bluuebunny/crossref_metadata_2025_split huggingface dataset:
A causal framework for integrating learning and reasoning
Authors: Lagnado David A. 
Published: April 2009

AbstractCan the phenomena of associative learning be replaced wholesale by a propositional reasoning system? Mitchell et al. make a strong case against an automatic, unconscious, and encapsulated associative system. However, their propositional account fails to distinguish inferences based on actions from those based on observation. Causal Bayes networks remedy this shortcoming, and also provide an overarching framework for both learning and reasoning. On this account, causal representations are primary, but associative learning processes are not excluded a priori.
Is there room for simple links in a propositional mind?
Authors: Livesey Evan J. , Harris Justin A. 
Published: April 2009

AbstractAgainst Mitchell et al.'s assertions, we argue that (1) the concordance between learning and awareness does not support any particular learning theory, (2) their propositional approach is at odds with examples of learned behaviours that contradict beliefs about causation, and (3) the relative virtues of the two approaches in terms of parsimony is more ambiguous than Mitchell et al. suggest.
Saliences, propositions, and amalgams: Emergent learning in nonhumans
Authors: Lyn Heidi , Rumbaugh Duane M. 
Published: April 2009

AbstractWe comment on the similarities and differences of Mitchell et al.'s framework for understanding classical and operant conditioning and the theoretical framework put forth by Rumbaugh et al. (2007). We propose that all nonhuman and human learning may be based on amalgams created by co-occurring stimuli that share their response-eliciting properties and that these amalgams may be propositional in nature.
The Proust effect and the evolution of a dual learning system
Authors: Matute Helena , Vadillo Miguel A. 
Published: April 2009

AbstractProust's madeleine illustrates the automatic nature of associative learning. Although we agree with Mitchell et al. that no compelling scientific proof for this effect has yet been reported in humans, evolutionary constraints suggest that it should not be discarded: There is no reason by which natural selection should favor individuals who lose a fast and automatic survival tool.
Undermining the foundations: Questioning the basic notions of associationism and mental representation
Authors: Morsella Ezequiel , Riddle Travis A. , Bargh John A. 
Published: April 2009

AbstractPerhaps the time has come to re-examine the basic notions of cognitive science. Together with previous challenges against associationism, the target article should be viewed as a call to arms to re-evaluate the empirical basis for contemporary conceptualizations of human learning and the notion of “mental representation,” a concept that has become too imprecise for describing the elements of cognition.
Is cultivating “biological blindness” a viable route to understanding behavioral phenomena?
Authors: Olsson Andreas , Öhman Ame 
Published: April 2009

AbstractMitchell et al. propose that associative learning in humans and other animals requires the formation of propositions by means of conscious and controlled reasoning. This approach neglects important aspects of current thinking in evolutionary biology and neuroscience that support the claim that learning, here exemplified by fear learning, neither needs to be conscious nor controlled.
The computational nature of associative learning
Authors: Schmajuk N. A. , Kutlu G. M. 
Published: April 2009

AbstractAn attentional-associative model (Schmajuk et al. 1996), previously evaluated against multiple sets of classical conditioning data, is applied to causal learning. In agreement with Mitchell et al.'s suggestion, according to the model associative learning can be a conscious, controlled process. However, whereas our model correctly predicts blocking following or preceding subadditive training, the propositional approach cannot account for those results.
The associative nature of human associative learning
Authors: Shanks David R. 
Published: April 2009

AbstractThe extent to which human learning should be thought of in terms of elementary, automatic versus controlled, cognitive processes is unresolved after nearly a century of often fierce debate. Mitchell et al. provide a persuasive review of evidence against automatic, unconscious links. Indeed, unconscious processes seem to play a negligible role in any form of learning, not just in Pavlovian conditioning. But a modern connectionist framework, in which “cognitive” phenomena are emergent properties, is likely to offer a fuller account of human learning than the propositional framework Mitchell et al. propose.
A one-system theory that is not propositional
Authors: Witnauer James E. , Urcelay Gonzalo P. , Miller Ralph R. 
Published: April 2009

AbstractWe argue that the propositional and link-based approaches to human contingency learning represent different levels of analysis because propositional reasoning requires a basis, which is plausibly provided by a link-based architecture. Moreover, in their attempt to compare two general classes of models (link-based and propositional), Mitchell et al. refer to only two generic models and ignore the large variety of different models within each class.
Measuring ISM fields using Pulsars
Authors: Noutsos Aristeidis 
Published: April 2009

AbstractThe sample of available Galactic pulsar rotation measures has proven an invaluable tool for measuring the direction and magnitude of the interstellar magnetic fields of our Galaxy. In this review, I present highlights of recent efforts to measure and map the Galactic magnetic field using pulsars. I give an overview of the analysis methods that were used by previous authors and underline the key results that have given us a clear picture of the magnetic field in certain regions of the Galaxy. This review also lays out the limitations of the present analysis methods and the observational difficulties that have so far hindered the study of the Galactic magnetic field with pulsars. Despite these difficulties, the continuous discovery of new pulsars in more and more sensitive surveys offer a continuous improvement on the existing knowledge of the Galactic magnetic field.
Magnetic fields, stellar feedback, and the geometry of H II regions
Authors: Ferland Gary J. 
Published: April 2009

AbstractMagnetic pressure has long been known to dominate over gas pressure in atomic and molecular regions of the interstellar medium. Here I review several recent observational studies of the relationships between the H+, H0 and H2 regions in M42 (the Orion complex) and M17. A simple picture results. When stars form they push back surrounding material, mainly through the outward momentum of starlight acting on grains, and field lines are dragged with the gas due to flux freezing. The magnetic field is compressed and the magnetic pressure increases until it is able to resist further expansion and the system comes into approximate magnetostatic equilibrium. Magnetic field lines can be preferentially aligned perpendicular to the long axis of quiescent cloud before stars form. After star formation and pushback occurs ionized gas will be constrained to flow along field lines and escape from the system along directions perpendicular to the long axis. The magnetic field may play other roles in the physics of the H II region and associated PDR. Cosmic rays may be enhanced along with the field and provide additional heating of atomic and molecular material. Wave motions may be associated with the field and contribute a component of turbulence to observed line profiles.
Magnetic fields in Planetary Nebulae: paradigms and related MHD frontiers
Authors: Blackman Eric G. 
Published: April 2009

AbstractMany, if not all, post AGB stellar systems swiftly transition from a spherical to a powerful aspherical pre-planetary nebula (pPNE) outflow phase before waning into a PNe. The pPNe outflows require engine rotational energy and a mechanism to extract this energy into collimated outflows. Just radiation and rotation are insufficient but a symbiosis between rotation, differential rotation and large scale magnetic fields remains promising. Present observational evidence for magnetic fields in evolved stars is suggestive of dynamically important magnetic fields, but both theory and observation are rife with research opportunity. I discuss how magnetohydrodynamic outflows might arise in pPNe and PNe and distinguish different between approaches that address shaping vs. those that address both launch and shaping. Scenarios involving dynamos in single stars, binary driven dynamos, or accretion engines cannot be ruled out. One appealing paradigm involves accretion onto the primary post-AGB white dwarf core from a low mass companion whose decaying accretion supply rate owers first the pPNe and then the lower luminosity PNe. Determining observational signatures of different MHD engines is a work in progress. Accretion disk theory and large scale dynamos pose many of their own fundamental challenges, some of which I discuss in a broader context.
The source of magnetic fields in (neutron-) stars
Authors: Spruit Hendrik C. 
Published: April 2009

AbstractSome arguments, none entirely conclusive, are reviewed about the origin of magnetic fields in neutron stars, with emphasis of processes during and following core collapse in supernovae. Possible origins of the magnetic fields of neutron stars include inheritance from the main sequence progenitor and dynamo action at some stage of evolution of progenitor. Inheritance is not sufficient to explain the fields of magnetars. Energetic considerations point to differential rotation in the final stages of core collapse process as the most likely source of field generation, at least for magnetars. A runaway phase of exponential growth is needed to achieve sufficient field amplification during relevant phase of core collapse; it can probably be provided by a some form of magnetorotational instability. Once formed in core collapse, the field is in danger of decaying again by magnetic instabilities. The evolution of a magnetic field in a newly formed neutron star is discussed, with emphasis on the existence of stable equilibrium configurations as end products of this evolution, and the role of magnetic helicity in their existence. A particularly puzzling problem is the large range of field strengths observed in neutron stars (as well as in A stars and white dwarfs). It implies that a single, deterministic process is insufficient to explain the origin of the magnetic fields in these stars.
A galaxy dynamo by Supernova-driven interstellar turbulence
Authors: Gressel Oliver , Ziegler Udo , Elstner Detlef , Rüdiger Günther 
Published: April 2009

AbstractSupernovae are the dominant energy source for driving turbulence within the interstellar plasma. Until recently, their effects on magnetic field amplification in disk galaxies remained a matter of speculation. By means of self-consistent simulations of supernova-driven turbulence, we find an exponential amplification of the mean magnetic field on timescales of a few hundred million years. The robustness of the observed fast dynamo is checked at different magnetic Reynolds numbers, and we find sustained dynamo action at moderate Rm. This indicates that the mechanism might indeed be of relevance for the real ISM.Sensing the flow via passive tracer fields, we infer that SNe produce a turbulent α effect which is consistent with the predictions of quasilinear theory. To lay a foundation for global mean-field models, we aim to explore the scaling of the dynamo tensors with respect to the key parameters of our simulations. Here we give a first account on the variation with the supernova rate.
Dynamically dominant magnetic fields in the diffuse interstellar medium
Authors: Fletcher Andrew , Korpi M. , Shukurov A. 
Published: April 2009

AbstractObservations show that magnetic fields in the interstellar medium (ISM) often do not respond to increases in gas density as would be naively expected for a frozen-in field. This may suggest that the magnetic field in the diffuse gas becomes detached from dense clouds as they form. We have investigated this possibility using theoretical estimates, a simple magneto-hydrodynamic model of a flow without mass conservation and numerical simulations of a thermally unstable flow. Our results show that significant magnetic flux can be shed from dense clouds as they form in the diffuse ISM, leaving behind a magnetically dominated diffuse gas.
GMIMS: the Global Magneto-Ionic Medium Survey
Authors: Wolleben Maik , Landecker T. L. , Carretti E. , Dickey J. M. , Fletcher A. , Gaensler B. M. , Han J. L. , Haverkorn M. , Leahy J. P. , McClure-Griffiths N. M. , McConnell D. , Reich W. , Taylor A. R. 
Published: April 2009

AbstractThe Global Magneto-Ionic Medium Survey (GMIMS) is a project to map the diffuse polarized emission over the entire sky, Northern and Southern hemispheres, from 300 MHz to 1.8 GHz. With an angular resolution of 30–60 arcmin and a frequency resolution of 1 MHz or better, GMIMS will provide the first spectro-polarimetric data set of the large-scale polarized emission over the entire sky, observed with single-dish telescopes. GMIMS will provide an invaluable resource for studies of the magneto-ionic medium of the Galaxy in the local disk, halo, and its transition.
Magnetic fields in massive star forming regions: wide-field NIR polarimetry of M42 and Mon R2
Authors: Kusakabe Nobuhiko , Tamura Motohide , Kandori Ryo ,   the IRSF/SIRPOL group
Published: April 2009

AbstractMagnetic fields are believed to play an important role in star formation. We observed M42 and Mon R2 massive star forming regions using the wide-field (8′ × 8′) near-infrared imaging polarimeter SIRPOL in South Africa. Magnetic fields are mapped on the basis of dichroic polarized light from hundreds of young stars embedded in the regions. We found “hourglass shaped” magnetic field structure toward OMC-1 region, which is very consistent with magnetic fields traced by using dust emission polarimetry at sub-mm to FIR wavelengths. In the Mon R2 region, we found “S-shaped” magnetic field structure across the massive protostar IRS 1 and IRS 2. We will present the results of comparison of magnetic fields at NIR with those at other wavelengths.
Distortion of magnetic fields in the pre-stellar core Barnard 68
Authors: Kandori Ryo , Tamura Motohide , Tatematsu Ken-ichi , Kusakabe Nobuhiko , Nakajima Yasushi ,   the IRSF/SIRPOL group
Published: April 2009

AbstractMagnetic fields are believed to play an important role in controlling the stability and contraction of molecular cloud cores. In the present study, magnetic fields of a cold pre-stellar core, Barnard 68, have been mapped based on wide-field near-infrared polarimetric observations of background stars. A distinct “hourglass-shaped” magnetic field is identified toward the core, as the observational evidence of magnetic field structure distorted by mass accumulation in a pre-stellar core. Our findings on the geometry of magnetic fields as well as the mass-to-magnetic flux ratio are presented.
3D global MHD simulations of a proto-planetary disk: dead zone and large-scale magnetic fields
Authors: Dzyurkevich Natalia , Flock Mario , Klahr Hubert 
Published: April 2009

AbstractWe present 3D global MHD simulations of proto-planetary disks calculated with the ZeusMP code. We focus on gas dynamics; the magnetic diffusivity and temperature are fixed during the simulation. A zone with low gas ionization at the midplane is included within ±2 scale heights. We mimic the ‘snow’-line radius with one order of magnitude jump in magnetic diffusivity η. Resulting turbulent Maxwell and Reynolds stresses are present at the midplane despite of low ionization. We find no radial inhomogeneities in turbulent α stress for a mild ionization contrast at the ‘snow’-line. A smooth azimuthal magnetic field is produced in the dead zone which may be a driving force for a weak accretion flow.
Dead zone formation and non-steady hyperaccretion in collapsar disks
Authors: Masada Youhei 
Published: April 2009

AbstractIn ultra dense and hot region realized in stellar core-collapse, neutrino takes major role in energy and momentum transports. We investigate the growth of magnetorotational instability (MRI) in neutrino viscous matter by using linear theory. It is found from the local linear analysis that the neutrino viscosity can suppress the MRI in the regime of weak magnetic field (B ≪ 1014G). This suggest that MHD turbulence sustained by the MRI might not be driven efficiently in the neutrino viscous media. Applying this result to collapsar disk, which is known as the central engine of gamma-ray burst (GRB), we find that the MRI can be suppressed only in its inner region. Based on this finding, a new evolutionary scenario of collapsar disk, “Episodic Disk Accretion Model” are proposed.
Large solar-type magnetic reconnection model for magnetar giant flare
Authors: Masada Youhei 
Published: April 2009

AbstractWe construct a magnetic reconnection model for magnetar giant flare in the framework of solar flare/coronal mass ejection theory. As is the case with the solar flare, the explosive magnetic reconnection plays a crucial role in the energetics of the magnetar flare. A key physics controlling the energy transport in the system, on the other hand, is the radiative process unlike that in the solar flare. After the release of the magnetic energy via the magnetic reconnection, the radiative heat flux drives the baryonic evaporation. Our model can predict that the baryonic matter evaporated in the preflare stage would be the origin of the radio emitting ejecta observed in association with the giant flare on 2004 December 27 from SGR1806-20.
Surface magnetic fields in pulsars
Authors: Melikidze George I. , Gil Janusz 
Published: April 2009

AbstractObservations of hot-spot thermal X-ray emission from radio pulsars implicate that surface magnetic field (SMF) at the polar cap is much stronger than the conventional dipolar component estimated from the pulsar spin-down. This strongly suggests that SMF is dominated by the crust anchored small scale magnetic field. We present the observed values of black body temperature and bolometric luminosity of X-ray emission from hot polar caps of a number of pulsars. In all cases the inferred value of SMF is close to 1014 G.
Evidence of a magnetic sheath around a jet from NGC 6543
Authors: Meinel Aden B. , Meinel Barbara 
Published: April 2009

AbstractWe present observational evidence that NGC 6543 produced a jet of cosmic rays that irradiated the Earth recorded as cosmogenic10Be found ice cores. This identification shows that the jet was accompanied by a magnetic field of sufficient strength to travel 220pc and retain evidence of the celestial coordinates of the source object.
On the relation between photospheric magnetic field and chromospheric emission in the quiet Sun
Authors: Loukitcheva Maria A. , Solanki Sami K. , White Stephen M. 
Published: April 2009

AbstractIn this contribution we present an observational study of the interaction of the photosphere with different chromospheric layers. We study the correlations between emissions at varying temperature from the temperature minimum region (UV continuum at 1600 Å from TRACE) through the low chromosphere (CaII K-line from BBSO) to the middle chromosphere (continuum at 3.5 mm from BIMA) and photospheric magnetic field from MDI/SOHO. For the first time millimeter observational data are included in such analysis.We report a high degree of correlation between considered emissions formed at different heights in the chromosphere. A power law is found to be a good representation for the relationship between photospheric magnetic field and chromospheric emissions at all considered wavelengths. Our analysis shows that the dependence of chromospheric intensities on magnetic field is different for the network and internetwork regions. In the network a power law provides the best fit with the exponent being close to 0.5–0.6, while almost no dependence of chromospheric intensity on magnetic flux is found for the cell interiors. The obtained results support the idea of different heating mechanisms acting in the network (magnetic) and cell interiors (acoustic).
The second solar spectrum and the hidden magnetism
Authors: Stenflo Jan O. 
Published: April 2009

AbstractApplications of the Hanle effect have revealed the existence of vast amounts of “hidden“ magnetic flux in the solar photosphere, which remains invisible to the Zeeman effect due to cancellations inside each spatial resolution element of the opposite-polarity contributions from this small-scale, tangled field. The Hanle effect is a coherency phenomenon that represents the magnetic modification of the linearly polarized spectrum of the Sun that is formed by coherent scattering processes. This so-called “Second Solar Spectrum” is as richly structured as the ordinary intensity spectrum, but the spectral structures look completely different and have different physical origins. One of the new diagnostic uses of this novel spectrum is to explore the magnetic field in previously inaccessible parameter domains. The earlier view that most of the magnetic flux in the photosphere is in the form of intermittent kG flux tubes with tiny filling factors has thereby been shattered. The whole photospheric volume instead appears to be seething with intermediately strong fields, of order 100G, of significance for the overall energy balance of the solar atmosphere. According to the new paradigm the field behaves like a fractal with a high degree of self-similarity between the different scales. The magnetic structuring is expected to continue down to the 10m scale, 4 orders of magnitude below the current spatial resolution limit.
Mini-filaments – small-scale analogues of solar eruptive events?
Authors: Denker Carsten , Tritschler Alexandra 
Published: April 2009

AbstractMini-filaments are a small-scale phenomenon of the solar chromosphere, which frequently occur across the entire disk (see e.g. Wang, Li, Denker, et al. 2000). They share a variety of characteristics with their larger-scale cousins and may serve as a proxy for more complex systems. They play an important role in the energy and mass supply to the corona. In the case of small-scale eruptive filaments, only a single, small-scale loop system is involved. Furthermore, they are supported by simple magnetic field configurations (see Livi, Wang & Martin 1985), either magnetic bipoles or well-defined multipoles, easing their theoretical description. Since mini-filaments are small (just a few tens of seconds of arc) but highly dynamic (eruptions can occur within just a few minutes), they are an ideal target for high-resolution two-dimensional spectroscopy. We present a preliminary analysis of two-dimensional Hα spectroscopic data accompanied by broad-band speckle-restored images to demonstrate that chromospheric small-scale phenomena can serve as building blocks for our understanding of solar eruptive events such as filament/prominence eruptions and even coronal mass ejections (CMEs).