aim is to analyze the digitalization of urban food logistics regarding the perception of autonomy and control from the worker’s perspective and the resulting effects on the design of employment relationships. The analysis is based on a qualitative study with professional truck drivers and cyclists in urban food logistics. The results show a ambivalence between the concurrence of autonomy and control in daily work, which can be connected to the integration of new technologies into work organization as well as the role of managers. Finally, requirements for a structured consideration of this interrelationship in digitalization processes are presented

Efficiency Measurement in Digitalized Work Systems of Transport Logistics

Digitalization is a major trend and challenge in most industries and sectors of societies. Still, quantitative insights regarding the impacts of digitalization are missing. This chapter is reporting a first approach using Data Envelopment Analysis (DEA) for measuring efficiency results of digitalization steps in a retail logistics context. Aspiring to quantify the performance of professional truck drivers during a digital turnover related to mobile devices, we evaluate truck loading processes. As inputs we use loading time and costs. Outputs are load factor of units, invoice charged to shops, and the value of the damages during truck loading. The findings indicate that a change in the level of digitalization entails a loss of the efficiency level in the first instance, which can be compensated and even surpassed later. When applying linear regression analysis, we prove a low statistical linear relationship of age and efficiency plus a strong statistical linear relationship of employer size and efficiency as well as period of employment and efficiency, always regarding the changing levels of digitalization in the working system of professional truck drivers. For practitioners in retail logistics, we derive the importance of employee retention programs for human resource management, along with a positive working environment provided for truck drivers to reduce fluctuation effects. Furthermore, we advise designing software for truck drivers as commonplace as possible and in the style of widespread smartphone software user interfaces

Smart and efficient: Learning curves in manual and human-robot order picking systems

Order picking has been identified as the most labour-intensive, as well as costly activity within warehouse logistics and is experiencing significant changes due to new technologies in the forms of artificial intelligence (AI) and automation. One fundamental question concerns the employees learning progress in human-robot picking systems compared to existing manual technologies. Therefore, this paper presents an empirical analysis of learning curves in manual pick-by-voice (n=30 pickers) and semiautomated (n=20 pickers) order picking. Aspiring to measure the individual learning progress without a priori assumptions, this publication is the first to apply Data Envelopment Analysis and examine order pickers learning curves in real application scenarios. The findings indicate that automating human work accelerates the individual learning progress in human-robot picking systems

Traffic of Molecular Motors

Molecular motors perform active movements along cytoskeletal filaments and drive the traffic of organelles and other cargo particles in cells. In contrast to the macroscopic traffic of cars, however, the traffic of molecular motors is characterized by a finite walking distance (or run length) after which a motor unbinds from the filament along which it moves. Unbound motors perform Brownian motion in the surrounding aqueous solution until they rebind to a filament. We use variants of driven lattice gas models to describe the interplay of their active movements, the unbound diffusion, and the binding/unbinding dynamics. If the motor concentration is large, motor-motor interactions become important and lead to a variety of cooperative traffic phenomena such as traffic jams on the filaments, boundary-induced phase transitions, and spontaneous symmetry breaking in systems with two species of motors. If the filament is surrounded by a large reservoir of motors, the jam length, i.e., the extension of the traffic jams is of the order of the walking distance. Much longer jams can be found in confined geometries such as tube-like compartments.Comment: 10 pages, latex, uses Springer styles (included), to appear in the Proceedings of "Traffic and Granular Flow 2005