Analysis of the National Transonic Facility mishap

The nonlinear dynamic finite element code DYnamic Crash Analysis of STructures (DYCAST) was used to model an accident scenario that occurred at the National Transonic Facility (NTF) wind tunnel. A post mishap investigation revealed that a total of five upstream bulkhead fairing plates were missing, three in one location and two in another. These plates were drawn into the wind tunnel's composite fan blades causing extensive damage. A DYCAST model was developed to determine if one-half of a small thermal shield flange clamp, weighing approximately 2.7 lbs., could have spun off the NTF drive shaft and impacted the bulkhead fairing plates with sufficient energy to cause failure of the attachment bolts. The clamp was presumed to have spun off at a tangent from the NTF drive shaft at a velocity of 1624 in/sec (drive shaft rotating at 580 rpm). The DYCAST analytical model predicts that impact of the 2.7 lbs projectile failed all of the bolts in two of the fairing plates allowing them to escape from the bulkhead ring with a low velocity of a few in/sec

Frontier Medicine: From the Atlantic to the Pacific, 1492–1941

Review of: "Frontier Medicine: From the Atlantic to the Pacific 1492–1941," by David Dary

Frontier Medicine: From the Atlantic to the Pacific, 1492–1941

Review of: "Frontier Medicine: From the Atlantic to the Pacific 1492–1941," by David Dary

Countering Far-Right Anti-Government Extremism in the United States

The far-right anti-government extremist movement poses a significant threat in the United States. The January 6, 2021, attack on the US Capitol illustrates the capacity of this movement to plan and mount violent attacks against government targets and democratic institutions. In this article, we explore how the organisational and tactical characteristics of the far-right anti- government movement in the United States enable it to thrive despite the dangers it poses to the public. We argue that its deep-seated ideological roots, fluid organisational structure, and mix of violent and nonviolent tactics make the movement difficult for federal and state authorities to proscribe, prosecute, and ultimately eliminate. US policymakers need to develop an informed response that accounts for the fluid, decentralised, and public-facing nature of anti- government extremism, as well as the pervasive distrust of federal authority that it reflects. We suggest that this approach will likely differ from the modern counter-terrorism tools that were initially designed to combat terrorist threats emanating from abroad, such as those posed by Al Qaeda and the Islamic State. We ground our arguments in evidence from cases of anti-government extremist groups and followers active in the United States over the past three decades

Sheepish: Posthumanism and the ovine in contemporary art

Ovine imagery in contemporary art is represented by works as diverse in media as they are linked in meaning with art historical precedents. Practices embracing taxidermic sheep, documentary film footage, carcassbuilt sculpture, graphic novels, printmaking, drawing and works made through the action of sheep participate in a narrative in confluence with, or contradiction of, the contemporary view of the animal in posthumanist theory. The many contemporary iterations of sheep and lamb imagery are synchronous with the animal turn in art and posthumanist thought yet author a larger anthropomorphism that calls this relationship into question. The representation of ovine tropes is part of a millennia long history of anthropomorphic imagery embedded in our culture, addressing themes of Christology, soteriology, nation, and sacrifice that clearly position these works outside the rubric of animal art. Each of the artists whose practices participate in this discussion—Henry Moore, Damien Hirst, and Andy Goldsworthy—open a point of interrogation in a larger discussion framed by posthumanist theory, offering an enduringly humanist reading that belies contemporary discourse

Spatial and temporal dynamics of retinal ganglion cells with different photoreceptor inputs

The retina must operate over a wide range of light levels. Two classes of input cells, rods and cones, specialised to different light conditions evolved to achieve this task. This thesis examines how interactions between these two classes shape retinal output as the light level changes, and the extent to which loss of one class can alter processing of the remaining class. Retinal ganglion cell (RGC) receptive elds were characterised using multielectrode array recordings performed during presentation of spatiotemporal white noise across a 4.5 log10 light level range. Receptive fi eld properties were compared between wild-type mice, mice lacking functional cones (cpfl1 model of achromatopsia), and mice lacking functional rods (rd17 model of congenital stationary night blindness). The response of RGCs to otherwise identical stimuli changed with ambient light level. In low light conditions, wild-type RGCs had a longer latency to spike and were shifted towards higher temporal and lower spatial frequency tuning. Of those RGCs characterised at multiple light levels, 28% changed the polarity of their receptive fields between ON and OFF. These polarity switches occurred between every possible pair of light levels, and several cells were observed to switch multiple times. RGCs which switched polarity were identi ed in both rd17 and cpfl1 mice, indicating that at least some circuit mechanisms responsible are driven by a single photoreceptor cell class. Loss of function in one photoreceptor cell class altered visual processing of inputs from the remaining class. In low light conditions, RGCs in cpfl1 mice showed shorter latency to spike and a marked shift towards higher temporal frequency tuning, a receptive field property that is often understood as indicating tuning to visual motion. This difference in visual processing could result in behavioural differences, for instance these mice may exhibit better contrast sensitivity at temporal frequencies in low light conditions

Middle school teachers' perceptions of professional development experiences

The purpose of this study was to examine western North Carolina’s middle school teachers’ perceptions of the professional development experiences they participated in during the 2009-2010 school year and whether or not the professional development they participated in contributed to student achievement and positively affected classroom practice. There were 862 teachers from 21 public middle schools who received an invitation to participated in the study; 230 responded for a return rate of 27.6%. This study attempted to answer these questions: (1) To what extent do middle school teachers believe their professional development during the 2009-2010 school year was aligned with the Learning Forward Standards? (2) In what ways do middle school teachers believe their professional development during the 2009-2010 school year had a positive impact on their classroom practices and student achievement? (3) Is there a relationship between middle school teachers’ perceptions of the adherence to Learning Forward Standards and the teachers’ gender, the teachers’ years of experience, the subject(s) taught, and the size of the district? (4) Is there a relationship between middle school teachers’ perceptions of the impact of professional development on their classroom practices and student achievement and the teachers’ gender, the teachers’ years of experience, the subject(s) taught, and the size of the district? (5) What do middle school teachers perceive as their greatest professional development need? (6) What professional development experience do middle school teachers say is the most beneficial experience of their career? The conceptual framework based upon Learning Forward’s professional development standards provided the foundation for exploring how teachers perceived their professional development experiences. The researcher-designed survey was developed around the twelve elements of the professional development standards. Teachers’ perceptions of their professional development experiences were correlated with teachers’ gender, teachers’ years of experience, subject(s) taught, and the size of the district. The quantitative data analyzed included teachers’ gender, teachers’ years of experience, subject(s) taught, and the size of the district. Qualitative data included the teachers’ descriptions of their most beneficial professional development experience as well as those teachers believed impacted their classroom practices and student achievement. Teachers were asked to identify their greatest professional development need. After analysis of the survey data, a focus group, from the district where teacher perceptions closely aligned to the standards, was convened to gain insight into the teachers’ perceptions of their professional development experiences. This study found teachers believed their professional development was aligned or strongly aligned with the items on the survey representing the standards. Teachers indicated that learning about specific instructional programs and collaboration with other teachers had the greatest impact on their classroom practices. Similarly, teachers indicated that learning about specific instructional programs and collaboration with other teachers had the greatest impact on their student achievement. Nearly three-fourths of the teachers reported their greatest professional development need had a content-specific focus. Teachers reported their most beneficial professional development experience was content-specific