395 research outputs found
Emerging structures in social networks guided by opinions' exchanges
No full textIn this paper we show that the small world and weak ties phenomena can spontaneously emerge in a social network of interacting agents. This dynamics is simulated in the framework of a simplified model of opinion diffusion in an evolving social network where agents are made to interact, possibly update their beliefs and modify the social relationships according to the opinion exchange
Turing-like instabilities from a limit cycle.
No full textThe Turing instability is a paradigmatic route to pattern formation in reaction-diffusion systems. Following a diffusion-driven instability, homogeneous fixed points can become unstable when subject to external perturbation. As a consequence, the system evolves towards a stationary, nonhomogeneous attractor. Stable patterns can be also obtained via oscillation quenching of an initially synchronous state of diffusively coupled oscillators. In the literature this is known as the oscillation death phenomenon. Here, we show that oscillation death is nothing but a Turing instability for the first return map of the system in its synchronous periodic state. In particular, we obtain a set of approximated closed conditions for identifying the domain in the parameter space that yields the instability. This is a natural generalization of the original Turing relations, to the case where the homogeneous solution of the examined system is a periodic function of time. The obtained framework applies to systems embedded in continuum space, as well as those defined on a networklike support. The predictive ability of the theory is tested numerically, using different reaction schemes
Update on Donkey Embryo Transfer and Cryopreservation
No full textDonkey species reproductive biotechnology studies had a dramatic increase after the Convention of Biological Diversity that took place in Rio de Janeiro (Brazil) in 1992. The mechanization of agriculture of the 20th century took most of the developed countries donkey breeds close to extinction, and after Rio, the development of effective reproductive programs to save them was encouraged. Moreover, the recent interest in donkey milk, meat, and skin products transformed the donkey in a potential productive animal leading to the research and dissemination of desired productive tracts into its population. Among reproductive biotechnologies, the production and cryopreservation of embryos has a key role due to the possibility of producing and stocking valuable genetics potentially forever. Each species gametes and embryos from each species need specific media and protocols due to their particular characteristics. After more than 10 years of unsatisfactory results, embryo transfer and cryopreservation in the donkey moved from horse protocols to procedures more specifically tailored to the donkey species. Nowaday, pregnancy rates of 50% and 36% after the transfer of fresh and vitrified embryos, respectively, are possible in this species
Generalized patterns from local and non local reactions
No full textA class of systems is considered, where immobile species associated to distinct patches, the nodes of a network, interact both locally and at a long-range, as specified by an (interaction) adjacency matrix. Non local interactions are treated in a mean-field setting which enables the system to reach a homogeneous consensus state, either constant or time dependent. We provide analytical evidence that such homogeneous solution can turn unstable under externally imposed disturbances, following a symmetry breaking mechanism which anticipates the subsequent outbreak of the patterns. The onset of the instability can be traced back, via a linear stability analysis, to a dispersion relation that is shaped by the spectrum of an unconventional reactive Laplacian. The proposed mechanism prescinds from the classical Local Activation and Lateral Inhibition scheme, which sits at the core of the Turing recipe for diffusion driven instabilities. Examples of systems displaying a fixed-point or a limit cycle, in their uncoupled versions, are discussed. Taken together, our results pave the way for alternative mechanisms of pattern formation, opening new possibilities for modeling ecological, chemical and physical interacting systems
Variables Affecting Veterinary Students’ Ability to Accurately Interpret Ovulation in Live Mare Palpation
No full textn a veterinary medicine curriculum, students' hands-on practice is essential but is still considered one of the major deficiencies in veterinary schools in Europe. After theoretical and basic practical training, students, under the control of experienced veterinarians (supervisors), monitored the reproductive cycle of embryo recipients by transrectal palpation and ultrasound. To evaluate the skills of students, the question "Has she ovulated?" was posed when a dominant follicle ≥ 35 mm was recorded in the previous day's examination and a score of 1 or 0 was assigned in the case of a correct or incorrect answer (test palpation), respectively. Study 1 involved the retrospective evaluation of 3,509 test palpation records of 43 students (31 females, 12 males) and showed a statistically significant positive correlation between the number of test palpations performed and the proportion of correct answers. There was a statistically significant effect of the number of test palpations performed by each student, their gender, and the season on the correct answers. When performing > 50 test palpations, a statistical difference between gender was observed (p < .05). Study 2 involved the prospective evaluation of 687 records on 52 standardbred or thoroughbred recipient mares collected from nine right-handed female students. The different mares, breed, occurrence of ovulation on the left or right ovary, and the presence of one or more large follicle(s) per ovary had no effect on the correct answers (p > .05). Individual students' performances were statistically different (p < .05), ranging from 60% to 92%
Ultrasonographic Pregnancy Diagnosis in the Mare
No full textPregnancy diagnosis is crucial in managing horse reproduction, influencing breeding strategies, mare health monitoring, and herd productivity. Accurate diagnosis ensures effective resource allocation and appropriate care for pregnant mares. Ultrasonography, a noninvasive imaging technique, uses sound waves to create body images. In equine reproductive management, it visualizes the conceptus and detects abnormalities during the embryonic and fetal stages. One key advantage is early pregnancy detection, enabling timely care and management. Ultrasonography also assesses embryo viability and monitors fetal development, identifying potential issues for prompt intervention. While ultrasonography is a powerful tool, its effectiveness depends on the operator’s skill and the mare’s condition. Practitioners must tailor their diagnostic approach to individual cases. Despite its strengths, understanding its limitations is crucial. By enabling early pregnancy detection, regular monitoring, and identifying potential issues, ultrasonography significantly contributes to reproductive success. It ensures the health and welfare of the mare and her offspring, ultimately enhancing overall equine well-being. In conclusion, ultrasonography is vital in equine reproductive management, playing a key role in pregnancy diagnosis, monitoring, and promoting equine welfare. Effective use of this tool can greatly enhance the success of equine reproduction efforts
Recipients’ pregnancy rate was affected by season but not by the temperature humidity index (THI) in an equine commercial ET program in Southern Europe
No full textThis study retrospectively analysed the effects of different environmental factors such as the photoperiod, temperature/humidity index of 19 years of a commercial embryo transfer programme performed in central Italy. From 340 donors of different breeds and aged between 2 and 25 years, 576 embryos of an excellent or good quality were obtained by uterine flushing on days 7–8 after ovulation. The embryos were transferred to 259 recipients, aged between 2 and 16 years, and belonging to different breeds. Both the donors and the recipients were employed for several cycles/years. At the time of transfer, the recipients were in diestrus, from day 4 to day 8 after ovulation, and were classified as excellent or good based on clinical examination findings. Out of the total number of embryos transferred, 437 pregnancies were obtained at 14 days (75.9%), with 48/437 (10.1%) embryonic losses at 40 days; with no significant differences among years. Significant differences (p < .05) were observed between 14‐day pregnancy rates for transfers performed during the spring transition and breeding seasons (77.1%) compared to those performed during the autumn transitional season (57.9%). No effect of temperature/humidity index was found on pregnancy rates or pregnancy losses after the transfer to the recipients (p > .05). Embryo transfer during autumn was less successful than the transfers performed during the spring transition and the breeding season
Random walks on hypergraphs
No full textIn the past 20 years network science has proven its strength in modeling many real-world interacting systems as generic agents, the nodes, connected by pairwise edges. Nevertheless, in many relevant cases, interactions are not pairwise but involve larger sets of nodes at a time. These systems are thus better described in the framework of hypergraphs, whose hyperedges effectively account for multibody interactions. Here we propose and study a class of random walks defined on such higher-order structures and grounded on a microscopic physical model where multibody proximity is associated with highly probable exchanges among agents belonging to the same hyperedge. We provide an analytical characterization of the process, deriving a general solution for the stationary distribution of the walkers. The dynamics is ultimately driven by a generalized random-walk Laplace operator that reduces to the standard random-walk Laplacian when all the hyperedges have size 2 and are thus meant to describe pairwise couplings. We illustrate our results on synthetic models for which we have full control of the high-order structures and on real-world networks where higher-order interactions are at play. As the first application of the method, we compare the behavior of random walkers on hypergraphs to that of traditional random walkers on the corresponding projected networks, drawing interesting conclusions on node rankings in collaboration networks. As the second application, we show how information derived from the random walk on hypergraphs can be successfully used for classification tasks involving objects with several features, each one represented by a hyperedge. Taken together, our work contributes to unraveling the effect of higher-order interactions on diffusive processes in higher-order networks, shedding light on mechanisms at the heart of biased information spreading in complex networked systems
The Current Situation and Trend of Donkey Industry in Europe
No full textOwing to the mechanization in agriculture and transport, the number of donkeys reared in Europe was reduced of 50% in the last 20 years and more than 80% since the middle of the last century. During this period, no attention was devoted to the breeding selection and biodiversity conservation, with the results that, nowadays, most of the European breeds of donkey are threatened of extinction. The remaining donkeys, in Europe, are employed for niche purposes as mule production or maintenance of soil and landscape. The consumption of donkey meat is not popular in Europe, and a few animals are sent to the slaughterhouse. A new interest is growing in Europe for donkey milk, mostly for human consumption, but also for the production of beauty products. Marginal areas of donkey employment are the social and leisure uses. In spite of the fact that interest for donkey in Europe is very marginal and very few or even no funding for research were provided from national or European authorities, more or less one third of articles published on different aspect of donkey sciences in the last 20 years were produced in Europe
Pattern formation for reactive species undergoing anisotropic diffusion
No full textTuring instabilities for a two species reaction-diffusion systems is studied under anisotropic diffusion. More specifically, the diffusion constants which characterize the ability of the species to relocate in space are direction sensitive. Under this working hypothesis, the conditions for the onset of the instability are mathematically derived and numerically validated. Patterns which closely resemble those obtained in the classical context of isotropic diffusion, develop when the usual Turing condition is violated, along one of the two accessible directions of migration. Remarkably, theinstability can also set in when the activator diffuses faster than the inhibitor, along the direction for which the usual Turing conditions are not matche
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