Phenological and altitudinal changes in plants responding to drying Neotropical Cloud Forests

Precipitation is a main abiotic cue for flowering and fruiting in tropical plants. Global warming is likely to alter abiotic cues in tropical montane cloud forests such as the Monteverde Cloud Forest in Costa Rica. The plants within the Monteverde Cloud Forest rely on cloud cover to provide precipitation through mist during the dry season. With rising sea surface temperatures caused by increased concentrations of atmospheric carbon dioxide, cloud bases are likely to move up in elevation. This has the potential to increase the number of days without mist during the dry season. It is also possible that plant species have changed their altitude ranges in response to warming. Here, I repeat a 1979-81 census of flowering and fruiting plants in the Monteverde Cloud Forest Reserve for a two-week period in mid-July. Sixty-four plant species were noted for flowering or fruiting, and sixteen showed evidence of phenological change. Eight plant species were also found that were previously reported only from lower elevations. Although a small number of plants had atypical patterns, the majority were flowering or fruiting on time. Still, phenology changes of even a few species could impact food webs. Novel communities are likely to form as plants move up in altitude in search of historical mist and seasonal conditions

Essays on Market Dynamics in the Presence of Learning

I investigate how the presence of learning affects the market dynamics in three different market settings. The first chapter studies how the interplay of individual and social learning affects price dynamics. I consider a monopolist selling a new experience good over time to many buyers. Buyers learn from their own private experiences (individual learning) as well as by observing other buyers\u27 experiences (social learning). Individual learning generates ex post heterogeneity, which affects the buyers\u27 purchasing decisions and the firm\u27s pricing strategy. When learning is through good news signals, the monopolist\u27s incentive to exploit the known buyers causes experimentation to be terminated too early. After the arrival of a good news signal, the price could instantaneously go down in order to induce the remaining unknown buyer to experiment. When learning is through bad news signals, experimentation is efficient, since only the homogeneous unknown buyers purchase the experience good. The second chapter is based on the observation that workers learn at different rates about their productivity and therefore expect different wage paths across firms. We show that under strict supermodularity there is always positive assortative matching: differential learning is always dominated by the impact of productivity. Surprisingly, this holds even if learning is faster in the low type firm. The key assumption driving this result is that this is a pure Bayesian learning model.We also derive a new equilibrium condition in this class of continuous time models in addition to the common smooth-pasting and value-matching conditions. This no-deviation condition captures sequential rationality and results in a restriction on the second derivative of the value function. The third chapter develops a continuous-time war of attrition model with learning to investigate whether learning is possible to make it easier to reach an agreement. I show that with exogenous private learning, it may be easier to reach an agreement initially but it becomes more and more difficult over time. The expected delay will always be higher than the expected delay without learning. I also show that when allowing only one player to learn leads to a shorter delay than allowing both to learn

Bilateral coordination of vocal pathways in African clawed frogs, Xenopus laevis

posterThis poster describes how bilateral coordination of motor programs are achieved in the central vocal pathways of African clawed frogs

Collective ethnic-racial identity and health outcomes among African American youth: Examination of promotive and protective effects

OBJECTIVES: Racial discrimination is associated with numerous negative health outcomes, including increased risk for depression and anxiety symptoms and substance use. Positive affect toward of one's ethnic or racial group (i.e., ethnic-racial identity affirmation) has been shown to buffer the negative effects of racial discrimination on health outcomes. The extent to which one believes his or her group is valued by others (i.e., positive collective ethnic-racial identity) has also been proposed to be protective. However, to date a limited body of research has examined the moderating effect of collective ethnic-racial identity on health, and among available studies, findings are mixed. METHOD: African American youth (N = 612; 58.2% female, M grade = 8) completed measures on experiences of discrimination, mood symptoms, substance use, ethnic-racial identity affirmation, and collective ethnic-racial identity (assessed using the Collective Self-Esteem Scale). RESULTS: Controlling for demographic variables and affirmation, a significant main effect was found for collective ethnic-racial identity, such that believing that others viewed your group positively was associated with better health outcomes among African American youth. However, collective ethnic-racial identity was not found to buffer the effects of discrimination on health outcomes. CONCLUSIONS: These findings highlight the importance of examining collective ethnic-racial identity and the promotive effect it can have on health outcomes for African Americans. More research is needed to better understand if there are health outcomes in which collective ethnic-racial identity may also mitigate risk as a consequence of racial discrimination. (PsycINFO Database Record (c) 2019 APA, all rights reserved)

MOST Space Telescope Photometry of the 2010 January Transit of Extrasolar Planet HD80606b

We present observations of the full January 2010 transit of HD80606b from the Canadian microsatellite, Microvariability and Oscillations of Stars (MOST). By employing a space-based telescope, we monitor the entire transit thus limiting systematic errors that result from ground observations. We determine measurements for the planetary radius (R_{p}=0.987\pm0.061R_{Jup}) and inclination (i=89.283^{o}\pm0.024) by constraining our fits with the observed parameters of different groups. Our measured mid-transit time of 2455210.6449\pm0.0034 HJD is consistant with the 2010 Spitzer results and is 20 minutes earlier than predicted by groups who observed the June 2009 transit.Comment: 3 figure

Distinct neural control of vocal phases in frog calls

posterThis poster describes how the connections within the central vocal pathways of African clawed frogs are responsible for coordinating distinct part of their calls

Rhythm generation, coordination, and initiation in the vocal pathways of male African clawed frogs

Poste

Challenges of Integrating NASAs Space Communication Networks

The transition to new technology, innovative ideas, and resistance to change is something that every industry experiences. Recent examples of this shift are changing to using robots in the assembly line construction of automobiles or the increasing use of robotics for medical procedures. Most often this is done with cost-reduction in mind, though ease of use for the customer is also a driver. All industries experience the push to increase efficiency of their systems; National Aeronautics and Space Administration (NASA) and the commercial space industry are no different. NASA space communication services are provided by three separately designed, developed, maintained, and operated communications networks known as the Deep Space Network (DSN), Near Earth Network (NEN) and Space Network (SN). The Space Communications and Navigation (SCaN) Program is pursuing integration of these networks and has performed a variety of architecture trade studies to determine what integration options would be the most effective in achieving a unified user mission support organization, and increase the use of common operational equipment and processes. The integration of multiple, legacy organizations and existing systems has challenges ranging from technical to cultural. The existing networks are the progeny of the very first communication and tracking capabilities implemented by NASA and the Jet Propulsion Laboratory (JPL) more than 50 years ago and have been customized to the needs of their respective user mission base. The technical challenges to integrating the networks are many, though not impossible to overcome. The three distinct networks provide the same types of services, with customizable data rates, bandwidth, frequencies, and so forth. The differences across the networks have occurred in effort to satisfy their user missions' needs. Each new requirement has made the networks more unique and harder to integrate. The cultural challenges, however, have proven to be a significant obstacle for integration. Over the past few decades of use, user missions and network personnel alike have grown accustomed to the processes by which services are provided by the NASA communications and navigation networks. The culture established by each network has created several challenges that need to be overcome in order to effectively integrate the networks. As with any change, there has been resistance, an apprehension to explore automation of existing processes, and a working environment that attempts to indirectly influence change without mandating compliance. Overcoming technical and cultural challenges is essential to successfully integrating the networks and although the challenges are numerous, the integration of the networks promises a more efficient space communications network for NASA and its customers, as well as potential long-term cost savings to the agency. This paper, Challenges of Integrating NASA Legacy Communications Networks, will provide a brief overview of the current NASA space communications networks as well as the an overview of the process implemented while performing the SCaN Trade Studies and an introduction to the requirements driving integration of the SCaN Networks. This paper will describe in detail the challenges experienced, both technical and cultural, while working with NASA space communications network-specific personnel. The paper will also cover lessons learned during the performance of architecture trade studies and provide recommendations for ways to improve the process