Delay-induced multistability near a global bifurcation

We study the effect of a time-delayed feedback within a generic model for a saddle-node bifurcation on a limit cycle. Without delay the only attractor below this global bifurcation is a stable node. Delay renders the phase space infinite-dimensional and creates multistability of periodic orbits and the fixed point. Homoclinic bifurcations, period-doubling and saddle-node bifurcations of limit cycles are found in accordance with Shilnikov's theorems.Comment: Int. J. Bif. Chaos (2007), in prin

Online forest biology and tree identification graduate class for public school educators

As a result of certification and accreditation standards, public school teachers are often required to take graduate education courses. However, it is often difficult for these teachers/students to take courses in residence at campuses. Further, there is often a shortage of specialized courses in their area of teaching. There is also a demand for natural-resource-based classes since, in Virginia, many of the standards of learning can be effectively taught using examples from forests. In response to the above issues, we developed an entirely online graduate course that covered forest biology, management, and tree identification. In the summer of 2001, 24 students successfully completed the course. Students were required to learn to identify 80 trees and shrubs in nine separate groups. They were also taught tree growth and structure, reproduction, carbon uptake, water relations, growth regulators, cold hardiness and dormancy, soils and site productivity, and silviculture. The course content was delivered on three CD-ROMS and administration occurred through a Web site. Nine cumulative tree ID quizzes were given online as well as two comprehensive exams covering the tree biology topics. We will present the basic structure of the course, class administration, share insights and student feedback

Instructors, Students, Managers, and the Basic Organizational Communication Course: Are We All Working Together or Working Apart?

Three studies were conducted to determine the extent of overlap between basic organizational communication textbook content (1990-2002), student perceptions of basic organizational communication knowledge and skills important for the workplace, and managerial expectations of communication knowledge and skills for graduates. Overall, findings indicate overlap on assigning importance to group/team communication, leadership, verbal communication, and conflict management; however, there were differences on a range of topics addressed in the basic organizational communication course deemed essential for job success. Implications of the studies’ findings indicate that organizational communication textbooks could emphasize more “soft skills” such as interpersonal relationships, listening, dealing with conflict, and so on, because of the premium today’s employers place on employees possessing those skills. Additionally, basic organizational communication instructors play a vital role in organizational communication education because they functions as a “translation specialist” for the students and employers

The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor

We investigated the nature of the magnetic phase transition in the Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization measurements performed in the magnetic field up to 90 kOe and temperature range 2-200 K showed that the magnetic ordering at temperatures below T = 50 K exhibits features characteristic for both spin-glass and ferromagnetic phases. The modified Sherrington - Southern model was applied to explain the observed transition temperatures. The calculations showed that the spin-glass state is preferred in the range of the experimental carrier concentrations and Mn content. The value of the Mn hole exchange integral was estimated to be J/pd/ = 0.45+/-0.05 eV. The experimental magnetization vs temperature curves were reproduced satisfactory using the non-interacting spin-wave theory with the exchange constant J/pd/ values consistent with those calculated using modified Sherrington - Southern model. The magnetization vs magnetic field curves showed nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of strong magnetic frustration in the system. The experimental results were reproduced theoretically with good accuracy using the molecular field approximation-based model of a disordered ferromagnet with long-range RKKY interaction.Comment: 9 pages, 6 figure

Diminished emotional empathic ability in Alexithymia

The present study has been designed to disentangle cognitive and emotional dimensions of empathy in a group of mentally healthy and highly alexithymic individuals (ALEX, n=24) and well-matched controls (n=26) with Interpersonal Reactivity Index (IRI) as questionnaire measure, and Multi Faceted Empathy Task (MET) used during the fMRI and after the fMRI. Simultaneously, Skin Conductance Response (SCR) has been acquired as an implicit measure of emotional reaction. Results show an impaired emotional empathic ability in alexithymic individuals, with lower levels of SCR and higher activation in prefrontal brain regions such as VLPFC and IFG. Cognitive empathy was not impaired in the alexithymic group and the results were accompanied by a higher activation left-IFG. The study leads to the conclusion that alexithymia doesn't only involve a diminished ability to identify and describe one’s own emotions. Furthermore, it is related to a deeper disability of emotion regulation, which becomes visible in impaired emotional concern for others and higher levels of personal distress

The Role of Mesotocin on Social Bonding in Pinyon Jays

The neuropeptide oxytocin influences mammalian social bonding by facilitating the building and maintenance of parental, sexual, and same‐sex social relationships. However, we do not know whether the function of the avian homologue mesotocin is evolutionarily conserved across birds. While it does influence avian prosocial behavior, mesotocin\u27s role in avian social bonding remains unclear. Here, we investigated whether mesotocin regulates the formation and maintenance of same‐sex social bonding in pinyon jays (Gymnorhinus cyanocephalus), a member of the crow family. We formed squads of four individually housed birds. In the first, “pair‐formation” phase of the experiment, we repeatedly placed pairs of birds from within the squad together in a cage for short periods of time. Prior to entering the cage, we intranasally administered one of three hormone solutions to both members of the pair: mesotocin, oxytocin antagonist, or saline. Pairs received repeated sessions with administration of the same hormone. In the second, “pair‐maintenance” phase of the experiment, all four members of the squad were placed together in a large cage, and no hormones were administered. For both phases, we measured the physical proximity between pairs as our proxy for social bonding. We found that, compared with saline, administering mesotocin or oxytocin antagonist did not result in different proximities in either the pair‐formation or pair‐maintenance phase of the experiment. Therefore, at the dosages and time frames used here, exogenously introduced mesotocin did not influence same‐sex social bond formation or maintenance. Like oxytocin in mammals, mesotocin regulates avian prosocial behavior; however, unlike oxytocin, we do not have evidence that mesotocin regulates social bonds in birds

Biodiversity comparison among phylogenetic diversity metrics and between three North American prairies

Protection of Earth’s ecosystems requires identification of geographical areas of greatest biodiversity. Assessment of biodiversity begins with knowledge of the evolutionary histories of species in a geographic area. Multiple phylogenetic diversity (PD) metrics have been developed to describe biodiversity beyond species counts, but sufficient empirical studies, particularly at fine phylogenetic scales, have not been conducted to provide conservation planners with evidence for incorporating PD metrics into selection of priority regions. We review notable studies that are contributing to a growing database of empirical results, we report on the effect of using high-throughput sequencing to estimate the phylogenies used to calculate PD metrics, and we discuss difficulties in selecting appropriate diversity indices. We focused on two of the most speciose angiosperm families in prairies—Asteraceae and Fabaceae—and compared 12 PD metrics and four traditional measures of biodiversity between three North American prairie sites. The varying results from the literature and from the current data reveal the wide range of applications of PD metrics and the necessity for many more empirical studies. The accumulation of results from further investigations will eventually lead to a scientific understanding upon which conservation planners can make informed decisions about where to apply limited preservation funds

Epigenetic Drifts during Long-Term Intestinal Organoid Culture

Organoids retain the morphological and molecular patterns of their tissue of origin, are self-organizing, relatively simple to handle and accessible to genetic engineering. Thus, they represent an optimal tool for studying the mechanisms of tissue maintenance and aging. Long-term expansion under standard growth conditions, however, is accompanied by changes in the growth pattern and kinetics. As a potential explanation of these alterations, epigenetic drifts in organoid culture have been suggested. Here, we studied histone tri-methylation at lysine 4 (H3K4me3) and 27 (H3K27me3) and transcriptome profiles of intestinal organoids derived from mismatch repair (MMR)-deficient and control mice and cultured for 3 and 20 weeks and compared them with data on their tissue of origin. We found that, besides the expected changes in short-term culture, the organoids showed profound changes in their epigenomes also during the long-term culture. The most prominent were epigenetic gene activation by H3K4me3 recruitment to previously unmodified genes and by H3K27me3 loss from originally bivalent genes. We showed that a long-term culture is linked to broad transcriptional changes that indicate an ongoing maturation and metabolic adaptation process. This process was disturbed in MMR-deficient mice, resulting in endoplasmic reticulum (ER) stress and Wnt activation. Our results can be explained in terms of a mathematical model assuming that epigenetic changes during a long-term culture involve DNA demethylation that ceases if the metabolic adaptation is disturbed