Operations of the Federal Reserve Bank of St. Louis - 1977

Federal Reserve Bank of St. Louis

Characterisation of host growth after infection with a broad-range freshwater cyanopodophage

Freshwater cyanophages are poorly characterised in comparison to their marine counterparts, however, the level of genetic diversity that exists in freshwater cyanophage communities is likely to exceed that found in marine environments, due to the habitat heterogeneity within freshwater systems. Many cyanophages are specialists, infecting a single host species or strain; however, some are less fastidious and infect a number of different host genotypes within the same species or even hosts from different genera. Few instances of host growth characterisation after infection by broad host-range phages have been described. Here we provide an initial characterisation of interactions between a cyanophage isolated from a freshwater fishing lake in the south of England and its hosts. Designated ΦMHI42, the phage is able to infect isolates from two genera of freshwater cyanobacteria, Planktothrix and Microcystis. Transmission Electron Microscopy and Atomic Force Microscopy indicate that ΦMHI42 is a member of the Podoviridae, albeit with a larger than expected capsid. The kinetics of host growth after infection with ΦMHI42 differed across host genera, species and strains in a way that was not related to the growth rate of the uninfected host. To our knowledge, this is the first characterisation of the growth of cyanobacteria in the presence of a broad host-range freshwater cyanophage

Feature Topography and Sound Intensity Level Encoding in Primary Auditory Cortex

The primary auditory cortex: A1) in mammals is one of the first areas in the neocortex that receives auditory related spiking activity from the thalamus. Because the neocortex is implicated in regulating high-level brain phenomena, such as attention and perception, it is therefore important in regards to these high-level behaviors to understand how sounds are represented and transformed by neuronal circuits in this area. The topographic organization of neuronal responses to auditory features in A1 provides evidence for potential mechanisms and functional roles of this neural circuitry. This dissertation presents results from models of topographic organization supporting the notion that if the topographic organization of frequency responses, termed tonotopy or cochleotopy, is aligned along the longest anatomical line segment in A1, as supported by some physiological studies, then it is unlikely that any other topography is mapped monotonically along the orthogonal axis. Thresholds of neuronal responses to sound intensity level represent a particular feature that may have a local, highly periodic topography and that is vital to the sensitivity of the auditory system. The neuronal representation of sound level in A1, particularly as it relates to encoding accuracy, contains a distribution of neurons with varying amounts of inhibition at high sound levels. Neurons with large amounts of this high-level inhibition are described as nonmonotonic or level-tuned. This dissertation presents evidence from single neuron recordings in A1 that neurons exhibiting greater high-level inhibition also exhibit lower neuronal thresholds and that lower thresholds in these nonmonotonic neurons are preserved even when much of the neuronal population is adapted for accurately encoding more intense sounds. Evidence presented in this dissertation also suggests that nonmonotonic neurons have transient responses to time-varying: dynamic) level stimuli that adapt more quickly in response to low-level sounds than those of monotonic neurons. Together these results imply that under static, steady-state-dynamic and transient-dynamic sound level conditions, nonmonotonic neurons are specialized encoders of less intense sounds that allow the auditory system to maintain sensitivity under a variety of environmental conditions

Mediating Teachers as Learners: Conversations from Shared Experience

Race to the Top mandates, much like other comprehensive reforms before, focuses on teacher quality and student outcomes. Measuring teacher quality, under Race to the Top reforms, remains a subject of uncertainty, particularly measuring for improvement. This article argues that a central purpose of classroom evaluation is to provide supportive, targeted feedback by differentiating teachers as learners. Drago-Severson and Mezirow offer a framework for adult learning that overlays this theoretical analysis. The three cases explored for this article demonstrate levels of adult learning among teachers, directing the novice to addressing the fully formed transformational learner. The cases promote professional learning as both social and reflective

A Study of the Effectiveness of Learning Communities at a Small Liberal Arts College

The purpose of this study is to determine the effectiveness of the learning community program at a small liberal arts college on educational outcomes as measured by differences in semester GPA between learning community participants and non-participants, as well as differences between types of learning communities, time of participation in learning communities, and the effect of demographic variables and prior attainment (converted SAT scores). Data was provided by a small liberal arts college on 294 participants. The sample was composed of 152 students who participated in a learning community and 142 who did not participate in a learning community for a total sample of 294 subjects. To address the four research questions posed in this study, the Statistical Package for the Social Sciences (SPSS) was used to conduct hierarchical multiple regressions as well as an ANCOVA. The dependent variables considered were first semester GPA, second-semester GPA, and converted SAT score for research question 1. The independent variables considered were learning community, gender, ethnicity, and converted SAT score. The results of the study indicate no effectiveness of participation in learning communities on improving student academic performance. None of the analyses showed any type of positive influence of the learning communities at the small liberal arts college on GPA. In addition, the hierarchical multiple regressions on Fall GPA and Spring GPA both showed that participation in a learning community indicated lower GPA. This result was more pronounced in the fall than in the spring

A Measurement Approach to Cognitive Complexity and Perception of Information: Implications for information Systems Design

Business decision makers were asked to evaluate and use various information reports, as might be supplied by an information system, in several decision making scenarios. Multi-dimensional scaling was utilized to detect underlying perceptual dimensions of the information (differentiation ability), and to assess the importance or salience placed on each of these various dimensions (discriminant ability). Preference mapping was utilized to assess the underlying decision rules used by the decision makers in using the various information items in decision making tasks. As expected, individual differences were found with respect to differentiation, discrimination, and integration abilities. However, further analysis demonstrated that relatively homogeneous groupings of decision makers could be formed which utilized information in decision making in a similar manner. The implications of the study indicate that information systems designers need to consider the cognitive characteristics of decision makers, and that information reports may be \u27 tailored to relatively cognitively homogeneous groups of design makers who perceive information in the same manner

Breadboard RL10-2B low-thrust operating mode (second iteration) test report

Cryogenic rocket engines requiring a cooling process to thermally condition the engine to operating temperature can be made more efficient if cooling propellants can be burned. Tank head idle and pumped idle modes can be used to burn propellants employed for cooling, thereby providing useful thrust. Such idle modes required the use of a heat exchanger to vaporize oxygen prior to injection into the combustion chamber. During December 1988, Pratt and Whitney conducted a series of engine hot firing demonstrating the operation of two new, previously untested oxidizer heat exchanger designs. The program was a second iteration of previous low thrust testing conducted in 1984, during which a first-generation heat exchanger design was used. Although operation was demonstrated at tank head idle and pumped idle, the engine experienced instability when propellants could not be supplied to the heat exchanger at design conditions