International Journal of Recirculating Aquaculture

Production characteristics of palmetto bass (Morone saxatilis female x Morone chrysops male) reared at three stocking densities (36 fish/m3, 72 fish/m3, and 144 fish/m3) in a pilot-scale RAS were evaluated. A final mean ±SE fish weight of 412.1 ± 7.8 g at the high density was significantly lower than that of fish at the medium density weighing 542.1 ± 11 .8 g (P < 0.05). Fish weight (676.1 ± 17 .0 g) at_ the lowest density was significantly higher than at the high and medium densities (P < 0.05). The average daily weight gain at the low density (2.8 g/d) was 22% and 47% higher than fish reared at the medium and high densities, respectively. Total biomass gains of 733.8, 483.3, and 297.9 kg were obtafued at the high, medium, and low densities. Feed conversion and survival rates were similar among densities averaging 1.4 and 97 .1 %, respectively. Higher mean daily and cumulative feed totals at the highest density contributed to significantly higher ammonia and nitrite concentrations and lower pH levels at haryest. All other measured water quality parameters were similar among densities and remained within known acceptable limits for fish growth. The results indicated that palmetto bass reared in closed systems reached market size in 224 days at the low and medium densities. However, the relative biomass production may not justify such strategies when compared to the yield obtained at the highest rearing density

International Journal of Recirculating Aquaculture

Striped bass female (M. saxatilis) x white bass male (M. mississippiensis), (SBxWB, n = 300) and striped bass female x yellow bass male (M. chrysops) (SBxYB, n = 300) fingerlings, initial mean weight 91 g and 62 g, respectively, were reared in recirculating aquaculture systems at densities of 118 fish/m3 for 120 days. Mean weight increased 309 g and 151 gin SBxWB and SBxYB, respectively. ,final mean weight and total length, and rate of weight and length increase were higher for SBxWB than SBxYB. Condition factor and survival were higher for SBxYB (1.04 and 99.3%, respectively) than for SBxWB (1.01 and 96.0%,respectively). Mean feed conversion ratio (FCR) was lower for SBxWB (1.4) than for SBxYB (1.6). Significant time x hybrid interactions indicated that growth rate of SBxYB improved, relative to SBxWB, as the study progressed. Positive linear trends for total ammonia, unionized ammonia, and nitrite indicate water quality deteriorated as the study progressed. Time x hybrid interactions for growth rate may have been due to differential responses of SBxYB and SBxWB to deterioration of water quality. Although SBxYB had slightly better survival than SBxWB and their growth rate improved relative to that of SBxWB, the slow overall growth of SBxYB limits its potential for recirculating system production

Variations on a Theme: The Shift From Distinction to Commonality in Philadelphia's Diverse Provider Model 2002–2008

Recent years have seen a growing push toward Portfolio Management Models that incorporate a variety of providers operating public schools. One rationale for this is that such organizations can offer distinct and innovative educational practices. This article describes the Diverse Provider Model implemented in Philadelphia from 2002-2008, and the shifts in practices by many outside providers away from distinction and toward alignment with the district approach. Drawing on institutional theory, we examine possible explanations for these shifts, including the particular structures and incentives in Philadelphia and discuss what can be learned about the prospects for innovation through outside providers

A freely-moving monkey treadmill model

Objective: Motor neuroscience and brain-machine interface (BMI) design is based on examining how the brain controls voluntary movement, typically by recording neural activity and behavior from animal models. Recording technologies used with these animal models have traditionally limited the range of behaviors that can be studied, and thus the generality of science and engineering research. We aim to design a freely-moving animal model using neural and behavioral recording technologies that do not constrain movement. Approach: We have established a freely-moving rhesus monkey model employing technology that transmits neural activity from an intracortical array using a head-mounted device and records behavior through computer vision using markerless motion capture. We demonstrate the excitability and utility of this new monkey model, including the first recordings from motor cortex while rhesus monkeys walk quadrupedally on a treadmill. Main results: Using this monkey model, we show that multi-unit threshold-crossing neural activity encodes the phase of walking and that the average ring rate of the threshold crossings covaries with the speed of individual steps. On a population level, we find that neural state-space trajectories of walking at different speeds have similar rotational dynamics in some dimensions that evolve at the step rate of walking, yet robustly separate by speed in other state-space dimensions. Significance: Freely-moving animal models may allow neuroscientists to examine a wider range of behaviors and can provide a flexible experimental paradigm for examining the neural mechanisms that underlie movement generation across behaviors and environments. For BMIs, freely-moving animal models have the potential to aid prosthetic design by examining how neural encoding changes with posture, environment, and other real-world context changes. Understanding this new realm of behavior in more naturalistic settings is essential for overall progress of basic motor neuroscience and for the successful translation of BMIs to people with paralysis

The Changing Nature of Private Engagement in Public Education: For-Profit and Nonprofit Organizations and Educational Reform

Recent years have seen a shifting landscape around private engagement in K-12 public education, one that involves a reorientation of education policy and practice around the principles of the marketplace. In this article, we examine the roles of both not-for-profit and for-profit agencies, as distinct from government agencies, in this movement. Past research has generally focused on subsets of these private actors (i.e., for-profit firms, charter management organizations, or alternative preparers of educators for public schools). We try to look more broadly in order to examine how private actors and the roles of those players in K-12 education are changing, both in terms of the scope of their engagement and the extent to which their role increasingly involves areas at the core of educational practice. In doing so, we consider some of the reasons for these changes, including the influence of federal policy, markets as drivers, and the broader political context.We conclude by raising questions for future research and examining how these developments intersect with values such as democratic voice, equitable distribution of resources, and the public purposes of schooling