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The article presents the results of the numerical simulation of the signal formation process of the background wires of self-powered neutron detectors (SPND) under the action of gamma radiation in the VVER-1000 core using MCNP code. The validation of the MCNP model was carried out on the results of experimental determination of the current of the background wires of the SPND, obtained at three different power units with VVER-1000 during the fuel campaign. The article also proposes a new gamma-ray method for determining the thermal power of the VVER-1000 reactor (TPR) based on the signals from the background wires of the SPND. TPR is an important safety parameter of VVER-1000, therefore, increasing the accuracy of determining TPR with the introduction of an additional gamma method for its determination is an urgent task, given the plans to increase the TPR of VVER-1000. The results of the experimental determination of the VVER-1000 TPR by the traditional neutron method based on the SPND signals are presented, and problematic issues regarding the error in determining the TPR by the neutron method are pointed out. The article presents the results of modeling to study the influence of the main factors affecting the change in the proportionality coefficient Kgm between the actual TPR and the TPR determined by the gamma method. To improve the accuracy of determining the TPR by the gamma method, a correction model for Kgm is proposed, which takes into account the effect of nuclear fuel burnup on the change in the signal of the background wires of the SPND. Taking into account that the signal of the background wires of the SPND is inertialess with respect to the change in the neutron power of the reactor, the introduction of the method for determining the TPR by the gamma method is promising for the implementation of an additional alternative channel for generating an emergency protection signal in terms of both power and the period of the reactor.

The article presents the results of the numerical simulation of the signal formation process of the background wires of self-powered neutron detectors (SPND) under the action of gamma radiation in the VVER-1000 core using MCNP code. The validation of the MCNP model was carried out on the results of experimental determination of the current of the background wires of the SPND, obtained at three different power units with VVER-1000 during the fuel campaign. The article also proposes a new gamma-ray method for determining the thermal power of the VVER-1000 reactor (TPR) based on the signals from the background wires of the SPND. TPR is an important safety parameter of VVER-1000, therefore, increasing the accuracy of determining TPR with the introduction of an additional gamma method for its determination is an urgent task, given the plans to increase the TPR of VVER-1000. The results of the experimental determination of the VVER-1000 TPR by the traditional neutron method based on the SPND signals are presented, and problematic issues regarding the error in determining the TPR by the neutron method are pointed out. The article presents the results of modeling to study the influence of the main factors affecting the change in the proportionality coefficient Kgm between the actual TPR and the TPR determined by the gamma method. To improve the accuracy of determining the TPR by the gamma method, a correction model for Kgm is proposed, which takes into account the effect of nuclear fuel burnup on the change in the signal of the background wires of the SPND. Taking into account that the signal of the background wires of the SPND is inertialess with respect to the change in the neutron power of the reactor, the introduction of the method for determining the TPR by the gamma method is promising for the implementation of an additional alternative channel for generating an emergency protection signal in terms of both power and the period of the reactor. [ABSTRACT FROM AUTHOR]

The current global outbreaks of mpox is a unique infectious disease in the way it seems to be transmitting: it has been observed to be highly concentrated in communities of men who have sex with men (MSM) through pair formation, and also provides long lasting immunity. This framework of mostly close, prolonged contact spreading a disease that admits immunity after infection is unlike similar infections which either offer little to no immunity post-infection or are lifelong infections. This creates the need for a new model framework that incorporates pair formation structure with recovery. While seemingly a straight forward model, we show how new dynamics arise from the combination of pair formation and recovery that are not present in a standard model with recovery and also not present in a pair formation model without recovery. We see that the combination of these two properties allows for waves of infection that are not seen in a standard SIR model. These dynamics suggest that outbreaks of mpox around the world may require special attention from public health. We also derive a reproduction number for this model and estimate the reproduction number of human mpox to be ≈2.3 using global and Canadian data. The expression derived for R0 can help estimate key parameters for diseases transmission and public health interventions and compare to equivalent models without pair formation.

In the genus Blepharisma, reproductive isolation between different species appears to be established at least by two barriers: (1) a mating pheromone, i.e., gamone 1, and (2) a factor involved in pair formation. Using four species, we experimentally investigated other potential barriers to interspecific conjugation in Blepharisma, as well as the first and second barriers. Cell-free fluid from type I cells (CFF1) of B. americanum had no effect on B. undulans, B. japonicum, or B. stoltei. Type II cells of B. americanum responded to CFF1 from B. americanum but not to CFF1 from B. undulans, B. japonicum, or B. stoltei. Gamone 1, therefore, seems to be the first reproductive barrier (with the inclusion of B. americanum species [megakaryotype 3]) as reported previously. In pretreated cells with complementary gamones in B. undulans and B. americanum, inter-species pair formation was rare, but pair formation between B. americanum and B. japonicum and between B. americanum and B. stoltei occurred at relatively high frequency. Most of the inter-species B. americanum–B. stoltei pairs underwent nuclear changes specific to conjugation. No significant difference was observed between the intra- and inter-species pairs over the time course of the nuclear changes, but the percentage of abnormal cells was higher in inter-species pairs than in intra-species pairs, and no progenies were produced by inter-species pairs. These results suggest a third barrier or step, in addition to the first and second ones, in nuclear changes after pair formation that prevents interspecific conjugation in Blepharisma. [ABSTRACT FROM AUTHOR]

In this paper, we propose a time-delayed model of West Nile virus with periodic extrinsic incubation period (EIP) and mosquito demographics including stage-structure, pair formation and intraspecific competition. We define two quantities Rmin and Rmax for mosquito population and the basic reproduction number R0 for our model. It is shown that the threshold dynamics are determined by these three parameters: (i) if Rmax < 1, the mosquito population will not survive; (ii) if Rmin > 1 and R0 < 1, then WNv disease will go extinct; (iii) if Rmin > 1 and R0 > 1, then the disease will persist. Numerically, we simulate the long-term behaviors of solutions and reveal the inuences of key model parameters on the disease transmission. A new finding is that R0 is non-monotone with respect to the fraction of the aquatic mosquitoes maturing into adult male mosquitoes, which can help us implement more effective control strategies. Besides we observe that using the time-averaged EIP has the possibility of underestimating the infection risk. [ABSTRACT FROM AUTHOR]

This article shows how to apply results of chemical reaction network theory (CRNT) to prove uniqueness and stability of a positive equilibrium for pairs/groups distributional dynamics that arise in game theoretic models. Evolutionary game theory assumes that individuals accrue their fitness through interactions with other individuals. When there are two or more different strategies in the population, this theory assumes that pairs (groups) are formed instantaneously and randomly so that the corresponding pairs (groups) distribution is described by the Hardy-Weinberg (binomial) distribution. If interactions times are phenotype dependent the Hardy-Weinberg distribution does not apply. Even if it becomes impossible to calculate the pairs/groups distribution analytically we show that CRNT is a general tool that is very useful to prove not only existence of the equilibrium, but also its stability. In this article, we apply CRNT to pair formation model that arises in two player games (e.g., Hawk-Dove, Prisoner's Dilemma game), to group formation that arises, e.g., in Public Goods Game, and to distribution of a single population in patchy environments. We also show by generalizing the Battle of the Sexes game that the methodology does not always apply. [ABSTRACT FROM AUTHOR]

A considerable body of research within the interaction framework (Long, 1996) has centred on the language-related episodes (LREs) which occur when learners topicalize a specific linguistic item while they are engaged in meaning-focused tasks. Several studies have shown that the production of LREs may be influenced by the proficiency level of the learners (Kim & McDonough, 2008; Leeser, 2004). Sociocultural theory (Lantolf & Appel, 1994) has also explored collaborative work and the effect that pairing learners with the same proficiency levels or different patterns of interaction (Storch, 2002) has on the production of LREs (e.g., Mozaffari, 2017; Storch & Aldosari 2013), but little research has compared the effect of the pair formation method (student-selected vs. proficiency-matched) on young learners’ production of LREs and pair dynamics. This study compares young CLIL learners (aged 10-12) in student-selected and proficiency-matched pairs in task-based interaction. Results indicate that learners produce more meaning-based than form-based LREs, regardless of their pair formation method. The percentage of meaning-based LREs which are resolved accurately is much higher in proficiency-matched dyads than in student-selected ones. As for the patterns of interaction (Storch, 2002), the dynamics of proficiency-matched dyads are of a more collaborative nature than those of self-selected pairs.

In the genus Blepharisma, reproductive isolation between different species appears to be established at least by two barriers: (1) a mating pheromone, i.e., gamone 1, and (2) a factor involved in pair formation. Using four species, we experimentally investigated other potential barriers to interspecific conjugation in Blepharisma, as well as the first and second barriers. Cell-free fluid from type I cells (CFF1) of B. americanum had no effect on B. undulans, B. japonicum, or B. stoltei. Type II cells of B. americanum responded to CFF1 from B. americanum but not to CFF1 from B. undulans, B. japonicum, or B. stoltei. Gamone 1, therefore, seems to be the first reproductive barrier (with the inclusion of B. americanum species [megakaryotype 3]) as reported previously. In pretreated cells with complementary gamones in B. undulans and B. americanum, inter-species pair formation was rare, but pair formation between B. americanum and B. japonicum and between B. americanum and B. stoltei occurred at relatively high frequency. Most of the inter-species B. americanum–B. stoltei pairs underwent nuclear changes specific to conjugation. No significant difference was observed between the intra- and inter-species pairs over the time course of the nuclear changes, but the percentage of abnormal cells was higher in inter-species pairs than in intra-species pairs, and no progenies were produced by inter-species pairs. These results suggest a third barrier or step, in addition to the first and second ones, in nuclear changes after pair formation that prevents interspecific conjugation in Blepharisma.

Flat-band systems are ideal model systems to study strong correlations. In a large class of one or two dimensional bosonic systems with a lowest flat-band it has been shown that at a critical density the ground states are Wigner crystals. Under very special conditions it has been shown that pair formation occurs if one adds another particle to the system. The present paper extends this result to a much larger class of lattices and to a much broader region in the parameter space. Further, a lower bound for the energy gap between these pair states and the rest of the spectrum is established. The pair states are dominated by a subspace spanned by states containing a compactly localised pair. Overall, this strongly suggests localised pair formation in the ground states of the broad class of flat-band systems and rigorously proves it for some of the graphs in it, including the inhomogeneous chequerboard chain as well as two novel examples of regular two dimensional graphs. Physically, this means that the Wigner crystal remains intact if one adds a particle to it. [ABSTRACT FROM AUTHOR]

The 'wintering strategy hypothesis' predicts that the body mass of long-distance migratory dabbling ducks is low in early winter, after autumn migration, increases in mid-winter and decreases again in late winter because of the high energetic demands of the pairing period. However, this hypothesis is assumed rather than demonstrated, since very few studies have examined these predictions. Here, we tested the theory by examining changes in size-corrected body mass (Scaled Mass Index, SMI) in Northern Pintails Anas acuta wintering at rice fields of Extremadura, a key site in Southern Europe. In both females and males, SMI increased with rainfall and deceased with fasting time, peaking in midwinter and decreasing in late winter. Northern Pintails leaving Extremadura cover between 2600 and 5600 km to reach their breeding grounds and use a number of stopover sites during their northward migration. Together, our findings support the wintering strategy hypothesis and suggest that Northern Pintails wintering in Southern Europe follow an energy-minimizing migration strategy (i.e. taking advantage of the food stock found along the route and adaptively varying fat reserves in relation to the distance to cover). We discuss that this may enable them to spend more energy and time on activities such as moulting and pairing. [ABSTRACT FROM AUTHOR]

Pair formation in ducks is thought to be influenced by the acquisition of breeding plumage, the occurrence of courtship display, or both. We examined the frequency of pair formation in Mallard (Anas platyrhynchos), Green-winged Teal (Anas crecca carolinensis), and Northern Shoveler (Spatula clypeata) in the central valley of California in relation to the frequencies of male attainment of breeding plumage and courtship display. Predictions related to two hypotheses are: (1) the timing of pair formation is directly related to the attainment of breeding (definitive alternate) plumage by males, and (2) frequencies of courtship display are highest during pair formation. Most female Mallard were paired by the end of October, with >80% in pairs by early December. Of Northern Shoveler, 90% were paired by early January and 90% of female Green-winged Teal were paired by early February. The highest rates of courtship display by Mallard were observed during October through November, by Northern Shoveler in November, and by Green-winged Teal in November through January. Courtship display was, therefore, relatively frequent at the same time as pair formation for all three species. Northern Shoveler spent less time in courtship display than the other two species. Most (90%) male Mallard had acquired alternate plumage by mid-November, Northern Shoveler by early February, and Green-winged Teal by mid-December. Thus, timing of pair formation coincided with timing of attainment of breeding plumage in Mallard and Green-winged Teal but not Northern Shoveler. [ABSTRACT FROM AUTHOR]

Vibrational pest management techniques involve the manipulation of the mating behaviour of the target species. Development of such techniques require a deep understanding of the pair formation process. Two types of bioassays were conducted to determine whether a vibrational disruptive approach could be used for Bactericera cockerelli. First, we conducted trials with either single individuals or pairs of a male and a female to ascertain whether B. cockerelli uses vibrational signals to achieve mating. Second, playback trials were conducted using two different female signals to manipulate the behaviour of males. Signals emitted during the trials were recorded using a laser vibrometer from the surface of a leaf where either single individuals or pairs of B. cockerelli were released. We described the communication phases that led to mating and the associated male and female signals. Pair formation started with a male call followed by a female response, which established a vibrational duet. During the female reply, the male searched for the female without emitting vibrational signals. Mating could be achieved if the male could maintain the female replies and reach her. In the playback trials, two different female playbacks attracted males to the signal source. Furthermore, males stimulated with female playbacks spent more time near the source of the signal than insects in the silent control group. We concluded that the B. cockerelli mating behaviour relies on vibrational signals and is potentially susceptible to vibrational manipulation, thus a future vibrational management technique could be developed to monitor or control this species. [ABSTRACT FROM AUTHOR]

A considerable body of research within the interaction framework (Long, 1996) has centred on the language-related episodes (LREs) which occur when learners topicalize a specific linguistic item while they are engaged in meaning- focused tasks. Several studies have shown that the production of LREs may be influenced by the proficiency level of the learners (Kim & McDonough, 2008; Leeser, 2004). Sociocultural theory (Lantolf & Appel, 1994) has also explored collaborative work and the effect that pairing learners with the same proficiency levels or different patterns of interaction (Storch, 2002) has on the production of LREs (e.g., Mozaffari, 2017; Storch & Aldosari 2013), but little research has compared the effect of the pair formation method (student-selected vs. proficiency-matched) on young learners' production of LREs and pair dynamics. This study compares young CLIL learners (aged 10-12) in student- selected and proficiency-matched pairs in task-based interaction. Results indicate that learners produce more meaning-based than form-based LREs, regardless of their pair formation method. The percentage of meaning-based LREs which are resolved accurately is much higher in proficiency-matched dyads than in student-selected ones. As for the patterns of interaction (Storch, 2002), the dynamics of proficiency-matched dyads are of a more collaborative nature than those of self-selected pairs. [ABSTRACT FROM AUTHOR]

Social relationships can have important fitness consequences. Although there is increasing evidence that social relationships carry over across contexts, few studies have investigated whether relationships formed early in life are carried over to adulthood. For example, juveniles of monogamous species go through a major life history stage transition, pair formation, during which the pair bond becomes a central unit of the social organization. At present, it remains unclear whether pair members retain their early life relationships after pair formation. We investigated whether same-sex associations formed early in life carry over into adulthood and whether carryover was dependent on season, in a monogamous species. We also investigated the role of familiarity, genetic relatedness and aggression on the perseverance of social associations. We studied the social structure before and after pair formation in captive barnacle geese, Branta leucopsis , a highly social, long-lived, monogamous species. We constructed association networks of groups of geese before pair formation, during the subsequent breeding season and in the following wintering season. Next, we studied how these associations carried over during seasonal changes. We found that early life associations in females were lost during the breeding season but resurfaced during the subsequent wintering season. In males, the early life associations persisted across both seasons. Association persistence was not mediated by genetic relatedness or familiarity. The high level of aggressiveness of males, but not females, in the breeding season suggests that males may have played a key role in shaping both their own social environment and that of their partners. We show that early life social relationships can be maintained well into later life. Such relationships can be sustained even if they are temporarily disrupted, for example due to reproductive behaviour. Our findings therefore highlight that the early life social environment can have lifelong consequences for individuals' social environment. • Few studies have investigated whether early life bonds carry over into adulthood. • We studied the maintenance of early life bonds after pair formation in geese. • In females early life bonds were lost during breeding but resurfaced during winter. • In males the early life bonds persisted across both seasons. • Our study shows that early life bonds can have lifelong consequences. [ABSTRACT FROM AUTHOR]

In this paper a mathematical model is formulated to study transmission dynamics of West Nile virus (WNv), which incorporates mosquito demographics including pair formation, metamorphic stages and intraspecific competition. The global behaviors of the model are obtained from a geometric approach and theory of monotone dynamics, even though bistability is present due to backward bifurcation. It turns out that the model can be investigated through two auxiliary subsystem, which are cooperative and K-competitive, respectively. Together with implement of compound matrices and Poincaré–Bendixson theorem, a thorough classification of dynamics of the full model is characterized by mosquito reproduction number R M , WNv reproduction number R 0 and a bistability subthreshold R 0 c . The theoretical results show that if R M is not greater than 1, mosquitoes will not survive, and the WNv will die out; if R M is greater than 1, then mosquitoes will persist, and disease may prevail or vanish depending on basin of attraction of the local attractors which are singletons. Our method in this paper can be applied to other mosquito-borne diseases such as malaria, dengue fever which have a similar monotonicity. [ABSTRACT FROM AUTHOR]

We explore the transmission process for sexually transmitted diseases (STDs). We derive the classical frequency-dependent incidence mechanistically from a pair-formation model, using an approximation that applies to populations with rapid pairing dynamics (such as core groups or non-pair-bonding animals). This mechanistic derivation provides a framework to assess how accurately frequency-dependent incidence portrays the pair-based transmission known to underlie STD dynamics. This accuracy depends strongly on the disease being studied: frequency-dependent formulations are more suitable for chronic less-transmissible infections than for transient highly transmissible infections. Our results thus support earlier proposals to divide STDs into these two functional classes, and we suggest guidelines to help assess under what conditions each class can be appropriately modelled using frequency-dependent incidence. We then extend the derivation to include situations where infected individuals exhibit altered pairing behaviour. For four cases of increasing behavioural complexity, analytic expressions are presented for the generalized frequency-dependent incidence rate, basic reproductive number (R0) and steady-state prevalence (i∞) of an epidemic. The expression for R0is identical for all cases, giving refined insights into determinants of invasibility of STDs. Potentially significant effects of infection-induced changes in contact behaviour are illustrated by simulating epidemics of bacterial and viral STDs. We discuss the application of our results to STDs (in humans and animals) and other infectious diseases.

We explore the transmission process for sexually transmitted diseases (STDs). We derive the classical frequency-dependent incidence mechanistically from a pair-formation model, using an approximation that applies to populations with rapid pairing dynamics (such as core groups or non-pair-bonding animals). This mechanistic derivation provides a framework to assess how accurately frequency-dependent incidence portrays the pair-based transmission known to underlie STD dynamics. This accuracy depends strongly on the disease being studied: frequency-dependent formulations are more suitable for chronic less-transmissible infections than for transient highly transmissible infections. Our results thus support earlier proposals to divide STDs into these two functional classes, and we suggest guidelines to help assess under what conditions each class can be appropriately modelled using frequency-dependent incidence. We then extend the derivation to include situations where infected individuals exhibit altered pairing behaviour. For four cases of increasing behavioural complexity, analytic expressions are presented for the generalized frequency-dependent incidence rate, basic reproductive number (R-0) and steady-state prevalence (i(infinity)) of an epidemic. The expression for R-0 is identical for all cases, giving refined insights into determinants of invasibility of STDs. Potentially significant effects of infection-induced changes in contact behaviour are illustrated by simulating epidemics of bacterial and viral STDs. We discuss the application of our results to STDs (in humans and animals) and other infectious diseases.

Researchers and policy makers have argued that long-duration concurrent relationships promote the spread of HIV. The concurrency hypothesis proposes that concurrent partnering, particularly as manifested in formal and informal polygyny, is a primary contributor to the spread of HIV in sub-Saharan Africa. We investigate claims that agent-based models of concurrent partnering support this hypothesis. Specifically, we explore how assumptions about the duration and network structure of sexual partnerships affect the results of agent-based models of HIV propagation. We offer new support for the contention that long-duration concurrent partnering can be protective against HIV transmission rather than promoting it. Additionally, we argue that the focus on concurrency has misdirected attention away from the key role of exclusivity. [ABSTRACT FROM AUTHOR]

Year-round behavioral observations and surveys were used to investigate the temporal dynamics of life history events and associated variation in behavioral activities of the endangered, island-endemic Hawaiian Duck (Anas wyvilliana) on Kaua'i, Hawai'i, USA. Although breeding activity occurred throughout the year, backdated brood observations (n = 67) revealed that birds initiated 94% of nests during the 9-month period from September through May, their peak nesting season. A greater proportion of females (n = 149) were paired during the peak nesting season (75%) than the off-peak season (48%). Behavioral patterns (n = 984; 329 hr) differed between seasons for males but not for females. Males allocated more time to vigilance and less time to foraging during the peak nesting season than the off-peak season. Activity budgets also differed between sexes, but only during the peak nesting season. During this period, females spent more time foraging than males, whereas males allocated more time to vigilance, locomotion, and social activities. Current management objectives for the Hawaiian Duck aim to provide resources for multiple life history stages concurrently throughout the year, and although this approach is largely appropriate, our results suggest refinements in the timing of certain activities (e.g., managing nesting habitat to be available during September-May). [ABSTRACT FROM AUTHOR]

Highlights • A new approach to the theory of two-player bimatrix evolutionary games where pairs are formed by the mass action principle is developed and compared to models with instantaneous pair formation. • This theory explicitly considers the duration of interactions between the two players and their status as singles between interactions. • When applied to the bimatrix Hawk-Dove game (called the Owner-Intruder game), this theory shows that differences in interaction times lead to new interior and boundary Nash equilibria. • Existence and stability of these Nash equilibria depend on whether pairing is instantaneous or not. Abstract Classic bimatrix games, that are based on pair-wise interactions between two opponents in two different roles, do not consider the effect that interaction duration has on payoffs. However, interactions between different strategies often take different amounts of time. In this article, we further develop a new approach to an old idea that opportunity costs lost while engaged in an interaction affect individual fitness. We consider two scenarios: (i) individuals pair instantaneously so that there are no searchers, and (ii) searching for a partner takes positive time and populations consist of a mixture of singles and pairs. We describe pair dynamics and calculate fitnesses of each strategy for a two-strategy bimatrix game that includes interaction times. Assuming that distribution of pairs (and singles) evolves on a faster time scale than evolutionary dynamics described by the replicator equation, we analyze the Nash equilibria (NE) of the time-constrained game. This general approach is then applied to the Owner–Intruder bimatrix game where the two strategies are Hawk and Dove in both roles. While the classic Owner–Intruder game has at most one interior NE and it is unstable with respect to replicator dynamics, differences in pair duration change this prediction in that up to four interior NE may exist with their stability depending on whether pairing is instantaneous or not. The classic game has either one (all Hawk) or two ((Hawk,Dove) and (Dove,Hawk)) stable boundary NE. When interaction times are included, other combinations of stable boundary NE are possible. For example, (Dove,Dove), (Dove,Hawk), or (Hawk,Dove) can be the unique (stable) NE if interaction time between two Doves is short compared to some other interactions involving Doves. [ABSTRACT FROM AUTHOR]

Game theoretic models of evolution such as the Hawk–Dove game assume that individuals gain fitness (which is a proxy of the per capita population growth rate) in pair-wise contests only. These models assume that the equilibrium distribution of phenotypes involved (e.g., Hawks and Doves) in the population is given by the Hardy–Weinberg law, which is based on instantaneous, random pair formation. On the other hand, models of population dynamics do not consider pairs, newborns are produced by singles, and interactions between phenotypes or species are described by the mass action principle. This article links game theoretic and population approaches. It shows that combining distribution dynamics with population dynamics can lead to stable coexistence of Hawk and Dove population numbers in models that do not assume a priori that fitness is negative density dependent. Our analysis shows clearly that the interior Nash equilibrium of the Hawk and Dove model depends both on population size and on interaction times between different phenotypes in the population. This raises the question of the applicability of classic evolutionary game theory that requires all interactions take the same amount of time and that all single individuals have the same payoff per unit of time, to real populations. Furthermore, by separating individual fitness into birth and death effects on singles and pairs, it is shown that stable coexistence in these models depends on the time-scale of the distribution dynamics relative to the population dynamics. When explicit density-dependent fitness is included through competition over a limited resource, the combined dynamics of the Hawk–Dove model often lead to Dove extinction no matter how costly fighting is for Hawk pairs. [ABSTRACT FROM AUTHOR]

Hard core bosons in a large class of one or two dimensional flat band systems have an upper critical density, below which the ground states can be described completely. At the critical density, the ground states are Wigner crystals. If one adds a particle to the system at the critical density, the ground state and the low lying multi particle states of the system can be described as a Wigner crystal with an additional pair of particles. The energy band for the pair is separated from the rest of the multi-particle spectrum. The proofs use a Gerschgorin type of argument for block diagonally dominant matrices. In certain one-dimensional or tree-like structures one can show that the pair is localised, for example in the chequerboard chain. For this one-dimensional system with periodic boundary condition the energy band for the pair is flat, the pair is localised. [ABSTRACT FROM AUTHOR]

In this paper, the agent-based simulation model of sexual selection and pair formation mechanisms is proposed. Sexual selection is a mechanism that occurs when the numbers of individuals of both sexes are almost identical, while reproduction costs for one of the sexes are much higher. The mechanism of creating pairs allows individuals to form stable, reproducing pairs. Simulation experiments carried out using the proposed agent-based model, and several fitness landscapes were aimed at verifying whether sexual selection and the mechanism of pair formation can trigger sympatric speciation and whether they can promote and maintain population diversity. Experiments were mainly focused on the mechanism of pair formation and its impact on speciation and population diversity. Results of conducted experiments show that sexual selection can start speciation processes and maintain the population diversity. The mechanism of creating pairs, when it occurs along with sexual selection, has a significant impact on the course of speciation and maintenance of population diversity. [ABSTRACT FROM AUTHOR]

The current global outbreaks of mpox is a unique infectious disease in the way it seems to be transmitting: it has been observed to be highly concentrated in communities of men who have sex with men (MSM) through pair formation, and also provides long lasting immunity. This framework of mostly close, prolonged contact spreading a disease that admits immunity after infection is unlike similar infections which either offer little to no immunity post-infection or are lifelong infections. This creates the need for a new model framework that incorporates pair formation structure with recovery. While seemingly a straight forward model, we show how new dynamics arise from the combination of pair formation and recovery that are not present in a standard model with recovery and also not present in a pair formation model without recovery. We see that the combination of these two properties allows for waves of infection that are not seen in a standard SIR model. These dynamics suggest that outbreaks of mpox around the world may require special attention from public health. We also derive a reproduction number for this model and estimate the reproduction number of human mpox to be ≈ 2. 3 using global and Canadian data. The expression derived for R 0 can help estimate key parameters for diseases transmission and public health interventions and compare to equivalent models without pair formation. • A novel model framework of pair formation with recovery is developed and analyzed. • A comparison is made between features of this pair formation model and an SIR model. • A basic reproduction number is computed for the model. • The model is parametrized by the 2022 mpox outbreak. [ABSTRACT FROM AUTHOR]

Pair bonds can provide social benefits to long-term monogamous species alongside their benefits for reproduction. However, little is known about when these bonds form, in particular how long they are present before breeding. Previous studies of pair formation in long-term monogamous birds have been rather data-limited, but for many migratory birds they report pair formation on the wintering grounds. We provide the first systematic investigation of prebreeding association patterns of long-term monogamous pairs by examining entire life histories based on tracking data of migratory whooping cranes, Grus americana . We found that a substantial portion (62%) of breeding pairs started associating at least 12 months before first breeding, with 16 of 58 breeding pairs beginning to associate over 2 years before first breeding. For most pairs, these associations with future breeding partners also became unique and distinguishable from association patterns with nonpartner individuals 12 months before first breeding. In addition, 60% of pair associations began before at least one partner had reached nominal sexual maturity. Most pairs began associating in the late spring upon arrival at the summer grounds, while associations beginning at other times of the year were rare. Patterns in the associations of pairs prior to breeding can point to the potential benefits of prebreeding relationships, for instance providing support in competitive interactions or increasing partner familiarity. [ABSTRACT FROM AUTHOR]

The aim of this study based on personal field observations and capture (8407 individuals) and recapture (2691 individuals) data was to broaden the knowledge about the pair formation strategy of the Bearded Reedling Panurus biarmicus. A male and a female bird were considered a pair if they were not further than 1 meter from each other in the net; or if they were further than 1 meter, but they have behaved as pairs before the capture. Our results partially confirm the previous knowledge about the pair formation of juveniles; furthermore, we proved that 63% of those pairs that were recaptured once consisted of juvenile males and females even before the summer complete moult. 30% of all the pairs were formed of adult males and adult females and only 7% were of juvenile-adult combination. 78% of the birds captured as pairs and recaptured at least once kept the pair bond from the time before the moult until the time of roaming, while 22% changed their pairs during the same period. [ABSTRACT FROM AUTHOR]

Stochastic encounter-mating (SEM) models describe monogamous permanent pair formation in finite zoological populations of multitype females and males. In this paper we study SEM models with Poisson firing times. First, we prove that the model enjoys a fluid limit as the population size diverges, that is, the stochastic dynamics converges to a deterministic system governed by coupled ordinary differential equations (ODEs). Then we convert these ODEs to the well-known Lotka–Volterra and replicator equations from population dynamics. Next, under the so-called fine balance condition which characterizes panmixia, we solve the corresponding replicator equations and give an exact expression for the fluid limit. Finally, we consider the case with two types of female and male. Without the fine balance assumption, but under certain symmetry conditions, we give an explicit formula for the limiting mating pattern, and then use it to characterize assortative mating. [ABSTRACT FROM AUTHOR]

Enclosure theorems are derived for homogeneous bounded order-preserving operators and illustrated for operators involving pair-formation functions introduced by Karl-Peter Hadeler in the late 1980s. They are applied to a basic discrete-time two-sex population model and to the relation between the basic turnover number and the basic reproduction number. [ABSTRACT FROM AUTHOR]

We propose a new model of permanent monogamous pair formation in zoological populations with multiple types of females and males. According to this model, animals randomly encounter members of the opposite sex at their so-called firing times to form temporary pairs which then become permanent if mating happens. Given the distributions of the firing times and the mating preferences upon encounter, we analyze the contingency table of permanent pair types in three cases: (i) definite mating upon encounter; (ii) Poisson firing times; and (iii) Bernoulli firing times. In the first case, the contingency table has a multiple hypergeometric distribution which implies panmixia. The other two cases generalize the encounter-mating models of Gimelfarb (Am. Nat. 131(6):865-884, 1988) who gives conditions that he conjectures to be sufficient for panmixia. We formulate adaptations of his conditions and prove that they not only characterize panmixia but also allow us to reduce the model to the first case by changing its underlying parameters. Finally, when there are only two types of females and males, we provide a full characterization of panmixia, homogamy and heterogamy. [ABSTRACT FROM AUTHOR]

Two most influential models of evolutionary game theory are the Hawk-Dove and Prisoner's dilemma models. The Hawk-Dove model explains evolution of aggressiveness, predicting individuals should be aggressive when the cost of fighting is lower than its benefit. As the cost of aggressiveness increases and outweighs benefits, aggressiveness in the population should decrease. Similarly, the Prisoner's dilemma models evolution of cooperation. It predicts that individuals should never cooperate despite cooperation leading to a higher collective fitness than defection. The question is then what are the conditions under which cooperation evolves? These classic matrix games, which are based on pair-wise interactions between two opponents with player payoffs given in matrix form, do not consider the effect that conflict duration has on payoffs. However, interactions between different strategies often take different amounts of time. In this article, we develop a new approach to an old idea that opportunity costs lost while engaged in an interaction affect individual fitness. When applied to the Hawk-Dove and Prisoner's dilemma, our theory that incorporates general interaction times leads to qualitatively different predictions. In particular, not all individuals will behave as Hawks when fighting cost is lower than benefit, and cooperation will evolve in the Prisoner's dilemma. [ABSTRACT FROM AUTHOR]

In this paper, the agent-based simulation model of sexual selection and pair formation mechanisms is proposed. Sexual selection is a mechanism that occurs when the numbers of individuals of both sexes are almost identical, while reproduction costs for one of the sexes are much higher. The mechanism of creating pairs allows individuals to form stable, reproducing pairs. Simulation experiments carried out using the proposed agent-based model, and several fitness landscapes were aimed at verifying whether sexual selection and the mechanism of pair formation can trigger sympatric speciation and whether they can promote and maintain population diversity. Experiments were mainly focused on the mechanism of pair formation and its impact on speciation and population diversity. Results of conducted experiments show that sexual selection can start speciation processes and maintain the population diversity. The mechanism of creating pairs, when it occurs along with sexual selection, has a significant impact on the course of speciation and maintenance of population diversity.

The present study examined pair formation, spatial pattern of home range and spatial variation in density, size and social status of blotched foxface Siganus unimaculatus (family Siganidae) on an Okinawan coral reef. Of 32 pairs sampled for sexing, 31 (96.9%) were heterosexual and showed size-assortative pairing. Developed ovaries were found in April and July, whereas oocytes were immature in August, September and February. Heterosexual pairing was found in both reproductive and non-reproductive periods. Home range size tended to be positively related to fork length (FL). The degree of home range overlap for same size class pairs was smaller than that for different size class pairs. The intraspecific behavior when two pairs approached each other was categorized as ‘attack,’ ‘agonistic display’ and ‘no interactions,’ and the frequency of agonistic behaviors (“attack” or “agonistic display”) was significantly greater than “no interactions.” Underwater observations at a seagrass bed, a rocky reef flat and a sheltered reef slope revealed that the mean FL was significantly smaller at the sheltered reef slope (4–13 cm) than at the rocky reef flat (>13 cm). No individuals were found in the seagrass bed. Most individuals less than 6 cm FL were solitary, whereas most individuals over 7 cm FL were paired. Density was significantly greater on the sheltered reef slope than on the rocky reef flat.

Adult rabbitfishes (Siganidae) differ from most other herbivorous coral reef fishes by forming stable pair bonds throughout their adult lives. However, little is known about the early life stages of rabbitfishes, and no quantitative evidence regarding the ontogeny of pairing behaviour exists to date. This study describes the abundance, distribution and ontogeny of social associations in juvenile rabbitfishes on the mid-shelf reefs around Lizard Island, Great Barrier Reef, Australia. Using underwater visual censuses, we surveyed an area of 5728 m2across three distinct habitat types, revealing that the abundance of juveniles varies significantly among species, size class and exposure level. Furthermore, we demonstrate a pronounced ontogenetic shift in the social associations of juveniles ofSiganus doliatusandSiganus corallinus, changing from primarily solitary individuals in the smallest size class (<50 mm) to predominantly paired individuals in the larger size classes (50–100 mm and 100–150 mm). In this context, we report the presence of several mixed-species pairs of rabbitfishes, providing the first evidence for this behaviour within the family. This supports previous research, which posits that there are strong ecological drivers, rather than a solely reproductive basis, for pairing behaviour in rabbitfishes. Based on our results, we suggest that further exploration of the ecology of early life stages of herbivorous reef fishes will increase our knowledge about ecological processes on coral reefs. [ABSTRACT FROM PUBLISHER]