Implicit cognition is impaired and dissociable in a head-injured group with executive deficits

Implicit or non-conscious cognition is traditionally assumed to be robust to pathology but Gomez-Beldarrain et al (1999, 2002) recently showed deficits on a single implicit task after head injury. Laboratory research suggests that implicit processes dissociate. This study therefore examined implicit cognition in 20 head-injured patients and age- and I.Q.-matched controls using a battery of four implicit cognition tasks: a Serial Reaction Time task (SRT), mere exposure effect task, automatic stereotype activation and hidden co-variation detection. Patients were assessed on an extensive neuropsychological battery, and MRI scanned. Inclusion criteria included impairment on at least one measure of executive function. The patient group was impaired relative to the control group on all the implicit cognition tasks except automatic stereotype activation. Effect size analyses using the control mean and standard deviation for reference showed further dissociations across patients and across implicit tasks. Patients impaired on implicit tasks had more cognitive deficits overall than those unimpaired, and a larger Dysexecutive Self/Other discrepancy (DEX) score suggesting greater behavioural problems. Performance on the SRT task correlated with a composite measure of executive function. Head-injury thus produced heterogeneous impairments in the implicit acquisition of new information. Implicit activation of existing knowledge structures appeared intact. Impairments in implicit cognition and executive function may interact to produce dysfunctional behaviour after head-injury. Future comparisons of implicit and explicit cognition should use several measures of each function, to ensure that they measure the latent variable of interest

Relations between Kauffman and Homfly satellite invariants

We extend a mod 2 relation between the Kauffman and Homfly polynomials, first observed by Rudolph in 1987, to the general Kauffman and Homfly satellite invariants.Comment: 9 page

Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions

Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that heavy-ion fusion reactions are strongly affected by anharmonic properties of nuclear surface vibrations and nuclear shape, and thus provide a powerful method to study details of nuclear structure and dynamics.Comment: 8 pages, 5 figures, To be published in the Proceedings of the FUSION 97 Conference, South Durras, Australia, March 1997 (J. Phys. G

Continuity and Internal Properties of Gulf Coast Sandstones and their Implications for Geopressured Energy Development

The continuity of sandstone reservoirs is controlled by various factors including structural trend, sand-body geometry, and the distribution of framework grains, matrix, and interstices within the sand body. Except for the limits imposed by faults, these factors are largely inherited from the depositional environment and modified during sandstone compaction and cementation. Regional and local continuity of sandstone reservoirs depends on a depositional and structural hierarchy of four levels: (1) genetically related sandstones commonly associated with a single depositional system, (2) areally extensive fault blocks, (3) individual sandstones within a fault block, and (4) isolated reservoirs within a fault-bounded sandstone. Compilation of published and unpublished data for Tertiary and late Quaternary Gulf Coast sandstones of fluvial, deltaic, barrier-strandplain, and submarine fan origins suggests that volumes of sand systems (first hierarchical level) range from 10^11 to 10^13 ft^3, whereas volumes of individual sand bodies range from 10^9 to 10^11 ft^3. The continuity and productive limits of the ancient sandstones are substantially reduced by faults and internal heterogeneity that further subdivide the sand body into individual compartments. For the Wilcox and Frio trends of Texas, fault blocks (second hierarchical level) vary greatly in size, most being between 0.3 and 52 mi^2 in area; however, the distribution is strongly skewed toward small areas. Volumes of individual reservoirs (fourth hierarchical level) determined from engineering production data are 50 percent less to 200 percent more than estimates obtained from geologic mapping. In general, mapped volumes underestimate actual volumes where faults are non-sealing and overestimate actual volumes where laterally continuous shale breaks cause reductions in porosity and permeability.Bureau of Economic Geolog

Fusion barrier distributions in systems with finite excitation energy

Eigen-channel approach to heavy-ion fusion reactions is exact only when the excitation energy of the intrinsic motion is zero. In order to take into account effects of finite excitation energy, we introduce an energy dependence to weight factors in the eigen-channel approximation. Using two channel problem, we show that the weight factors are slowly changing functions of incident energy. This suggests that the concept of the fusion barrier distribution still holds to a good approximation even when the excitation energy of the intrinsic motion is finite. A transition to the adiabatic tunneling, where the coupling leads to a static potential renormalization, is also discussed.Comment: 9 pages, 4 figures, Submitted to Physical Review

Uncovering the topology of configuration space networks

The configuration space network (CSN) of a dynamical system is an effective approach to represent the ensemble of configurations sampled during a simulation and their dynamic connectivity. To elucidate the connection between the CSN topology and the underlying free-energy landscape governing the system dynamics and thermodynamics, an analytical soluti on is provided to explain the heavy tail of the degree distribution, neighbor co nnectivity and clustering coefficient. This derivation allows to understand the universal CSN network topology observed in systems ranging from a simple quadratic well to the native state of the beta3s peptide and a 2D lattice heteropolymer. Moreover CSN are shown to fall in the general class of complex networks describe d by the fitness model.Comment: 6 figure

Profiles

Short biographical sketches of Henry Whitcom Sweeney by A.N. Mosich, DR Scott by James R. Morton, John Bennett Canning by William Robert Smith, and F.R.M. de Paula by Stephen A. Zeff