Nucleation and motion of kink pairs on partial dislocations are examined by elasticity theory for materials with a high Peierls stress. Two approaches are used: one considers the change in average stacking-fault energy due to alloying elements and the other considers the change in local SFE due to a nearby solute atom. Both approaches highlight the role of SFE on kink nucleation, propagation and annihilation and both furnish strain rate as a function of stress, temperature and SFE. Model predictions are (...) compared with yield stress data for two systems: firstly, an intermetallic, MoSi 2 , which softens for alloying elements that decrease the SFE and hardens for Re additions that increase the SFE; secondly, a ceramic oxide, MgO-Al 2 O 3 spinel, which softens with increasing addition of excess alumina and at the same time exhibits a decrease in SFE. The average SFE approach agrees qualitatively with the data while quantitative agreement is obtained with the local SFE approach. The possibility is considered that the model applies to other materials, such as TiAl, HfV 2 and Fe 3 Al, which show softening with certain alloying additions. One requirement is that the dislocations are dissociated more than a few atomic distances; otherwise kink nucleation occurs on the perfect dislocation . Hence the model does not apply to materials such as bcc metals which only have a core dissociation. Normal hardening effects of solutes from size and modulus misfits are additive with any softening effects from a decrease in SFE and so may mask the latter, as occurs for W additions to MoSi 2. (shrink)

Background:Reducing the incidence and negative consequences of concussion among youth athletes is a public health priority. In 2010, Massachusetts passed legislation aimed at addressing the issue of concussions in school athletics. We sought to understand local-level implementation decisions of the Massachusetts concussion law.Methods:A qualitative multiple-case study approach was utilized. Semi-structured interviews with school-employed actors associated with the law's implementation were used for analysis. Interview data were subjected to a conventional content analysis.Results:A total of 19 participants from 5 schools were interviewed. (...) Schools were purposefully selected from communities varying in socioeconomic status and population. Participants included 5 athletic directors, 5 coaches, 4 athletic trainers, 4 school nurses, and 1 health and wellness coordinator. Eight themes emerged regarding specific ways schools have implemented the law. Six themes emerged regarding factors influencing implementation.Conclusions:All cases employ neurocognitive testing as a means to assess concussions, place decision-making authority in athletic trainers' hands, and use a 30-minute online video to disseminate concussion education. Employing athletic trainers could pose challenges to school districts with limited financial capacity, as financial assistance from the state is not provided under the law. The validity of neurocognitive testing and the effectiveness of online concussion training need further study. Cooperation from student athletes, their parents, and physicians is necessary for full implementation of the law. (shrink)

Reasoning well about risk is most challenging when a woman is pregnant, for patient and doctor alike. During pregnancy, we tend to note the risks of medical interventions without adequately noting those of failing to intervene, yet when it's time to give birth, interventions are seldom questioned, even when they don't work. Meanwhile, outside the clinic, advice given to pregnant women on how to stay healthy in everyday life can seem capricious and overly cautious. This kind of reasoning reflects fear, (...) not evidence. (shrink)

People may exhibit two kinds of modifications when demonstrating action for others: modifications to facilitate bottom‐up, or sensory‐based processing; and modifications to facilitate top‐down, or knowledge‐based processing. The current study examined actors' production of such modifications in action demonstrations for audiences that differed in their capacity for intentional reasoning. Actors' demonstrations of complex actions for a non‐anthropomorphic computer system and for people (adult and toddler) were compared. Evidence was found for greater highlighting of top‐down modifications in the demonstrations for the (...) human audiences versus the computer audience. Conversely, participants highlighted simple perceptual modifications for the computer audience, producing more punctuated and wider ranging motions. This study suggests that people consider differences in their audiences when demonstrating action. (shrink)

A major theme in rap lyrics is that the only way to survive is to use your head, be aware, know what’s going on around you. That simple idea packs a lot of background. The most obvious ideas about knowledge turn out if you look at them close up to be pretty questionable. For example: How do we get knowledge about the world? A natural and ancient answer to this question is that much if not all of our knowledge comes (...) from our senses. So for example the nose gives us knowledge of what things smell like, and if all goes well, also indicates whether the thing we’re smelling is healthy, tasty, or noxious. Likewise, the eyes tell us the color and shape of things, and thereby give us information about whether those things are useful, dangerous, and so on. Like everybody else, rappers know all this. Or do they? Maybe some rappers know that this isn’t really so. I’m not talking about Extra-Sensory Perception, channeling, auras, or about what. (shrink)

Mitchell: Could we begin by discussing the problem of public art? When we spoke a few weeks ago, you expressed some uneasiness with the notion of public art, and I wonder if you could expand on that a bit.Kruger: Well, you yourself lodged it as the “problem” of public art and I don’t really find it problematic inasmuch as I really don’t give it very much thought. I think on a broader level I could say that my “problem” is (...) with categorization and naming: how does one constitute art and how does one constitute a public? Sometimes I think that if architecture is a slab of meat, then so-called public art is a piece of garnish laying next to it. It has a kind of decorative function. Now I’m not saying that it always has to be that way—at all—and I think perhaps that many of my colleagues are working to change that now. But all too often, it seems the case.Mitchell: Do you think of your own art, insofar as it’s engaged with the commercial public sphere—that is, with advertising, publicity, mass media, and other technologies for influencing a consumer public—that it is automatically a form of public art? Or does it stand in opposition to public art?Kruger: I have a question for you: what is a public sphere which is an uncommercial public sphere? Barbara Kruger is an artist who works with words and pictures. W. J. T. Mitchell, editor of Critical Inquiry, is Gaylord Donnelly Distinguished Professor of English and art at the University of Chicago. (shrink)

One method for investigating the neurobiology of consciousness is to experimentally manipulate consciousness as a variable and then visualize the resultant functional brain changes with advanced imaging techniques. To begin investigation into this area, healthy volunteers underwent positron emission tomography scanning while listening to randomized word lists in both conscious and unconscious conditions. Following anaesthesia, subjects had no explicit memories. Nonetheless, subjects demonstrated implicit memory on a forced-choice test . These subsequent memory scores were correlated with regional brain metabolism measured (...) during encoding. Conscious recall and unconscious recognition memory demonstrated considerable anatomic overlap in correlating significantly with relative glucose metabolism in auditory verbal memory areas. However, only conscious recall correlated with mediodorsal thalamic nucleus activity; unconscious recognition memory did not. These findings suggest that conscious versus unconscious memory distinctions may depend on the presence or absence of correlated thalamic activity, and directly implicate the thalamus in the neurobiology of consciousness. (shrink)

There is general acknowledgement that both the anterior cingulate and orbitofrontal cortex are implicated in reinforcement-guided decision making, and emotion and social behaviour. Despite the interest that these areas generate in both the cognitive neuroscience laboratory and the psychiatric clinic, ideas about the distinctive contributions made by each have only recently begun to emerge. This reflects an increasing understanding of the component processes that underlie reinforcement- guided decision making, such as the representation of reinforcement expectations, the exploration, updating and representation (...) of action values, and the appreciation that choices are guided not just by the prospect of reward but also by the costs that action entails. Evidence is emerging to suggest that the anterior cingulate and orbitofrontal cortex make distinct contributions to each of these aspects of decision making. (shrink)

In a reflective and richly entertaining piece from 1979, Doug Hofstadter playfully imagined a conversation between ‘Achilles’ and an anthill (the eponymous ‘Aunt Hillary’), in which he famously explored many ideas and themes related to cognition and consciousness. For Hofstadter, the anthill is able to carry on a conversation because the ants that compose it play roughly the same role that neurons play in human languaging; unfortunately, Hofstadter’s work is notably short on detail suggesting how this magic might be achieved1. (...) Conversely in this paper - finally reifying Hofstadter’s imagination - we demonstrate how populations of simple ant-like creatures can be organised to solve complex problems; problems that involve the use of forward planning and strategy. Specifically we will demonstrate that populations of such creatures can be configured to play a strategically strong - though tactically weak - game of HeX (a complex strategic game).We subsequently demonstrate how tactical play can be improved by introducing a form of forward planning instantiated via multiple populations of agents; a technique that can be compared to the dynamics of interacting populations of social insects via the concept of meta-population. In this way although, pace Hofstadter, we do not establish that a meta-population of ants could actually hold a conversation with Achilles, we do successfully introduce Aunt Hillary to the complex, seductive charms of HeX. (shrink)

What is the interaction between storage and computation in language processing? What is the psychological status of grammatical rules? What are the relative strengths of connectionist and symbolic models of cognition? How are the components of language implemented in the brain? The English past tense has served as an arena for debates on these issues. We defend the theory that irregular past-tense forms are stored in the lexicon, a division of declarative memory, whereas regular forms can be computed by a (...) concatenation rule, which requires the procedural system. Irregulars have the psychological, linguistic and neuropsychological signatures of lexical memory, whereas regulars often have the signatures of grammatical processing. Furthermore, because regular inflection is rule-driven, speakers can apply it whenever memory fails. (shrink)

v. 1. Indii︠a︡ -- v. 2. Blizhniĭ i Sredniĭ Vostok -- v. 3. Kitaĭ.