Steady and nonsteady supersonic turbulent afterbody flow

The effect of the specific heat ratio gamma of the incoming ideal gas on the flow properties, especially on pressure distributions along the base and sting surfaces and on reattachment distance, was investigated. The specific heat ratios considered were gamma = 1.2, 1.4, and 1.667. Also, effects of other major parameters, such as eddy-viscosity coefficient (or effective Reynolds number) and Mach number, on the afterbody pressure and reattachment distance were studied and are discussed. Evolution of shock induced flow and stabilization time were examined and are discussed for a transient problem. The important influence of the flow-field geometry, pressure distributions, and reattachment distance on the aerodynamics radiative heat transfer for an atmosphere entry probe in high speed flight are briefly described

Introduction: the invisible (migrant) man

Migration scholarship has often lagged behind developments in gender studies. The importance of gender has gained increasing recognition but this has predominantly meant a focus on women migrants; only recently has agendered lens been turned to the study of migrant men. Discourses surrounding migrationin law andgovernment, and in legal scholarship, remain characterised by neglect or dismissal of the gendered experiences of male migrants. Where they do appear, men are frequently cast as the oppressor of family members or as abusing legal channels of migration. Their vulnerabilities and affective ties and needs are rarely foregrounded. This negative representation may be instrumentalizedat a variety of levels, and for a variety of purposes, making it difficult for more nuanced critiques to gain purchase.This Special Issue seeks to extend the discussion of migration and gender by exploring the ways in which men’s gendered experiences of migration remain marginalised

"The Case Against Intergenerational Accounting: The Accounting Campaign Against Social Security and Medicare"

The Federal Accounting Standards Advisory Board (FASAB) has proposed subjecting the entire federal budget to "intergenerational accounting"--which purports to calculate the debt burden our generation will leave for future generations--and is soliciting comments on the recommendations of its two "exposure drafts." The authors of this brief find that intergenerational accounting is a deeply flawed and unsound concept that should play no role in federal government budgeting, and that arguments based on this concept do not support a case for cutting Social Security or Medicare. The FASAB exposure drafts have not made a persuasive argument about basic matters of accounting, say the authors. Federal budget accounting should not follow the same procedures adopted by households or business firms because the government operates in the public interest, with the power to tax and issue money. There is no evidence, nor any economic theory, behind the proposition that government spending needs to match receipts. Social Security and Medicare spending need not be politically constrained by tax receipts--there cannot be any "underfunding." What matters is the overall fiscal stance of the government, not the stance attributed to one part of the budget.

Problems with Using Evolutionary Theory in Philosophy

Does science move toward truths? Are present scientific theories (approximately) true? Should we invoke truths to explain the success of science? Do our cognitive faculties track truths? Some philosophers say yes, while others say no, to these questions. Interestingly, both groups use the same scientific theory, viz., evolutionary theory, to defend their positions. I argue that it begs the question for the former group to do so because their positive answers imply that evolutionary theory is warranted, whereas it is self-defeating for the latter group to do so because their negative answers imply that evolutionary theory is unwarranted

Key Challenges and Potential Urban Modelling Opportunities in South Africa, with Specific Reference to the Gauteng City-Region

Urban growth and land use change models, supported by Geographic Information Systems (GIS) software and increased digital data availability, have the potential to become important tools for monitoring and guiding urban spatial planning and development. Five broad categories of urban models are utilised internationally, that is, land use transportation models, cellular automata, system dynamics, agent-based models and spatial economics/econometric models. This paper provides a broad overview of South African modelling projects that monitor or simulate urban spatial change. The review identified a variety of government and academic urban modelling initiatives. These initiatives mostly track trends, rather than simulating future scenarios, and analyse historical land cover change using GIS and remote sensing software. There is a risk within Gauteng, however, that out-dated data, different population projections, duplicated tools, limited spatial data infrastructure (SDI) and a lack of resources; could compromise urban spatial change modelling efforts within government institutions. As such, the paper discusses key challenges and opportunities for modelling urban spatial change, with specific reference to the Gauteng City-Region – the heartland of the South African economy and the Southern African region

Polar relaxation by dynein-mediated removal of cortical myosin II

Nearly 6 decades ago, Lewis Wolpert proposed the relaxation of the polar cell cortex by the radial arrays of astral microtubules as a mechanism for cleavage furrow induction (White and Borisy, 1983; Wolpert, 1960). While this mechanism has remained controversial (Rappaport, 1996), recent work has provided evidence for polar relaxation by astral microtubules (Chen et al., 2008; Dechant and Glotzer, 2003; Foe and Dassow, 2008; Murthy and Wadsworth, 2008; Werner et al., 2007), although its molecular mechanisms remain elusive. Here, using C. elegans embryos, we show that polar relaxation is achieved through dynein-mediated removal of myosin II from the polar cortexes. Mutants that position centrosomes closer to the polar cortex accelerated furrow induction whereas suppression of dynein activity delayed furrowing. We provide evidence that dynein-mediated removal of myosin II from the polar cortexes triggers cortical flow towards the cell equator, which induces the assembly of the actomyosin contractile ring. These studies for the first time provide a molecular basis for the aster-dependent polar relaxation, which works in parallel with equatorial stimulation to promote robust cytokinesis

Retractions in Science

Publication plays a pivotal role in the growth and dissemination of scientific knowledge. But the growth of knowledge is neither strictly linear nor unidirectional. Mistakes are made. Retraction is one means by which the scientific record is corrected. In this paper, we examine the retraction practices and prevalence in the journal Science. We focus on 35 years of published retractions, from 1983 to 2017. We are not only concerned with determining the scope of the problem, but also the patterns in the data. From a policy perspective, knowledge of any patterns in retractions may be useful in developing targeted responses to deal with the root causes