Costs and benefits of social relationships in the collective motion of bird flocks

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record.Supplementary Figs. 1–12 and Supplementary Tables 1–3 are available in the Supplementary Information. Raw images captured by one of the four cameras and the reconstructed birds’ 3D movement trajectories are provided in Supplementary Videos 1–6. Plain text files, each including bird ID number, position, time, velocity, acceleration and wingbeat frequency at every time step, are provided in Supplementary Data 1–7. A plain text file that includes mean wingbeat frequency, flight speed and local density (approximated by the number of neighbours within a distance of 5 m from the focal bird) for paired and unpaired birds in six flocks, as well as for birds flying alone, is provided in Supplementary Data 8. All data required to reproduce the results in this study are included in Supplementary Data 1–8. Supplementary Data and Supplementary Videos are available at https://figshare.com/s/c55eb82bab800571d25d.Current understanding of collective behaviour in nature is based largely on models that assume that identical agents obey the same interaction rules, but in reality interactions may be influenced by social relationships among group members. Here, we show that social relationships transform local interactions and collective dynamics. We tracked individuals’ three-dimensional trajectories within flocks of jackdaws, a species that forms lifelong pair-bonds. Reflecting this social system, we find that flocks contain internal sub-structure, with discrete pairs of individuals tied together by spring-like effective forces. Within flocks, paired birds interacted with fewer neighbours than unpaired birds and flapped their wings more slowly, which may result in energy savings. However, flocks with more paired birds had shorter correlation lengths, which is likely to inhibit efficient information transfer through the flock. Similar changes to group properties emerge naturally from a generic self-propelled particle model. These results reveal a critical tension between individual- and group-level benefits during collective behaviour in species with differentiated social relationships, and have major evolutionary and cognitive implications.Human Frontiers in Science Programm

Local interactions and their group-level consequences in flocking jackdaws

This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this recordData accessibility: Data and code are available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.kb8js06As one of nature's most striking examples of collective behaviour, bird flocks have attracted extensive research. However, we still lack an understanding of the attractive and repulsive forces that govern interactions between individuals within flocks and how these forces influence neighbours' relative positions and ultimately determine the shape of flocks. We address these issues by analysing the three-dimensional movements of wild jackdaws (Corvus monedula) in flocks containing 2–338 individuals. We quantify the social interaction forces in large, airborne flocks and find that these forces are highly anisotropic. The long-range attraction in the direction perpendicular to the movement direction is stronger than that along it, and the short-range repulsion is generated mainly by turning rather than changing speed. We explain this phenomenon by considering wingbeat frequency and the change in kinetic and gravitational potential energy during flight, and find that changing the direction of movement is less energetically costly than adjusting speed for birds. Furthermore, our data show that collision avoidance by turning can alter local neighbour distributions and ultimately change the group shape. Our results illustrate the macroscopic consequences of anisotropic interaction forces in bird flocks, and help to draw links between group structure, local interactions and the biophysics of animal locomotion.Human Frontiers in Science Programm

A hybrid knowledge-based system for strategic purchasing

The aim of this paper is to show how knowledge-based systems technology can assist in the area of strategic purchasing. The authors discuss a knowledge-based system (KBS) designed to help companies in the make or buy decision, which is arguably the most fundamental component of manufacturing strategy. As part of the development process, procurement managers in ten multi-national companies were interviewed to determine current make or buy practice and elicit opinions on how the decision-making process could be enhanced. The general consensus was that a formal structure was needed along with computerized support at various stages in the process. The model was developed conceptually from the analysis of these interviews with procurement managers and also through a thorough literature survey of the area. The next stage was to computerize the most important components of the system to enable feedback from procurement managers in two of the multi-nationals first interviewed. Within the description of this KBS there is specific focus on the issues involved in the application of case-based reasoning (CBR) techniques and Multi-Attribute Analysis (MAA) to the automation of the make or buy decision. The development of this system is intended to illustrate that a case-based system should be capable of providing sound solutions utilizing relatively small case libraries, while avoiding a large rule base and long rule chains necessary if rule-based reasoning was used exclusively

A decision support framework for strategic purchasing

This paper illustrates that the make or buy is a strategic decision and has implications for the overall corporate strategy of the organisation by describing a model which involves analysing a number of strategic factors. In recent years, many companies have been moving significantly away from “making” towards “buying”. However, research has revealed that make or buy decisions are rarely taken within a thoroughly strategic perspective. It has been shown that many firms adopt a short-term perspective and are motivated primarily by the search for short-term cost reductions. It is argued that make or buy decisions are made most frequently by default with little consideration for the long-run competitiveness of the organisation. An outline of three key problems encountered by companies in their efforts to formulate an effective make or buy decision is presented, in order to illustrate the weaknesses in current make or buy practice. The make or buy model described in this paper attempts to overcome these problems by offering an organisation a conceptual framework to follow in the sourcing decision

A picornaviral ‘2A-like’ sequence based tricistronic vector allowing for high level therapeutic gene expression coupled to a dual reporter system.

The 2A-like sequences from members of the picornavirus family were utilized to construct a tricistronic vector bearing the human iduronidase (IDUA) gene along with the firefly luciferase and DsRed2 reporter genes. The 2A-like sequences mediate a cotranslational cleavage event resulting in the release of each individual protein product. Efficient cleavage was observed and all three proteins were functional in vitro and in vivo, allowing for supratherapeutic IDUA enzyme levels and the coexpression of luciferase and DsRed2 expression, which enabled us to track gene expression.</p

A picornaviral ‘2A-like’ sequence based tricistronic vector allowing for high level therapeutic gene expression coupled to a dual reporter system.

The 2A-like sequences from members of the picornavirus family were utilized to construct a tricistronic vector bearing the human iduronidase (IDUA) gene along with the firefly luciferase and DsRed2 reporter genes. The 2A-like sequences mediate a cotranslational cleavage event resulting in the release of each individual protein product. Efficient cleavage was observed and all three proteins were functional in vitro and in vivo, allowing for supratherapeutic IDUA enzyme levels and the coexpression of luciferase and DsRed2 expression, which enabled us to track gene expression.</p