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This paper is concerned with the deduction of a mathematical model for the small longitudinal vibrations of a bar where one end is clamped and in the other end is glued a concentrated mass. The existence of global solutions of this model perturbed with a general nonlinear internal dissipation and with a general nonlinear boundary dissipation is derived. For a particular case, the exponential decay rate of the energy is obtained. [ABSTRACT FROM AUTHOR]

To promote undergraduate education reform, teaching professional development (TPD) efforts aim to encourage instructors to adopt evidence-based practices. However, many instructors do not attend TPD. There may be many reasons for this, including low intrinsic motivation to participate in TPD. Psychologists have dealt with motivational barriers in educational contexts using psychosocial interventions, brief activities that draw on a rich history of psychological research to subtly alter key, self-reinforcing psychological processes to yield long-term intrinsic motivation and behavioral changes. Psychosocial interventions, for example, have been used to alter students' noncognitive attitudes and beliefs, such as attributions and mindset, which positively influence students' motivation and academic performance. Here, we propose that insights from research on psychosocial interventions may be leveraged to design interventions that will increase instructors' motivation to participate in TPD, thus enhancing existing pedagogical reform efforts. We discuss psychological principles and "best practices" underlying effective psychosocial interventions that could guide the development of interventions to increase instructors' motivation to attend TPD. We encourage new interdisciplinary research collaborations to explore the potential of these interventions, which could be a new approach to mitigating at least one barrier to undergraduate education reform.

The 2019 Undergraduate Biology Education Research Gordon Research Conference (UBER GRC), titled "Achieving Widespread Improvement in Undergraduate Education," brought together a diverse group of researchers and practitioners working to identify, promote, and understand widespread adoption of evidence-based teaching, learning, and success strategies in undergraduate biology. Graduate students and postdocs had the additional opportunity to present and discuss research during a Gordon Research Seminar (GRS) that preceded the GRC. This report provides a broad overview of the UBER GRC and GRS and highlights major themes that cut across invited talks, poster presentations, and informal discussions. Such themes include the importance of working in teams at multiple levels to achieve instructional improvement, the potential to use big data and analytics to inform instructional change, the need to customize change initiatives, and the importance of psychosocial supports in improving undergraduate student well-being and academic success. The report also discusses the future of the UBER GRC as an established meeting and describes aspects of the conference that make it unique, both in terms of facilitating dissemination of research and providing a welcoming environment for conferees.

Plants are colonized by numerous microorganisms serving important symbiotic functions that are vital to plant growth and success. Understanding and harnessing these interactions will be useful in both managed and natural ecosystems faced with global change, but it is still unclear how variation in environmental conditions and soils influence the trajectory of these interactions. In this study, we examine how nitrogen addition alters plant-fungal interactions within two species of Populus - Populus deltoides and P. trichocarpa. In this experiment, we manipulated plant host, starting soil (native vs. away for each tree species), and nitrogen addition in a fully factorial replicated design. After ~10 weeks of growth, we destructively harvested the plants and characterized plant growth factors and the soil and root endosphere fungal communities using targeted amplicon sequencing of the ITS2 gene region. Overall, we found nitrogen addition altered plant growth factors, e.g., plant height, chlorophyll density, and plant N content. Interestingly, nitrogen addition resulted in a lower fungal alpha diversity in soils but not plant roots. Further, there was an interactive effect of tree species, soil origin, and nitrogen addition on soil fungal community composition. Starting soils collected from Oregon and West Virginia were dominated by the ectomycorrhizal fungi Inocybe (55.8% relative abundance), but interestingly when P. deltoides was grown in its native West Virginia soil, the roots selected for a high abundance of the arbuscular mycorrhizal fungi, Rhizophagus. These results highlight the importance of soil origin and plant species on establishing plant-fungal interactions.

Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (AMFs) to elevated N availability, often leading to shifts in communities of AMF. However, physiological trade-offs among AMF taxa in their response to N enrichment vs the ability to acquire other soil nutrients could have negative effects on plant and ecosystem productivity. It follows that information on the functional traits of AMF taxa can be used to generate predictions of their potential role in mediating ecosystem responses to N enrichment. Arbuscular mycorrhizal fungi taxa that produce extensive networks of external hyphae should forage for N and phosphorus (P) more effectively, but these services incur greater carbon (C) costs to the plant. If N enrichment ameliorates plant nutrient limitation, then plants may reduce C available for AMF, which in turn could eliminate AMF taxa with large extensive external hyphae from the soil community. As a result, the remaining AMF taxa may confer less P benefit to their host plants. Using a synthesis of data from the literature, we found that the ability of a taxon to persist in the face of increasing soil N availability was particularly high in isolates from the genus Glomus, but especially low among the Gigasporaceae. Across AMF genera, our data support the prediction that AMF with a tolerance for high soil N may confer a lower P benefit to their host plant. Relationships between high N tolerance and production of external hyphae were mixed. Synthesis. If the relationship between N tolerance and plant P benefit is widespread, then shifts in arbuscular mycorrhizal fungi communities associated with N deposition could have negative consequences for the ability of plants to acquire P and possibly other nutrients via a mycorrhizal pathway. Based on this relationship, we predict that arbuscular mycorrhizal fungi responses could constrain net primary productivity in P-limited ecosystems exposed to N enrichment. This prediction could be tested in future empirical and modelling studies.

Gustavo Pretelín-Castillo,1 Mayra Silva Miranda,2,3 Clara Espitia,2,3 Rosa María Chávez-Santos,1 Abel Suárez-Castro,4 Luis Chacón-García,4 Rodrigo Aguayo-Ortiz,5 Roberto Martinez1 1Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Cd. México, 04510, México; 2Catedrática CONACYT adscrita al Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Cd. México, 04510, México; 3Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Departamento de Inmunología, Ciudad Universitaria, Cd. México, 04510, México; 4Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B-1, Ciudad Universitaria, Morelia Michoacán, 58030, México; 5Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Cd. México, 04510, MéxicoCorrespondence: Roberto MartinezInstituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Cd. México, 04510, MéxicoTel +52 55 56224441Fax +52 55 56162217Email robmar@unam.mxBackground: Tuberculosis is an infectious disease caused by the bacillus Mycobacterium tuberculosis. Compounds including a sulfur-containing scaffold have been shown to be key scaffolds in various antituberculosis agents. Interestingly, the 3-hydroxy-3-phenyl-prop-2-enedithioic acids 11a-j have, to the best of our knowledge, not been previously described as antituberculosis agents.Purpose: In the present study, we investigated the role of substituents attached to the phenyl ring of a 3-hydroxy-3-phenyl-prop-2-enedithioic acid scaffold (compounds 11a–j) in inhibiting the growth of M. tuberculosis strain H37Rv.Methods: (Z)-3-hydroxy-3-(4-R-phenyl)-prop-2-enedithioic acids 11b–j, with R groups including various electron-donating or electron-withdrawing groups, were designed by structurally modifying the lead compound 11a. The syntheses of 11a–j involved each one-step procedure starting from the corresponding substituted acetophenone. Compounds 11a–j were tested against M. tuberculosis strain H37Rv to evaluate their bacterial growth inhibitory activities. ADMET profiles were predicted by employing three different methods. In addition, molecular docking studies were carried out, based on the molecular similarities of the synthesized compounds with ethionamide ( 5), on the active site of the M. tuberculosis H37Rv (3R)-hydroxyacyl-ACP (HadAB) dehydratase heterodimer.Results: The antituberculosis activities of compounds 11a–j could be explained in terms of the presence of electron-donating or electron-withdrawing substituents on the aromatic ring of the substituted 3-hydroxy-3-phenyl)-prop-2-enedithioic acid core. The activity and selectivity index (SI) value of (Z)-3-hydroxy-3-(4-nitrophenyl)-prop-2-enedithioic acid 11e suggested that this compound could be used for the design of novel antituberculosis agents. Most of the synthesized molecules showed an acceptable ADME profile and a low probability of being toxic. Docking studies of 11d and 11e showed them forming hydrogen bonds with the ACys61 residue of the HadAB enzyme.Conclusion: Our results suggested that the antituberculosis compound 11e could be used for the design of novel antituberculosis agents.Keywords: synthesis, 3-hydroxy-3-(4-R-phenyl)-prop-2-enedithioic acids, antituberculosis agents, docking, theoretical ADME