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Search Results: 1 - 10 of 402026 matches for " Kirsten M. VanMeenen "
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Learning to Obtain Reward, but Not Avoid Punishment, Is Affected by Presence of PTSD Symptoms in Male Veterans: Empirical Data and Computational Model
Catherine E. Myers, Ahmed A. Moustafa, Jony Sheynin, Kirsten M. VanMeenen, Mark W. Gilbertson, Scott P. Orr, Kevin D. Beck, Kevin C. H. Pang, Richard J. Servatius
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0072508
Abstract: Post-traumatic stress disorder (PTSD) symptoms include behavioral avoidance which is acquired and tends to increase with time. This avoidance may represent a general learning bias; indeed, individuals with PTSD are often faster than controls on acquiring conditioned responses based on physiologically-aversive feedback. However, it is not clear whether this learning bias extends to cognitive feedback, or to learning from both reward and punishment. Here, male veterans with self-reported current, severe PTSD symptoms (PTSS group) or with few or no PTSD symptoms (control group) completed a probabilistic classification task that included both reward-based and punishment-based trials, where feedback could take the form of reward, punishment, or an ambiguous “no-feedback” outcome that could signal either successful avoidance of punishment or failure to obtain reward. The PTSS group outperformed the control group in total points obtained; the PTSS group specifically performed better than the control group on reward-based trials, with no difference on punishment-based trials. To better understand possible mechanisms underlying observed performance, we used a reinforcement learning model of the task, and applied maximum likelihood estimation techniques to derive estimated parameters describing individual participants’ behavior. Estimations of the reinforcement value of the no-feedback outcome were significantly greater in the control group than the PTSS group, suggesting that the control group was more likely to value this outcome as positively reinforcing (i.e., signaling successful avoidance of punishment). This is consistent with the control group’s generally poorer performance on reward trials, where reward feedback was to be obtained in preference to the no-feedback outcome. Differences in the interpretation of ambiguous feedback may contribute to the facilitated reinforcement learning often observed in PTSD patients, and may in turn provide new insight into how pathological behaviors are acquired and maintained in PTSD.
Vaarwel aan etnosentrisme*
J. M. Kirsten
Koers : Bulletin for Christian Scholarship , 1981, DOI: 10.4102/koers.v46i2.1087
Abstract: In this article the author deals with the problem of ethnocentrism within the framework of the larger problem of primitivity and modernity. Ethnocentrism strats from the premise of a normative comparison between primitive and modern cultures on the basis of inter-cultural criteria which are determined by the idiosyncratic cultural situation. This comparison must inevitably culminate in a self-centred glorification of the idiosyncratic national and group traditions and values This dilemma may be avoided, according to the author, should primitivity and modernity not be regarded as two normatively different ways of life (in the sense that the latter should necessarily be better or higher than the preceding one), but as alternative cultural strategies. Primitivity and modernity are cultural strategies oriented in and directed at totally divergent value systems. It is methodologically incorrect to measure the one in terms of the other. There are no logical or ethical grounds to regard the technical and scientific develop- ment of Western civilization (that is, in terms of cultural values more highly than the so-called primitive cultures. In fact, Western (utilitarian) value orientation is in itself suspect. The motif of technico-scientific control underlying this goes hand in hand with control and stewardship of man himself. Western man has in fact come into the point: where he himself is becoming the victim of his own uncontrollable urge for power.
Afskeid van die moderne wereld? ’n Oorsig van die postm kultuurkritiek 1
J. M. Kirsten
Koers : Bulletin for Christian Scholarship , 1987, DOI: 10.4102/koers.v52i1- 4.915
Abstract: What has come to be called 'postmodernism', it is argued along Habermasian lines, Is based on the claim to have gone beyond the cultural framework of Western rationality and to have left it behind as the horison of an obsolete tradition. As such it represents a sweeping epochal self-characterisation in which modernity and the achievements of en- lightened reason are abandoned. The aim of the paper is to provide a broad outline of the postmodern theorem through a conceptual clarification of the different terminological variations in which 'modern'/'post-modern' appears. Firstly, the term 'modern' is analysed with a view to deter- mining the principles which have since become the target of postmodernist critique. Next, the analyses of ’modernity’, 'modernism' and 'modernisation' are utilised to establish the philosophical, aesthetic and sociological discourses on modernity as the main discursive contexts in which the critique of Western logocentrism is articulated. Finally, the term ’postmodernism’ is analysed in order to formulate a provisional conclusion concerning the nature of the postmodernist rejection of modernity. It is suggested that postmodernism represents a revolt against modernity rather than a genuine abandonment of its presuppositions.
Wat is kultuur? 'n Filosofiese antwoord
J. M. Kirsten
Koers : Bulletin for Christian Scholarship , 1984, DOI: 10.4102/koers.v49i3.1075
Abstract: The essay offers a philosophical answer to the traditional question concerning the "essence" of culture. A descriptive procedure is adopted whereby the phenomenon of culture is approached from two different, but interrelated perspectives. First of all a cross section is made of the structure of culture in order to describe the phenomenon in its unity. From this dioramic perspective culture is defined as the transcendence of nature by man on the basis of strategic actions which subject both nature and man himself to new and never-changing forms. Secondly an overview is given of the context of culture in order to describe it in its totality. From a panoramic viewpoint, it is suggested, culture refers to history as the encompassing context in which dwelling man moves towards the world of the future through the continuous re-working of his present abode.
Neomarxisme — Kultuurkritiek tussen die Mislukking van die revolusie in die ooste en die versuim van die revolusie in die Weste
J. M. Kirsten
Koers : Bulletin for Christian Scholarship , 1982, DOI: 10.4102/koers.v47i3.1025
Abstract: This introduction to "Neomarxism” begins by a formal analysis of the concept itself. It is suggested here that this term refers to the philosophical revival and revision of Marxist theory in the West. The philosophic-historical context of Neomarxism is consequently outlined so as to elucidate the basic elements of this revision. It appears that this context is determined by the dual experience of the betrayed revolution in the East and the abandoned revolution in the West. Against this background an explanation is then given as to why Neomarxist criticism of Marx concentrates especially on the so-called reductivist and deterministic elements in historical materialism. Finally the leitmotif of the Neomarxist critique of culture is defined. Their rejection of the technocratic ideal of progress not only demonstrates their departure from Marx and the Marxist belief in the emancipatory effect of the rational control of nature. In addition it justifies the view that a radical critique of Marx simultaneously implies a critique of the very roots of modern Western society.
Heat-kernel coefficients of the Laplace operator on the 3-dimensional ball
K. Kirsten,M. Bordag
Physics , 1995,
Abstract: We consider the heat-kernel expansion of the massive Laplace operator on the three dimensional ball with Dirichlet boundary conditions. Using this example, we illustrate a very effective scheme for the calculation of an (in principle) arbitrary number of heat-kernel coefficients for the case where the basis functions are known. New results for the coefficients $B_{\frac 5 2},...,B_5$ are presented.
Vacuum energy in a spherically symmetric background field
M. Bordag,K. Kirsten
Physics , 1996, DOI: 10.1103/PhysRevD.53.5753
Abstract: The vacuum energy of a scalar field in a spherically symmetric background field is considered. It is expressed through the Jost function of the corresponding scattering problem. The renormalization is discussed in detail and performed using the uniform asymptotic expansion of the Jost function. The method is demonstrated in a simple explicit example.
The ground state energy of a spinor field in the background of a finite radius flux tube
M. Bordag,K. Kirsten
Physics , 1998, DOI: 10.1103/PhysRevD.60.105019
Abstract: We develop a formalism for the calculation of the ground state energy of a spinor field in the background of a cylindrically symmetric magnetic field. The energy is expressed in terms of the Jost function of the associated scattering problem. Uniform asymptotic expansions needed are obtained from the Lippmann-Schwinger equation. The general results derived are applied to the background of a finite radius flux tube with a homogeneous magnetic field inside and the ground state energy is calculated numerically as a function of the radius and the flux. It turns out to be negative, remaining smaller by a factor of $\alpha$ than the classical energy of the background except for very small values of the radius which are outside the range of applicability of QED.
Heat kernel Coefficients and Divergencies of the Casimir Energy for the Dispersive Sphere
M. Bordag,K. Kirsten
Physics , 2001, DOI: 10.1142/S0217751X02010170
Abstract: The first heat kernel coefficients are calculated for a dispersive ball whose permittivity at high frequency differs from unity by inverse powers of the frequency. The corresponding divergent part of the vacuum energy of the electromagnetic field is given and ultraviolet divergencies are seen to be present. Also in a model where the number of atoms is fixed the pressure exhibits infinities. As a consequence, the ground-state energy for a dispersive dielectric ball cannot be interpreted easily.
Plasma-Etching of the Organic Layer in Nacre  [PDF]
Kirsten Parratt, Johnathan M. Yao, Gerald R. Poirier, Nan Yao
Soft Nanoscience Letters (SNL) , 2014, DOI: 10.4236/snl.2014.43009
Abstract:

Nacre’s brick and mortar structure has been motivating innovations in biomimetic materials for decades. However, there is still room to improve understanding of the structure of the organic layer in order to engineer better biomimetic composites. A plasma-etching technique that allows for the selective removal of some organic components from individual layers is developed. We conclude that this technique enables a closer examination of the organic layer such that the locations and mechanical properties of individual components can be determined. A methodology for examining nacre samples that have not been demineralized provides a more accurate substrate for understanding the structure-property relationships of the organic layer in native nacre.

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