Labour's ‘strange blindness’ and the end of Jubilee

ABSTRACT

This essay responds to David Roediger's Seizing Freedom: Slave Emancipation and Liberty for All. After a brief examination of the central themes of the book, I turn to the author's emphasis upon political agency. I argue that this emphasis is necessary, given the political and scholarly aims of the book. At the same time, I suggest that the agency depicted in Seizing Freedom was simultaneously constrained by the cultural, political, and social forces discussed in Roediger's earlier companion volume, The Wages of Whiteness. I end the essay with a short discussion of the labour leader William Sylvis that attempts to synthesize insights from Seizing Freedom and The Wages of Whiteness in order to explain the ‘strange blindness’ that led white labour to systematically ignore and repress the activity of black workers.     

Computation of the role of kinetics,kinematics, posterior tibial slope and muscle cocontraction on the stability of ACL-deficient knee joint at heel strike – Towards identification of copers from non-copers

Rupture of anterior cruciate ligament (ACL) undermines normal activity and function of the knee joint and places it at higher risk of re-injury and degeneration. ACL reconstruction surgery neither necessarily ensures return to pre-injury activities nor alleviates risk of long-term degeneration. Here in this computational investigation of a lower-extremity hybrid model at heel strike (HS) of gait, we search for factors that influence the stability of the joint and hence the distinct performances between post-ACL injury copers and non-copers. Due to the very unstable state of the joint under the mean gait input data, joint rotations-moments, posterior tibial slope (PTS), and cocontraction were altered within the reported data in the literature and the effects on the joint stability (anterior tibial translation (ATT) and critical muscle stiffness coefficient (q_cr)) were investigated. Results indicate that, in presence of both a small extension moment (0.1 or 0.2 Nm/kg) and a flexion rotation (∼5–8°), ACL-deficient (ACL-D) knee joint stability substantially improves to levels computed in the pre-injury intact joint. In addition, low cocontraction levels of 1–3% (in hamstrings and quads only and not in gastrocnemii) and reduced PTS (by 5°) further improve ACL-D joint stability. Therefore for a stable joint with ATT < 3 mm and q_cr < 25 similar to those in the intact knee at HS, higher flexion angles (>5°) and a small extension moment (∼0.1–0.2 Nm/kg) (i.e., higher activity in hamstrings than quads) are required. A lower posterior tibial slope (by 5°) and a small minimum cocontraction level (1–3%) in hamstrings and quads (but not in gastrocnemii) are also beneficial. These results identify mechanisms likely in play at HS in gait of copers when compared to non-copers.     

Abundance of Diurnal Raptors in Relation to Prairie Dog Colonies: Implications for Bird-Aircraft Strike Hazard

Abstract: Some diurnal raptors are frequently observed at prairie dog (Cynomys sp.) colonies. As a result, some military installations have conducted prairie dog control activities to reduce the bird-aircraft strike hazard (BASH) potential of low-flying aircraft. To evaluate the validity of this management strategy, we assessed raptor associations with prairie dog colonies at 2 short-grass prairie study areas: southern Lubbock County, Texas, USA, and Melrose Bombing and Gunnery Range in east-central New Mexico, USA. We quantified diurnal raptors (i.e., Falconiformes) at plots occupied (colony plots) and unoccupied (noncolony plots) by black-tailed prairie dogs (Cynomys ludovicianus) at both sites throughout 2002. We compared the number of individual birds of a given species at colony and noncolony plots within each study area by season. Ferruginous hawks (Buteo regalis) and northern harriers (Circus cyaneus) were more abundant at colony plots, whereas Swainson's hawks (B. swainsoni) and American kestrels (Falco sparverius) were more abundant at noncolony plots. Red-tailed hawk (B. jamaicensis) abundance did not differ between the 2 plot types. Our results suggest prairie dog control as a method of reducing BASH potential may be effective at some sites but may be ineffective or even increase the BASH potential at others. Thus, bird-avoidance models assessing the BASH potential should be conducted on a site-specific basis using information on relative and seasonal abundances of individual raptor species and the relative strike risks they pose to aircraft.     

Bat Strikes in the Australian Aviation Industry

ABSTRACT Bat collisions are a threat to commercial and military aircraft in Australia. We examined bat strike records from Australia during 1996–2006 and found that risk of impact from bats is increasing, is greatest in tropical versus temperate regions, and is more likely during early evening and while an aircraft is landing rather than departing. Temporal patterns of bat strikes differ from those of birds, highlighting the need to employ taxon-specific management strategies to minimize animal impacts on the aviation industry. The use of genetics for identification of strike remains and the implementation of nocturnal survey techniques by wildlife managers at airports will contribute to the mitigation of bat strikes.     

Blowfly succession from possum (Trichosurus vulpecula) carrion in a sheep-farming zone

The significance of brushtail possum, Trichosurus vulpecula Kerr (Diprotodontia: Phalangeridae) carcasses to the succession and production of Diptera species and its relevance to fly strike management in Tasmania, Australia was examined. Calliphora stygia (Fabricius), Lucilia sericata (Meigen) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) were found to be the most abundant and Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) always the least abundant (< 1%) of the putative primary fly invading species to emerge. Carcasses that were left for up to 15 days in the field before being exposed to flies for 2 days also acted as breeding sites for large numbers of all primary fly species, with the exception of L. cuprina. Ordination analysis revealed no relationship between possum carcasses according to their length of exposure but did show significant negative associations between the number of putative secondary invaders (Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae), Chrysomya varipes (Macquart) (Diptera: Calliphoridae) and putative tertiary flies (Hydrotaea rostrata Robineau-Desvoidy (Diptera: Muscidae)) to the number of C. vicina or C. stygia to emerge. There was enormous variability in the numbers of secondary/tertiary fly species to emerge from carcasses (0-11 450) that negatively correlated with the proportion of all flies to emerge that were primary, and with the mean size of adult L. sericata. Although carcass temperatures, especially those with a large larval population, were elevated, this did not appear to result in significant pre-adult fly mortality. The most important primary fly strike species L. cuprina was only found in insignificant numbers, whereas three other members of the fly strike fauna C. stygia, L. sericata and Ch. rufifacies did use possum carrion as an important breeding resource, but left implications for fly strike management inconclusive.     

机场鸟击防治的景观生态学途径

鸟击事件是全球范围的航空难题。随着我国生态环境的改善和航班量的增多,近年来鸟击事件逐年增加。科学快速的识别机场周围高危鸟类防治的关键区域,合理使用景观生态学途径来布局与规划鸟击防治手段是机场鸟击研究的空白点。对华北地区某机场的鸟情和生态环境开展调研,得到该机场及其周边地区的3种高危鸟类分布规律。通过构建高危鸟类的生态安全格局,并结合分区域防治的思路,最终得到该机场高危鸟类防治生态安全格局。从而识别出需要驱赶、防范与引诱的斑块、廊道与战略点,进而采取排斥力与吸引力结合的双向驱鸟策略。研究结果表明：（1）该机场8 km范围内鹭科类分布较多,廊道密集;雁鸭类与鸥科类栖息地较少但仍有廊道穿场。应对该范围内林地、水域等环境进行整修与清理,减少鹭科类的栖息地,切断高危鸟类飞行廊道。（2）该机场8-15 km范围内应重点做好雁鸭类的防护,及时切断雁鸭类向8 km范围内飞行的廊道。加强保护和改造连接15 km范围外的鸟类飞行廊道。（3）该机场15-20 km范围内应增加鸟类吸引力,打造连续的保护战略点,从而形成环状飞行廊道,将高危鸟类控制在安全范围内。     

Foot joint coupling variability differences between habitual rearfoot and forefoot runners prior to and following an exhaustive run

As joint coupling variability has been associated with running-related lower extremity injury, the purpose of this study was to identify how variability within the foot may be different between forefoot (FFS) and rearfoot strike (RFS) runners. Identifying typical variability in uninjured runners may contribute to understanding of ideal coordination associated with running foot strike patterns.Fifteen FFS and 15 RFS runners performed a maximal-effort 5 km treadmill run. A 7-segment foot model identified 6 functional articulations (rearfoot, medial and lateral midfoot and forefoot, and 1st metatarsophalangeal) for analysis. Beginning and end of the run motion capture data were analyzed. Vector coding was used to calculate 6 joint couples. Standard deviations of the coupling angles were used to identify variability within subphases of stance (loading, mid-stance, terminal, and pre-swing). Mixed between-within subjects ANOVAs compared differences between the foot strikes, pre and post run.Increased variability was identified within medial foot coupling for FFS and within lateral foot coupling for RFS during loading and mid-stance. The exhaustive run increased variability during mid-stance for both groups.Interpretation. Joint coupling variability profiles for FFS and RFS runners suggest different foot regions have varying coordination needs which should be considered when comparing the strike patterns.     

Joint contact loading in forefoot and rearfoot strike patterns during running

Research concerning forefoot strike pattern (FFS) versus rearfoot strike pattern (RFS) running has focused on the ground reaction force even though internal joint contact forces are a more direct measure of the loads responsible for injury. The main purpose of this study was to determine the internal loading of the joints for each strike pattern. A secondary purpose was to determine if converted FFS and RFS runners can adequately represent habitual runners with regards to the internal joint loading. Using inverse dynamics to calculate the net joint moments and reaction forces and optimization techniques to estimate muscle forces, we determined the axial compressive loading at the ankle, knee, and hip. Subjects consisted of 15 habitual FFS and 15 habitual RFS competitive runners. Each subject ran at a preferred running velocity with their habitual strike pattern and then converted to the opposite strike pattern. Plantar flexor muscle forces and net ankle joint moments were greater in the FFS running compared to the RFS running during the first half of the stance phase. The average contact forces during this period increased by 41.7% at the ankle and 14.4% at the knee joint during FFS running. Peak ankle joint contact force was 1.5 body weights greater during FFS running (p<0.05). There was no evidence to support a difference between habitual and converted running for joint contact forces. The increased loading at the ankle joint for FFS is an area of concern for individuals considering altering their foot strike pattern.     

Climate change and livestock parasites: integrated management of sheep blowfly strike in a warmer environment

The incidence of parasite‐mediated livestock disease is the result of a complex interaction of factors such as parasite and host abundance, host susceptibility, climate and, critically, farmer husbandry and intervention strategies, all of which change seasonally in space and time. Given the complexity of the interacting factors, the effects of environment changes on disease incidence are hard to predict, as accordingly are the optimal husbandry responses required to ameliorate any effects. Here a model system is used to explore these issues. Cutaneous myiasis (blowfly strike) is common disease of livestock and would be expected to be highly sensitive to even small changes in climate; it provides a good model for highlighting the problems inherent in attempting to predict the effect of climate change on livestock disease incidence. For this, a stochastic simulation model is used to examine the changes in the seasonal incidence of ovine cutaneous myiasis on farms in the United Kingdom and the likely effects of changes in husbandry and control strategies. The simulations show that the range of elevated temperatures predicted by current climate change scenarios result in an elongated blowfly season with earlier spring emergence and a higher cumulative incidence of strike. Overall, higher temperatures increased strike incidence disproportionately in ewes in early summer, but had relatively less direct effect on the pattern of lamb strike incidence; a +3 °C increase in average temperature approximately doubles the cumulative incidence of strike in lambs but results in four times more strikes in ewes. A range of strike management options is examined and the models show that changes in husbandry practices are also likely to have an important effect in reducing early season ewe strike incidences. The simulations suggest that integrated changes in husbandry practices are likely to be able to manage expected increases in strike, given the range of climate changes currently predicted.