Modern temporal network theory: A colloquium

The power of any kind of network approach lies in the ability to simplify a complex system so that one can better understand its function as a whole. Sometimes it is beneficial, however, to include more information than in a simple graph of only nodes and links. Adding information about times of interactions can make predictions and mechanistic understanding more accurate. The drawback, however, is that there are not so many methods available, partly because temporal networks is a relatively young field, partly because it more difficult to develop such methods compared to for static networks. In this colloquium, we review the methods to analyze and model temporal networks and processes taking place on them, focusing mainly on the last three years. This includes the spreading of infectious disease, opinions, rumors, in social networks; information packets in computer networks; various types of signaling in biology, and more. We also discuss future directions.Comment: Final accepted versio

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Effect of manipulating feathers of laying hens on the incidence of feather pecking and cannibalism

Feather pecking is a problem in commercial laying hens, particularly in loose-housing systems, where many hens can be affected by only a few feather peckers. In addition, feather pecking can become an even larger problem if it spreads throughout the flock. There are several possible ways that feather pecking may spread. The simplest way is that one hen may damage the feathers of a hen, and another hen may find the damaged feathers an attractive pecking target. The aim of this experiment was to determine if damaged feathers were feather-pecked more than undamaged feathers on the same body area, and to determine whether some types of feather-body area manipulations were preferred over others as pecking stimuli. Manipulations involved damaging the feathers on the rump, tail or belly of different hens, with two or three levels of severity of manipulation at each body area. Sixteen groups of 11 Lohmann Brown hens between 26 and 28 weeks were observed with the recipient, the feather pecker and the body area that was pecked all being recorded. The feather pecks were classified separately as either gentle or severe. Damaged feathers received significantly more severe feather pecks than undamaged feathers. There were also more gentle feather pecks to damaged feathers, although this did not reach statistical significance. The feather-body area manipulations that received the greatest number of severe feather pecks were the tail feathers when they were cut very short, the rump feathers when they were trimmed, and the rump when feathers were removed. These results support the suggestion that feather pecking does indeed spread through flocks by damaged feathers becoming an attractive target for feather-pecking behaviour. An unexpected result of performing the feather manipulations was an outbreak of cannibalism in half of the experimental groups. Even though there was no visible damage to the skin of the hens after having the feathers manipulated, 13 of the 16 attacked hens were wounded on the part of the body where the feathers had been damaged in some way

The social transmission of feather pecking in laying hens: effects of environment and age

Abnormal behaviours, such as feather pecking, can become an even greater problem if they spread through the flock. Domestic hens are a social species and it has been suggested that feather pecking behaviour can be socially transmitted from few feather pecking individuals to many. The purpose of this experiment was to investigate whether feather pecking is transmitted from an experimental strain of high feather peckers to an experimental strain of low feather peckers when housed together. The effects of environment and age were also investigated. Four hundred and twenty chicks were housed in either cages or pens in one of three treatment groups; all high feather peckers, all low feather peckers, and a mixed group of half high feather peckers and half low feather peckers. During the rearing phase, severe and gentle feather pecks were recorded at 13–15 weeks and feather plumage scored at 12 and 17 weeks. At 17 weeks of age, the groups of mixed hens were removed from the study and the remaining hens resorted into the same three treatment groups. During the laying phase, severe and gentle feather pecks were recorded at 30–32 weeks of age and feather plumage was scored at 29 weeks of age. There was significantly less feather pecking and plumage damage in the pens than in the cages. There was no evidence of severe feather pecking spreading from feather peckers to non-feather peckers, even when actual rates of feather pecking were examined rather than only considering the strain of hen. There was some evidence that gentle feather pecking was transmitted in laying hens housed in cages. However, as gentle feather pecking does not lead to plumage damage, this is less relevant to commercial practice

A Scenario Analysis on the Implementation of a Farm Animal Welfare Assessment System

There have been important developments in the measurement of farm animal welfare in recent years. Measuring animal welfare is one thing, implementing a farm animal welfare assessment system another. The implementation of such a system occurs in an environment that is influenced by economic, political, technological and socio-cultural factors which interact with each other. This creates enormous complexity, generates a huge number of different potential ‘futures’, and makes the eventual impact that the system will have on the welfare of farm animals uncertain. This article draws upon strategic management literature to apply scenario analysis as a technique to help understand the variance of the uncertainty associated with the implementation of an animal welfare assessment scheme. Specifically, it develops two extreme scenarios based on a theoretical European-wide implementation: one scenario in which all uncertain factors influence the implementation of the assessment system in a negative way, and one scenario in which all these factors have positive impacts. These scenarios provide insight into the variance of possible futures in which the system may have to function. Although consumers are an important stakeholder group, their role in creating uncertainty for the system may be overestimated; it is apparent that the roles of companies, brands and certification organisations deserve significant attention, as well as any relevant institutional structure. Keywords: animal welfare, certification, farm animal welfare assessment, implementation, policy, scenario analysi

The effect of an audience on the gakel-call and other frustration behaviours in the laying hen (Gallus gallus domesticus)

When thwarted in a behaviour, laying hens show an increase in stereotyped pacing, displacement preening and a specific vocalisation known as the 'gakel-call'. How these behaviours, which might serve as indicators of welfare, are influenced by social factors is not yet known. In this study, we investigated the effect of an audience (another bird or a human) on the expression of the gakel-call and other behaviours indicating frustration. Twenty-four Lohman Brown hens were trained to gain free access to food in a test cage. Sixteen hens were used as test birds and eight as non-test audience birds. The food-deprived test hens were tested for 15 min in a non-thwarting situation (food freely available) and for 15 min in a thwarting situation (food covered but visible). For both situations we investigated four different treatments: no audience in the adjacent cage; a non-thwarted audience bird in the adjacent cage; a thwarted audience bird in the adjacent cage; and finally a human audience. The durations of stereotyped pacing and displacement preening were significantly higher in test birds during thwarting than during non-thwarting; thwarted birds also gave significantly more gakel-calls compared to non-thwarted birds. The test birds, and also the audience birds, gave more gakel-calls when thwarted in the presence of a thwarted conspecific than when in the presence of a non-thwarted bird, but there were no significant differences in stereotyped pacing or displacement preening, which are usually associated with frustration. In conclusion, this study supports the view that the gakel-call signals frustration in laying hens. Furthermore, the state of the audience influences the occurrence of gakel-calls in thwarted hens. Thus, when using the gakel-call as a welfare-indicator, the social aspects of the vocal expression of frustration in laying hens should not be overlooke