Remaining Group Members Research Articles

A simple twist of fate. An experiment on election uncertainty and democratic institutions

In this paper we study electoral systems in an experimental governance game in which citizens contribute to a public good and policymakers decide how to distribute it. In the Voting condition, citizens receive information about the policymaker performance (how much she shared of the public good with individual participants), her skills and her altruism, and vote directly for a policymaker for the next election cycle. In the Referendum condition voters receive information about the policymaker's performance before deciding whether to remove her from office in a simpler binary choice (in or out). If they decide to remove the incumbent, a new policymaker is chosen randomly from the remaining group members, in the spirit of referendums like Brexit or the plebiscite about the peace agreements in Colombia. We compare these two electoral mechanisms with two baselines in which the policymaker is never replaced (Baseline) and another one (Random) in which the policymaker is always randomly replaced by another participant. Our results show that both electoral mechanisms are largely effective in improving citizens’ earnings by generating more equitable sharing rules. Citizens in Voting and Referendum extract greater surplus from policymakers than in the other conditions and voting against a candidate (Referendum) is more effective in increasing surplus than voting for a candidate (Voting). Contributions to the public good and conditional cooperation patterns remain strikingly similar in democratic (Referendum and Voting) and non-democratic (Baseline and Random) conditions. Empirical expectations about contributions of other citizens are similar as well. However, we show that policymakers distribute the public good differently in democratic institutions, and more effectively in Referendum than in Voting, as policymakers use clientelist transfers to avoid being replaced. Overall, both democratic institutions are effective in improving citizens’ payoffs by indirectly limiting policymakers’ surplus.

Orthopaedic Research Consortiums: A Review of Scope, Sex and Racial Representation.

Introduction The creation of research groups and consortiums has become more common in all medical and surgical specialities.The purpose of this investigation was to assess and describe collaborative research groups and consortiums within orthopaedic surgery.In addition, we aimed to define the demographics of the research consortium members with particular attention to female and minority members. Methods Journals with a musculoskeletal/orthopaedic focus and a few medical journalswere selected to identify articles published by research groups and consortiums.Articles published from 2020 to 2022 were manually reviewed.Bibliographic information, author informationand level of evidence (LOE) were recorded.For identified consortium members, sex and race were defined in a binary manner. Results A total of 92 research consortiums were identified.A list of members was identified for 77 groups (83.7%), totalling 2,260 researchers. The remaining group members were not able to be identified due to the lack of information in the included publications,research group websites or after communicating with the corresponding author for respective articles.Most researchers were male (n=1,748, 77.3%) and white (n=1,694, 75%). Orthopaedic surgeons comprised 1,613 (71.4%) identified researchers. The most common fellowship training for orthopaedic surgeons was paediatrics (n=370, 16.4%), trauma (n=266, 11.8%)and sports medicine (n=229, 10.1%).The consortiums published 261 articles: women were lead (first) authors in 23% and senior (last) authors in 11.1%. Non-white researchers were lead authors in 24.5% (n=64) and senior authors in 17.2% (n=45). The most common level of evidence was level 3, accounting for 45.6% (n=119) of all publications. Level 1 evidence accounted for 12.6% (n=33) of published articles. Discussion Representation of women in orthopaedic research consortiums exceeds their representation in almost every orthopaedic professional society. There is less publicly available data to compare the involvement of under-represented minorities (URMs) in research consortiums to general practice. Further investigations should analyse possible avenues in which gender and racial disparity could be improved within orthopaedic surgery research.

Identification and Estimation of Installed-Base Effects for Product Adoption Under Sample Attrition and Homophily

This paper studies identification and estimation of installed-base effects for product adoption using group-level panel data in the presence of endogenous sample attrition and homophily. After exploring conditions under which installed-base effects are identified using group-level panel data in the considered setting, I propose a modified BLP approach for estimation. The proposed approach accounts for endogenously changing composition of remaining group members in the simulation of predicted adoption rates, thereby addressing sample attrition. To address homophily, the proposed method performs first-differencing within a given group and uses lags and lagged differences of the installed base as instruments. I present Monte Carlo results to numerically demonstrate the identification issues as well as the performance of the proposed estimation method.

Collaborative Creative Processes That Challenge Us as "Anomaly", and Affirm Our Indigeneity and Enact Our Sovereignty

Collaborative Creative Processes That Challenge Us as "Anomaly", and Affirm Our Indigeneity and Enact Our Sovereignty

Queen succession conflict in the paper wasp Polistes dominula is mitigated by age-based convention

AbstractReproduction in cooperative animal groups is often dominated by one or a few individuals, with the remaining group members relegated to nonreproductive helping roles. This reproductive skew can evolve if helpers receive fitness benefits such as potential future inheritance of the breeding position, but the mechanisms by which inheritance is determined are not well resolved. Polistes paper wasps form highly reproductively skewed groups and inheritance of the breeding position is likely to play a key role in the maintenance of this social structure, making them excellent models for the processes by which simple societies are maintained. Reproductive succession is thought to be determined via an age-based convention in some Polistes species, but there is also evidence for contest-based succession systems in which the replacement queen uses physical aggression to overpower and thereby subordinate her nestmates. Here, we provide evidence that queen succession in colonies of the European paper wasp Polistes dominula is determined via convention rather than contest, with little disruption to the colony’s social functioning. We use queen removal experiments and fine-scale behavioral analyses to confirm that age is a strong predictor of succession, and that behavioral responses to queen removal are restricted to the oldest individuals rather than being experienced equally across the group. We provide the most comprehensive and detailed experimental analysis on the dynamics of breeder succession in a cooperatively breeding invertebrate to date, thereby shedding light on the mechanisms by which animal societies are able to maintain cohesion in the face of within-group conflict.

Multicast Communication using Different Group Key Managements

The most appropriate communication mechanism for transfer of packets from one source to another is multicast IPv6 communication. Nowadays, multicast communication plays a major role in a large number of communication applications. In this multicast communication, the message privacy attains a highest position. The members of multicast are dynamic so they permit the host members to enter and depart the cluster without the permission of remaining group members and, it can't provide any transfer without the interference of host, this may reduce the performance. For security enhancement in multicast communication Group Key Management (GKM) was introduced. There are three different approaches in GKM and they were mainly involved to overcome the issues of host mobility in multicast communication. The challenges that are encountered by these GKM approaches their requirements and challenges was also discussed in this paper. Finally, some questions and their explanations were provided along with it. These GKM approaches will improve the privacy of multicast communication. So, the packets can deliver to the group members without any interference.

Choosing Representatives to Deliver the Message in a Group Violence Intervention

The group-based violence intervention model is predicated on the assumption that individuals who hear credible messages of consequences for further violence will deliver the message to other group members. Using social network analysis, we develop an algorithm of who should receive the message to maximize the spread of the message among the remaining group members. Using a sample of gangs in four different cities we show how the reach of actual call-ins were suboptimal compared to our suggested algorithm. Using simulations, we further show that typically only around a third of the group needs to be delivered the message to achieve complete coverage of the network. We find that even when limiting possible invitees to those under supervision large proportions of groups can be reached if the invitee list is data driven.

Choosing Representatives to Deliver the Message in a Group Violence Intervention

Objectives: The group based violence intervention model is predicated on the assumption that individuals who are delivered the deterrence message spread the message to the remaining group members. We focus on the problem of who should be given the initial message to maximize the reach of the message within the group. Methods: We use social network analysis to create an algorithm to prioritize individuals to deliver the message. Using a sample of twelve gangs in four different cities, we identify the number of members in the dominant set. The edges in the gang networks are defined by being arrested or stopped together in the prior three years. In eight of the gangs we calculate the reach of observed call-ins, and compare these with the sets defined by our algorithm. In four of the gangs we calculate the reach for a strategy that only calls-in members under supervision. Results: The message only needs to be delivered to around 1/3 of the members to reach 100% of the group. Using simulations we show our algorithm identifies the minimal dominant set in the majority of networks. The observed call-ins were often inefficient, and those under supervision could be prioritized more effectively. Conclusions: Group based strategies should monitor their potential reach based on who has been given the message. While only calling-in those under supervision can reach a large proportion of the gang, delivering the message to those not under supervision will likely be needed to reach 100% of the group.

Who are the voluntary leaders? Experimental evidence from a sequential contribution game

We rely on the methodology of Fischbacher et al. (Econ Lett 71(3):397–404, 2001) in order to identify subjects’ behavioral types. We then link the likelihood to act as a leader in a repeated public goods game to the elicited behavioral types. The leader in a group is defined as the subject who voluntarily decides in the first place about his contribution. The leader’s contribution is then reported publicly to the remaining group members who take their contribution decisions simultaneously. Our main findings are that leaders emerge in almost all rounds and that subjects who are identified as conditional cooperators are more likely to act as leaders than other types, e.g., free-riders or triangle-contributors. We also find that voluntary leaders, irrespective of their behavioral type, contribute always more than followers. However, the presence of leadership does not prevent the decay that is commonly observed in linear public goods experiments.

Fatal attack on black-tufted-ear marmosets (Callithrix penicillata) by a Boa constrictor: a simultaneous assault on two juvenile monkeys.

Here we report the first witnessed attack on a marmoset by a constrictor snake. The incident occurred mid-morning in a gallery forest within an altered landscape of the Cerrado region of central Brazil and refers to a fatal attack by a Boa constrictor on two juvenile black-tufted-ear marmosets (Callithrix penicillata) simultaneously. The snake captured both individuals at a height of ~ 4 m while a group of eight marmosets traveled through the subcanopy. The actual strike was not seen. After 2 min, the boa fell to the ground with both marmosets in its coils and proceeded to kill one animal at a time through constriction. Two adult marmosets immediately descended to where the snake held its victims on the ground and attacked it. The snake showed no apparent reaction, and after ~ 1-2 min, the adults rejoined the remaining group members that were mobbing and vocalizing from 5 to 6 m above. The group left the scene ~ 7 min after the onset of the attack and was not seen again. The snake loosened its coils 10 min after its initial strike, left the two carcasses on the ground and stayed behind a nearby tree. Thus, we are not sure if the victims were in fact ingested. This report confirms that marmosets are vulnerable to boid snakes and capable of highly organized and cooperative antipredation behavior. It also suggests that snakes pose a greater threat to callitrichids than previously thought.

A kinematic study and membership analysis of the Lupus star-forming region

This paper is dedicated to investigating the kinematic properties of the Lupus moving group of young stars with the primary objective of deriving individual parallaxes for each group member. We identify those stars in the Lupus star-forming region that define the comoving association of young stars by utilizing our new and improved convergent point search method that allows us to derive the precise position of the convergent point of the comoving association from the stars' proper motions. We used published proper motion catalogs and searched the literature for radial velocities, which are needed to compute individual parallaxes. We supplemented the radial velocity data with new measurements from spectroscopic observations performed with the FEROS spectrograph mounted on the MPG/ESO 2.2m telescope at La Silla. We identify a comoving group with 109 pre-main sequence stars and candidates that define the kinematic properties of the Lupus low-mass star-forming region. We derive individual parallaxes for stars with known radial velocity and tentative parallaxes for the remaining group members by assuming that all stars share the same space motion. The convergent point method, combined with the k-NN algorithm, makes it possible to distinguish the Lupus and Upper Centaurus Lupus stars from the adjacent Scorpius-Centaurus association. We find significant depth effects in this region and show that the classical T Tauri stars, located in the close vicinity of the Lupus molecular clouds, form a background population, while the weak-emission line T Tauri stars are dispersed not only in angular extent but also in depth. The newly derived individual parallaxes will be used in a forthcoming paper to refine the masses and ages of Lupus T Tauri stars, with the aim of better constraining the lifetimes of their circumstellar, protoplanetary disks.

Predation of Alouatta puruensis by Boa constrictor

Reports of successful predator attacks on primates are rare. Primates from all major radiations are particularly susceptible to raptors, carnivores, and snakes. Among New World primates, reports of snake predation are limited to medium- and small-bodied species. Here, we report the first documented case of successful predation of an atelid by a snake-an adult female Purús red howler monkey, Alouatta puruensis, that was subdued by a ca. 2-m-long Boa constrictor in an arboreal setting at a height of 7.5 m above the ground. The victim belonged to a group composed of six individuals (one adult male, two adult females, two juveniles, and one infant) that inhabited a ca. 2.5-ha forest fragment in the State of Rondônia, western Brazilian Amazon. The boa applied the species' typical hunting behavior of striking and immediately coiling around its prey and then killing it through constriction (probably in less than 5 min), but the entire restraint period lasted 38 min. The attack occurred around noon. The howler was swallowed head-first in 76 min. The only group member to respond to the distress vocalization emitted by the victim was the other adult female, which was closest to the location where the attack occurred. This female ran toward the snake, also vocalizing, and hit it with her hands several times, but the snake did not react and she moved off to a nearby tree from where she watched most of the interaction. The remaining group members stayed resting at a height approximately 15 m above the victim in a nearby tree without showing any overt signs of stress, except for a single whimper vocalization. This event indicates that even large-bodied atelids are vulnerable to predation by large snakes and suggests that B. constrictor may be a more common predator of primates.

Behavior and adrenal activity in a group of zoo golden snub-nosed monkeys, Rhinopithecus roxellana, following social structure change

The effects of individual removal by zoo managers on behavior and fecal glucocorticoid changes in snub-nosed monkeys (Rhinopithecus roxellana) were investigated at Beijing Zoo. The results showed that the effect of the removal of three subordinate individuals (DD, male, 4 years; XZZ, male, 3 years and LL, female, 3 years) from a group varied across the remaining group members that may be related to individual’s social status, gender and age. The dominant male was impacted less than subordinate individuals in both the frequency and time duration for the four main behavioral categories. The frequency of stereotypic behavior significantly decreased in the dominant female after the removal of three animals (Z=−2.862, P=0.003). Fluctuations were found in both the behavioral frequency and time duration in other remaining individuals. These findings suggest that small, socially stable groups were somewhat resilient to changes in member composition. Moreover, the cortisol level did not change significantly in the remaining members. An alternative method of hormone assay using fecal samples for vulnerable animals was presented, and that may be useful for monitoring wild golden monkeys and other endangered species of animal.

A New Secure Multicast Key Distribution Scheme Using Tabulation Method

In the present paper, we propose a new scheme for a scalable multicast key distribution scheme. The present scheme is based on the Key Management using Tabulation method of Boolean Function Simplification technique. It explores the use of batching of group membership changes to reduce the frequency, and hence the cost, of key re-distribution operations. It focuses explicitly on the issue of snowballing member removal and presents an algorithm that minimizes the number of messages required to distribute new keys to the remaining group members. The algorithm is used in conjunction with a new scalable multicast key distribution scheme which uses a set of auxiliary keys in order to improve scalability. In contrast to previous schemes which generate a fixed hierarchy of keys, the proposed scheme dynamically generates the most suitable key hierarchy by composing different keys. Our snowballing member removal uses one of the Boolean function simplification techniques called tabulation method, and outperforms all other schemes known to us in terms of message complexity. Most importantly, our technique is superior in minimizing the number of messages when multiple members leave the session in the same round.

Evaluating Steiner-tree heuristics and diameter variations for application layer multicast

Latency reduction in distributed interactive applications has been studied intensively. Such applications may have stringent latency requirements and dynamic user groups. We focus on application-layer multicast with a centralized approach to the group management. The groups are organized in overlay networks that are created using graph algorithms that create a tree structure for the group. A tree has no cycles and uses a small routing table, as opposed to a connected overlay mesh. We investigated a group of spanning tree problems that are referred to as Steiner-tree problems, and we have a particular focus on reducing the diameter of a tree, which is the maximum pairwise latency in a tree. In addition, we focus on reducing the time it takes to execute membership changes. In that context, we use core-selection heuristics to find well-placed client nodes, and edge-pruning algorithms to reduce the number of edges in an otherwise fully meshed overlay. Our edge-pruning algorithms strongly connect well-placed client nodes to the remaining group members, to create new and pruned group graphs. Consequently, when a tree algorithm is applied to a pruned group graph, it is manipulated into creating trees with a smaller diameter. We devised new Steiner-tree heuristics that reduced the diameter, and also proposed new edge-pruning algorithms to make the tree construction faster. These heuristics and algorithms were implemented and analyzed experimentally along with several spanning-tree and core-selection heuristics found in the literature. We found that a full-mesh of shortest paths makes it difficult for Steiner-tree heuristics to find better trees than spanning tree algorithms . The network seen from the application layer is in fact a full mesh of shortest paths. In addition, we found that faster Steiner-tree heuristics that do not explicitly optimize the diameter are able to compete with slower heuristics that do optimize it.

Removing individual rats affects indicators of welfare in the remaining group members

The removal of individuals from social groups, e.g. in order to maintain appropriate stocking densities in groups of rapidly growing young laboratory rats, is often necessary. However, such removals may be stressful and few studies have investigated their effects on the behaviour, physiology and welfare of the remaining group members. In this study we investigated this issue for rats housed at different stocking densities by observing behaviour and recording faecal corticosterone metabolite levels both before and after removal. We found that, irrespective of stocking density, the rats remaining in the home cage significantly increased agonistic behaviour, audible vocalization, aggressive grooming, bar-chewing and climbing behaviour following removal of their cage-mates, and that these behavioural changes were associated with a highly significant post-removal increase in their faecal corticosterone metabolite levels. Taking the behavioural and physiological results together, it appears that the removal of individuals from groups of young laboratory rats resulted in social stress, and thus an apparent impairment of welfare.

Endogenous Group Formation and Public Goods Provision: Exclusion, Exit, Mergers, and Redemption

We test an assortative mechanism whereby groups are formed endogenously, through the use of voting. Once formed, groups play a public-goods game, where the social value of an incremental contribution to the group account increases with the size of the group. Societies of nine people are initially formed randomly into three groups of three people, with identification numbers, and play the game for three periods. Individuals then learn about the average contribution of each individual in one's current own group, as well as the average contribution in other groups, and can decide whether to exit the group. Remaining group members choose whether to exclude any current members from the group; the new groups then choose whether to merge with other existing groups. The exclusion/merge process takes place after every three periods; with 15 periods in one segment and another 15 periods in a second segment (with a re-start) with new identification numbers. We find a great degree of success for this mechanism. The average contribution rate to the group account (excluding the final three periods of a 15-period segment) is 90.2%. We see large and stable groups forming, promoting efficiency: Overall, after the first three periods of a segment, there is at least a 5-person group formed 96% of the time, with at least a 7-person group 66% of the time, and the nine-person grand coalition forming 27% of the time. After the re-start, these figures are even higher: at least a 6-person group formed 100% of the time, at least a 7-person group formed 79% of the time, with the nine-person grand coalition forming 43% of the time. Results from our control sessions indicate that this success is due to the voting mechanism.

Welfare implications of captive primate population management: behavioural and psycho-social effects of female-based contraception, oestrus and male removal in hamadryas baboons ( Papio hamadryas)

In response to over-population, management actions were taken over a 5-year period to reduce group size and slow the population growth rate of hamadryas baboons at Paignton Zoo Environmental Park. Management involved three planned removals of several individuals and implantation of all adult females with Norplant ®, a long-acting contraceptive, expected to be effective for 2–3 years. Possible psycho-social effects of these management strategies were monitored in adult males and females using the rate of occurrence of self-directed behaviour (SDB). SDB was more frequent in males than in females, and in both sexes was significantly more frequent in situations where greater social tension was expected. SDB rates were significantly correlated with overall group size, indicating that the managed reduction in group size was beneficial for the welfare of the remaining group members. Female agonistic interactions were significantly more frequent when they or another female in the harem were in oestrus. However, there was no detectable increase in the rate of SDB of males or females as a result of the contraceptive implants. Despite previous work showing that (a) Norplant ® does not stop normal physical and behavioural signs of oestrus and (b) that female hamadryas baboons in oestrus tend to become more aggressive, our results suggest that implantation with Norplant ® did not cause a substantial increase in social tension in the group as a whole. However, a small effect could have been masked by the simultaneous and greater effects of changing group size.

Insurance-based advantages for subordinate co-foundresses in a temperate paper wasp.

Recent explanations for the evolution of eusociality, focusing more on costs and benefits than relatedness, are largely untested. We validate one such model by showing that helpers in foundress groups of the paper wasp Polistes dominulus benefit from an insurance-based mechanism known as Assured Fitness Returns (AFRs). Experimental helper removals left remaining group members with more offspring than they would normally rear. Reduced groups succeeded in preserving the dead helpers' investment by rearing these extra offspring, even when helper removals occurred long before worker emergence. While helpers clearly gained from AFRs, offspring of lone foundresses failed after foundress death, so that AFRs represent a true advantage for helpers. Smaller, less valuable offspring were probably sacrificed to feed larger offspring, but reduced groups did not preferentially attract joiners or increase their foraging effort to compensate for their smaller workforce. We failed to detect a second insurance-based advantage, Survivorship Insurance, in which larger groups are less likely to fail than smaller groups. We suggest that through their use of small offspring as a food store to cope with temporary shortages, wasps may be less susceptible than vertebrates to offspring failure following the death of group members.

The Effect of Structural Preferences, Temperature, and Social Factors on Visibility in Western Lowland Gorillas

Postoccupancy evaluations are common in determining successful design elements in the human setting, but they are rarely employed in zoological parks. The current study evaluated how structural preferences, temperature, and social factors affected the visibility of four groups of gorillas to the public. Although the majority of structures were located in visible portions of the exhibit, structures had a negative effect on visibility because of the gorillas’ strong preference for a single typeof structure(buildings) located primarily in nonvisibleparts of theexhibits. Tem perature and visibility were linearly related, with increasing temperatures corresponding with decreasing visibility. The removal of an animal from the group significantly affected the visibility of the remaining group members. The authors’ results reinforce the need for exhibit designers to consider the relationships between animal behavior and environmental variables and to work with captive managers to create exhibits that meet the needs of individual animals.