Encounter Probability Research Articles

Stellar encounters with giant molecular clouds

ABSTRACTGiant molecular clouds (GMCs) are believed to affect the biospheres of planets as their host star passes through them. We simulate the trajectories of stars and GMCs in the Galaxy and determine how often stars pass through GMCs. We find a strong decreasing dependence with Galactocentric radius, and with the velocity perpendicular to the Galactic plane, V$\mathrm{ z}$. The XY-component of the kinematic heating of stars was shown to not affect the GMC hit rate, unlike the Z-dependence (V$\mathrm{ z}$) implies that stars hit fewer GMCs as they age. GMCs are locations of star formation, therefore we also determine how often stars pass near supernovae. For the supernovae the decrease with V$\mathrm{ z}$ is steeper as how fast the star passes through the GMC determines the probability of a supernova encounter. We then integrate a set of Sun-like trajectories to see the implications for the Sun. We find that the Sun hits 1.6 ± 1.3 GMCs per Gyr which results in 1.5 ± 1.1 or (with correction for clustering) 0.8 ± 0.6 supernova closer than 10 pc per Gyr. The different the supernova frequencies are from whether one considers multiple supernovae per GMC crossing (few Myr) as separate events. We then discuss the effect of the GMC hits on the Oort cloud, and the Earth’s climate due to accretion, we also discuss the records of distant supernova. Finally, we determine Galactic Habitable Zone using our model. For the thin disc, we find it to lie between 5.8 and 8.7 kpc and for the thick disc to lie between 4.5 and 7.7 kpc.

Distance-Decay Effect in Probabilistic Time Geography for Random Encounter

Probabilistic time geography uses a fixed distance threshold for the definition of the encounter events of moving objects. However, because of the distance-decay effect, different distances within the fixed threshold ensure that the encounter events do not always have the same possibility, and, therefore, the quantitative probabilistic time geography analysis needs to consider the actual distance-decay coefficient (DDC). Thus, this paper introduces the DDC and proposes a new encounter probability measure model that takes into account the distance-decay effect. Given two positions of a pair of moving objects, the traditional encounter probability model is that if the distance between the two positions does not exceed a given threshold, the encounter event may occur, and its probability is equal to the product of the probabilities of the two moving objects in their respective positions. Furthermore, the probability of the encounter at two given positions is multiplied by the DDC in the proposed model, in order to express the influence of the distance-decay effect on the encounter probability. Finally, the validity of the proposed model is verified by an experiment, which uses the tracking data of wild zebras to calculate the encounter probability, and compares it with the former method.

Probability Analysis and Control of River Runoff–sediment Characteristics based on Pair-Copula Functions: The Case of the Weihe River and Jinghe River

Analyzing the encounter frequency of high–low runoff and sediment yield is important for the appropriate dispatching of runoff–sediment resources, as well as river regulation. However, there have been no reports on the utilization of the pair-copula function in analyzing the runoff–sediment characteristics from a probabilistic perspective and conducting probability control on the runoff–sediment yields of different hydrologic stations. This paper builds marginal distribution functions on the basis of kernel distribution theory. In addition, this paper builds the joint distribution functions through pair-copula functions in order to analyze the encounter probability and the compensation characteristics of high–low runoff and sediment at different stations on the Weihe River in China, as well as the origins of runoff–sediment, to conduct probability control of river runoff–sediment resource allocation. The results show that, in different periods, the synchronous probability of high–low runoff of the Weihe River’s Xianyang and Huaxian Stations, and the Jinghe River’s Zhangjiashan Station differ, while that of high–low sediment at the three stations changes little—remaining at around 54%. Therefore, the sediment and runoff of the Weihe River apparently have different origins. In years of high and low runoff, if the runoffs of the Xianyang and Zhangjiashan Stations can be kept within a certain range, then the runoff of the Huaxian Station will be in a particular range, at a certain probability. Sediment at the Huaxian Station can be controlled, in a similar way. These results are of great significance for the water and sediment management department of the Weihe river, in order to reasonably allocate water and sediment resources.

Marine litter on the Baltic seafloor collected by the international fish-trawl survey

Marine litter is a global concern. Since most of the litter sinks, understanding the composition of benthic marine litter is crucial for addressing this concern. However, high costs of seafloor monitoring inhibit such understanding. Consequently, benthic marine litter in the Baltic Sea has not been comprehensively addressed yet. Here we present data from 2377 hauls, which collected 6828 litter items and 2412 kg on the Baltic seafloor during six years of the Baltic International Trawl Survey (BITS) by seven nations. Our results show lower percentages of plastic (35%) than the widely cited world average (70%) and less fishery-originated litter (2.2–5.6%) than was previously reported for the Baltic Sea (4–24%). Natural products, mostly residuals of burnt coal, were identified as the most common litter category (42–57%) and were largely ignored in the past. Our results highlight the importance of using several evaluation metrics, particularly number of items, weight and encounter probability.

Size Selectivity of Sampling Gears Used to Sample Kokanee

AbstractKokanee Oncorhynchus nerka provide valued recreational fisheries and also serve as a prey resource for economically, socially, and ecologically important fishes. As such, management of kokanee is a major focus of natural resource agencies. Kokanee are typically monitored using midwater trawls, but the interpretation of data collected using midwater trawls is difficult due to the unknown size selectivity of the gear. We sought to assess the length selectivity of midwater trawls by comparing estimates obtained from midwater trawls with estimates obtained from gill nets adjusted for size selectivity. Experimental curtain gill nets and midwater trawls were used in conjunction to sample kokanee in seven lentic systems in Idaho. The size selectivity of gill nets was estimated by accounting for the probability of encounter and the probability of retention. Estimates of size selectivity were then used to adjust the length distribution of fish sampled in gill nets. The adjusted length distribution of fish sampled in gill nets was compared with estimates obtained from midwater trawls to identify potential size selectivity of midwater trawls. A pattern of size selectivity was apparent for both sampling techniques. The average length of kokanee sampled with midwater trawls was 111 mm; whereas, kokanee sampled with gill nets had a mean length of 235 mm. Our results suggest experimental gill nets are useful for common sampling of kokanee (e.g., trend monitoring) because the gear is less size selective than midwater trawls and is adjustable for size selectivity. However, midwater trawls are likely the best gear for addressing questions associated with early life history. Overall, our results provide a better understanding of gill‐net and midwater trawl selectivity and ultimately improve the ability to sample and manage the species.

Types and species diversity of Cupressus communities in Southeast Tibet, China.

Cupressus communities are the important parts of natural forests in Southeast Tibet, with significance on plateau biodiversity conservation and ecological security. To clarify their types and plant species diversity, we analyzed species composition and diversity indices, diameter class pattern of constructive species in different communities in Milin County, Lang County and Bomi County, Southeast Tibet. The results showed that Cupressus communities could be classified into four types: C. torulosa-Lonicera lanceolate + Philadelphus tomentosus-Pteris cretica var. nervosa + Digitaria violascens community (Community1), C. gigantea-Desmodium elegans + Sophora moorcroftia-na-Tripogon filiformis + Cymbopogon distans + Orinus thoroldii community (Community2), C. gigantea-Leptodermis purdomii-Chenopodium hybridum + O. thoroldii community (Community 3), and C. gigantea-Ceratostigma minus-A. desertorum + O. thoroldii + Tribulus terrester community (Community 4). Across those four community types, Margalef index, Shannon index, Pielou index and interspecies encounter probability index all ranked with the decreasing order of Community1, Community2, Community 3 and Community 4. Diameter class pattern of the constructive species showed that many young and few middle/old individuals were within the four communities. High mortality rate occurred during the interim period from young to middle age classes. In general, populations of Cupressus plants showed a declining trend.

Interannual variation of the diet shifts and their effects on the fatness and growth of age‐0 Pacific bluefin tuna (Thunnus orientalis) off the southwestern Pacific coast of Japan

AbstractWe investigated the effect of feeding habits on the fatness (length–weight relationship (LW)) and otolith growth of age‐0 Pacific bluefin tuna (PBF) (fork length (FL) of 15.0–29.9 cm) collected off the southwestern Pacific coast of Japan from July to August during 2010–2015. The feeding rate on Clupeiformes (FRc) was substantially influenced by the path of the Kuroshio Current during early summer. We suggest that the following patterns occurred in the feeding habits of PBF. In 2012 and 2014, the short distance from the coast to the Kuroshio provided high overlap between PBF and Clupeiformes and increased the opportunity for feeding, and this pattern likely caused the observed diet shift from Crustacea to Clupeiformes by smaller PBF in the studied years than those in other years. In 2011 and 2015, the encounter probability for Clupeiformes might have been low due to the long distance to the Kuroshio Current, which led PBF to actively consume non‐Clupeiformes Teleostei. In contrast, in August 2010 and 2015, PBF did not encounter Clupeiformes or other Teleostei and may have been forced to feed on a large number of Crustacea; this effect was likely due to high water temperatures. Despite the interannual fluctuation in the timing of the diet shift and the feeding intensity (FI), these factors did not contribute to growth in length; rather, they contributed to fatness. Considering size‐dependent mortality in the larval stage, these results suggest that only fast‐growing individuals survive, even if the feeding conditions drastically change.

Green fluorescence from cnidarian hosts attracts symbiotic algae

Reef-building corals thrive in nutrient-poor marine environments because of an obligate symbiosis with photosynthetic dinoflagellates of the genus Symbiodinium Symbiosis is established in most corals through the uptake of Symbiodinium from the environment. Corals are sessile for most of their life history, whereas free-living Symbiodinium are motile; hence, a mechanism to attract Symbiodinium would greatly increase the probability of encounter between host and symbiont. Here, we examined whether corals can attract free-living motile Symbiodinium by their green fluorescence, emitted by the excitation of endogenous GFP by purple-blue light. We found that Symbiodinium have positive and negative phototaxis toward weak green and strong purple-blue light, respectively. Under light conditions that cause corals to emit green fluorescence, (e.g., strong blue light), Symbiodinium were attracted toward live coral fragments. Symbiodinium were also attracted toward an artificial green fluorescence dye with similar excitation and emission spectra to coral-GFP. In the field, more Symbiodinium were found in traps painted with a green fluorescence dye than in controls. Our results revealed a biological signaling mechanism between the coral host and its potential symbionts.

Probabilistic Model of Random Encounter in Obstacle Space

Based on probabilistic time-geography, the encounter between two moving objects is random. The quantitative analysis of the probability of encounter needs to consider the actual geographical environment. The existing encounter probability algorithm is based on homogeneous space, ignoring the wide range of obstacles and their impact on encounter events. Based on this, this paper introduces obstacle factors, proposes encounter events that are constrained by obstacles, and constructs a model of the probability of encounters of moving objects based on the influence of obstacles on visual perception with the line-of-sight view analysis principle. In realistic obstacle space, this method provides a quantitative basis for predicting the encountering possibility of two mobile objects and the largest possible encounter location. Finally, the validity of the model is verified by experimental results. The model uses part of the Wuhan digital elevation model (DEM) data to calculate the encounter probability of two moving objects on it, and analyzes the temporal and spatial distribution characteristics of these probabilities.

Incentivized Social-Aware Proactive Device Caching With User Preference Prediction

In order to offload network traffic, we design a device caching strategy by jointly considering a popularity model, social influence and incentive design in this paper. Firstly, we propose a prediction model by virtue of users' social network information to evaluate users' encounter probability. Moreover, users' content preference is predicted using users' context information. Based on these predicted values, a content placement algorithm is described provided that the users will fully cooperate to optimize system performance. Thereafter, a more practical scenario where users are selfish and unwilling to devote their resources is considered. A Stackelberg game is established between the mobile network operator (MNO) and users by providing an incentive to encourage cooperation. Device caching strategy and incentive price design are determined by analyzing the Stackelberg game and finding the Stackelberg equilibrium point. We verify the effectiveness of our prediction models utilizing real data sets. Simulation results show that the cache hit ratio can be considerably improved by exploiting social and context information. Incentive design and profit analysis are also thoroughly investigated.

Synchronous asynchronous encounter analysis of runoff between reservoirs based on Copula function

Based on goodness-of-fit test on Copula function, we got the best fitted joint distribution function of runoff between D and H reservoirs. Then we analyzed the synchronous asynchronous encounter probability of runoff. The synchronous encounter probability of runoff was 72.46%, while the asynchronous of dryness-wetness or wetness-dryness encounter probability was only 1.06% between D and H reservoirs. The results showed that the runoff conditions were not conducive to the runoff compensation. In order to satisfy the target of water supply, we should also study the reservoir optimization operation, store water in advance and exploit the reservoir regulating potentialities on flood water resources.

Assessment of the predatory capacity on mosquito larvae of Jenynsia multidentata (Anablepidae) in presence of vegetation under laboratory conditions

ABSTRACT Larvivorous fish have been studied as potential biocontrol agents of mosquito larvae and pupae through their trophic interactions. The use of native fish for mosquito control may have benefits for both aquatic biodiversity and human health. Evaluating the effect of vegetation on the predatory efficacy is fundamental to determine if this species can be used as a biocontrol agent. With the aim of evaluating Jenynsia multidentata (Jenyns, 1842) as a biocontrol agent of Culex pipiens Linnaeus, 1758, we tested its predatory capacity in the presence or absence of aquatic vegetation under laboratory conditions. Two independent experiments were conducted. Larval consumption at a density of 60 larvae (6 larvae/l) was significantly reduced with the vegetation increased. On the other hand, when the larval density was 120 (12 larvae/l), the predatory capacity of J. multidentata did not vary in the presence or absence of vegetation. This result indicated that vegetation effect on consumption could be related to prey density, since at the higher density of prey the probability of predator-prey encounter might be increased. Jenynsia multidentata is a good consumer in presence of vegetation and could be used as a potential biocontrol agent of mosquito larvae in natural environments with similar characteristics to the ones tested in these experiments.

Understanding the role of eco-evolutionary feedbacks in host-parasite coevolution

It is widely recognised that eco-evolutionary feedbacks can have important implications for evolution. However, many models of host-parasite coevolution omit eco-evolutionary feedbacks for the sake of simplicity, typically by assuming the population sizes of both species are constant. It is often difficult to determine whether the results of these models are qualitatively robust if eco-evolutionary feedbacks are included. Here, by allowing interspecific encounter probabilities to depend on population densities without otherwise varying the structure of the models, we provide a simple method that can test whether eco-evolutionary feedbacks per se affect evolutionary outcomes. Applying this approach to explicit genetic and quantitative trait models from the literature, our framework shows that qualitative changes to the outcome can be directly attributable to eco-evolutionary feedbacks. For example, shifting the dynamics between stable monomorphism or polymorphism and cycling, as well as changing the nature of the cycles. Our approach, which can be readily applied to many different models of host-parasite coevolution, offers a straightforward method for testing whether eco-evolutionary feedbacks qualitatively change coevolutionary outcomes.

Injecting drug use is an independent risk factor for reincarceration after release from prison: A prospective cohort study.

Once involved in the criminal justice system, people who inject drugs (PWID) have a high probability of multiple system encounters. Imprisonment typically fails to rehabilitate PWID, who upon return to the community are at considerable risk of returning to injecting drug use (IDU) and poor health and social outcomes. We examined the effect of IDU resumption, and a suite of other sociodemographic, criminogenic, health and behavioural indicators, on the timing of reincarceration among adults with a history of IDU following release from prison. Structured interviews were conducted with 561 PWID in Queensland, Australia prior to release from prison and approximately 1, 3 and 6 months post-release. Data were linked prospectively with correctional records and the National Death Index. Data collected at multiple time-points were treated as time-varying covariates. Kaplan-Meier survival estimates and Cox proportional hazards models were used to estimate the rate and hazards of reincarceration. Sixty-eight percent of participants (n = 350) were reincarcerated over a combined observation time of 1043.5 years, representing a rate of 33.5 per 100 person-years (95% confidence interval [CI] 30.2-37.2). Time-invariant predictors of reincarceration in PWID were: male gender (adjusted hazard ratio [AHR] = 1.62, 95% CI 1.19-2.21), older age at release (AHR = 0.97, 95% CI 0.95-1.00), previous adult (AHR = 2.00, 95% CI 1.41-2.84) or juvenile (AHR = 1.78, 95% CI 1.27-2.49) imprisonment, shorter imprisonment (≤90 days vs. >365 days, AHR = 2.09, 95% CI 1.30-3.34), release on parole (AHR = 2.29, 95% CI 1.82-2.88) and drug-related sentence (AHR = 1.84, 95% CI 1.34-2.53). Time-varying predictors included resumption of IDU (AHR = 2.04, 95% CI 1.60-2.61), unemployment (AHR = 1.53, 95% CI 1.07-2.19) and low perceived social support (AHR = 1.41, 95% CI 1.05-1.90). Very-high psychological distress at the most recent interview was protective against reincarceration (AHR = 0.65, 95% CI 0.44-0.95). Efforts to prevent resumption of IDU and address disadvantage, social inclusion and health service access in ex-prisoners through the scale-up and integration of prison-based and post-release interventions are likely to reap both public health and criminal justice benefits.

Unbundling negative and positive externalities of nature in cities: The influence of wild animals on housing prices

Proximity to nature is highly valued by urbanites, who demonstrate higher willingness to pay for housing at locations near open and green spaces. However, nature in cities can generate negative externalities as well. In this article, we illustrate the complex relationship between cities and nature and suggest that their balance is time and location specific. The article presents estimates of positive and negative externalities based on data about encounters of humans with wild animals in the city of Haifa, Israel, and residential property values nearby. The data were analysed to uncover spatial regularities and basic statistical relationships. The results reveal the presence of dominant positive externalities when the human–wild animals interaction is low, driven by proximity to open and green areas. However, in certain areas and under certain circumstances, the nuisance generated by higher probabilities of encounters with wild animals near dwelling areas is correlated with lower property prices, overcoming the positive externalities of location near natural areas.

Does fire disturbance affect ant community structure? Insights from spatial co-occurrence networks.

The coexistence of several species involves a complex mix of positive and negative interactions that can be represented as networks. As much as other ecological features, patterns of multispecies co-occurrence are susceptible to anthropogenic disturbance. In ant communities, wildfires may enhance competitive interactions by benefiting active, aggressive species, and by increasing encounter probabilities through decreased space availability. We explored ant co-occurrence patterns by analysing the macro and microscopic structure of their interaction networks in burned and unburned habitats. We built co-occurrence networks using significant aggregations and segregations between species pairs as positive and negative interactions, respectively. We described aggregate network properties and microscopic structural changes by comparing species and interactions turnover between burned and unburned sites. We found no differences in the macroscopic structure of co-occurrence networks between different fire regimes. However, we detected changes in the composition of both species and negative interactions. Interaction turnover between networks of different habitats was mostly explained by rewiring of interactions between shared species rather than by species replacement. Our results reflected changes in ant communities in response to fire although there were no changes in global structural patterns. These changes in species and negative interactions suggest modifications in species roles translated into changes in the spatial distribution of ant species. The analysis of species co-occurrence networks is a useful tool to detect and visualize patterns in ant communities and to understand the mechanisms underlying the effects of disturbance on biodiversity.

Opportunistic protocol based on social probability and resources efficiency for the intelligent and connected transportation system

In recent years, Intelligent and Connected Transportation Systems (ICTS) have become a practical and valuable alternative for wide variety of novel applications in road traffic safety. It can be utilized to guarantee road safety and create new forms of inter-vehicle communications. However, due to the high speed of vehicles, the topology of the network is highly dynamic and the network may be disconnected frequently, which will lead to a decline in communication performance. Delay Tolerant Networks (DTNs) follow the approach to store and forward the message. DTNs can adapt to the highly dynamic scenario, envisioned for communication in ICTS suffering from intermittent connection. In this paper, we propose the Social Probability And Resource Effective (SPARE) protocol to improve delivery ratio and minimize the consumption of network resources. In SPARE, we focus on considering four factors that include the nodal resources effective consumption, encounter probability, nodal historical encounter information and the number of messages carried by nodes. We use the nodes’ resources efficiency and encounter probability similarity to improve the delivery ratio of SPARE algorithm. In addition, SPARE applies the mechanism of dynamically managing messages to reduce network overhead. Finally, the simulation results show that SPARE achieves a higher delivery ratio and lower overhead ratio, compared to other protocols within resource constrained network situations.

Intercommunity Detection Scheme for Social Internet of Things: Compressive Sensing Over Graphs Approach

As a cluster between Internet of Things (IoT) and mobile social networks (MSNs), social IoT allows close interaction between humans and things. Many applications of IoT and MSN are based on the community structure to realize efficient services, and thus the detection of the community structure has become a key problem and attracted much academic attention. In this paper, a compressive sensing (CS) over graphs-based intercommunity detection scheme is proposed for the social IoT. By exploiting the probability of two nodes encountering each other, the encounter probability and the edge-clustering coefficient are utilized to define a novel metric for each connection and construct the measurement matrix. Then a CS-based detection algorithm is proposed to detect the intercommunity links. Moreover, the edge-clustering coefficient is exploited as the prior information to further improve accuracy and reduce complexity. Simulations show that the proposed detection scheme outperforms the conventional random walk-based scheme in the social IoT.

They don’t live forever: How life history data and encounter probability help to assess success of Muscardinus avellanarius translocations (Rodentia: Gliridae)

Abstract The hazel dormouse (Muscardinus avellanarius) is a European Protected Species and for this reason, hazel dormice are protected from deliberate killing, injury or disturbance and its sites and resting places are also protected. During development projects impacts on hazel dormouse individuals and populations should be avoided. If avoidance is not possible measures of mitigation and compensation have to be implemented. In many cases the only suitable measure to prevent disturbance, killing or injury of individuals is the translocation of hazel dormice to another suitable habitat. The success of translocations has so far been rarely documented. To assess the success of translocations, the natural mortality of hazel dormice has to be considered as well as the likelihood of finding specific individuals during the proposed action. How these data affect the assessment of translocation success is calculated based on published data on seasonal survival rates of different cohorts and of unpublished monthly encounter probabilities of a population of marked animals. Depending on the time between the translocation event and the subsequent monitoring controls the number of hazel dormice likely to be alive can be low. For this reason, success cannot be evaluated with our method if the sample size is too small.

Olfactory cues and the value of information: voles interpret cues based on recent predator encounters

Prey strategically respond to the risk of predation by varying their behavior while balancing the tradeoffs of food and safety. We present here an experiment that tests the way the same indirect cues of predation risk are interpreted by bank voles, Myodes glareolus, as the game changes through exposure to a caged weasel. Using optimal patch use, we asked wild-caught voles to rank the risk they perceived. We measured their response to olfactory cues in the form of weasel bedding, a sham control in the form of rabbit bedding, and an odor-free control. We repeated the interviews in a chronological order to test the change in response, i.e., the changes in the value of the information. We found that the voles did not differentiate strongly between treatments pre-exposure to the weasel. During the exposure, vole foraging activity was reduced in all treatments, but proportionally increased in the vicinity to the rabbit odor. Post-exposure, the voles focused their foraging in the control, while the value of exposure to the predator explained the majority of variation in response. Our data also suggested a sex bias in interpretation of the cues. Given how the foragers changed their interpretation of the same cues based on external information, we suggest that applying predator olfactory cues as a simulation of predation risk needs further testing. For instance, what are the possible effective compounds and how they change “fear” response over time. The major conclusion is that however effective olfactory cues may be, the presence of live predators overwhelmingly affects the information voles gained from these cues.Significance statementIn ecology, “fear” is the strategic response to cues of risk an animal senses in its environment. The cues suggesting the existence of a predator in the vicinity are weighed by an individual against the probability of encounter with the predator and the perceived lethality of an encounter with the predator. The best documented such response is variation in foraging tenacity as measured by a giving-up density. In this paper, we show that an olfactory predator cue and the smell of an interspecific competitor result in different responses based on experience with a live-caged predator. This work provides a cautionary example of the risk in making assumptions regarding olfactory cues devoid of environmental context.