Do Humans Prefer Faces? Zygomatic Muscle Responses to Neutral Faces vs. Neutral Objects

The present study examined the significance of viewing images of neutral faces versus images of neutral objects on zygomatic muscle activity using facial EMG. Participants (60% women) from a pool of introductory psychology courses had their facial EMG recordings measured in response to images of neutral faces and neutral objects. Participants’ valence rating of each image was also recorded using the Self-Assessment Manikin (SAM) in order to rate their emotional response to each image. The primary hypothesis was that participants would have greater activity in the zygomatic muscle region when presented with images of neutral faces as opposed to lessor activity when presented with images of neutral objects. It was also hypothesized that if participants preferred seeing images of faces as compared to objects, their positive feelings would produce higher SAM ratings. Results from the present study indicated images of neutral faces showed no significant difference in EMG activity compared to images of neutral objects. Self-report data also showed no significant difference in pleasantness or emotional valence between ratings of neutral faces and ratings of neutral objects

Flow Generation by Rotating Colloids in Planar Microchannels

Non-equilibrium structure formation and conversion of spinning to translational motion of magnetic colloids driven by an external rotating magnetic field in microchannels is studied by particle-based mesoscale hydrodynamics simulations. For straight channels, laning is found. In ring channels, the channel curvature breaks symmetry and leads to a net fluid transport around the annulus with the same rotational direction as the colloidal spinning direction. The dependence of the translational velocity on channel width, ring radius, colloid concentration, and thermal motion is predicted.Comment: http://epljournal.edpsciences.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/epl/abs/2010/24/epl13212/epl13212.htm

Structure-function relations in phosphorylcholine-binding mouse myeloma proteins

The binding site interactions between the phosphorylcholine (phosphocholine)-binding mouse myeloma proteins TEPC 15, W3207, McPC 603, MOPC 167, and MOPC 511 and the isotopically substituted hapten phosphoryl-[methyl-13C]choline have been investigated using 13C and 31P nuclear magnetic resonance (NMR) spectroscopy. Each protein exhibits a unique NMR pattern, but extensive similarities in chemical shift parameters upon binding of hapten to immunoglobulin suggest a significant degree of conservation of important hapten-binding site interactions. Moreover, independent binding studies, in conjunction with the NMR data, allow construction of a simple model of the binding sites of these antibodies, analyzed in terms of the relative strength of interaction between hapten and two main subsites. The NMR evidence supports the view that the heavy chains of these proteins dominate in interacting with bound phosphorylcholine; the various subspecificities of these proteins for phosphorylcholine analogues can be accounted for by amino acid changes in the hypervariable regions of the heavy chains

Laccase redox potentials: pH dependence and mutants, a QM/MM study

The authors are grateful for funding by the Engineering and Physical Sciences Research Council, grant “Clean catalysis for sustainable development” (Ref. EP/J018139/1).We have studied the T. versicolor laccase T1 site redox potential (RP) at the M06/6-311++G**/SDD(Cu) level of theory, employing QM/MM optimised geometries (RI-BP86/def2-SVP/def2-TZVP(Cu):CHARMM) of the whole protein system with electronic embedding. The oxidation state of the trinuclear cluster was found to affect the T1 site RP by about 0.2-0.3 V, depending on the protein protonation state. The computed laccase RP can be drastically lowered upon introduction of a protonation state corresponding to a neutral environment, by up to -1.37 V, which is likely an overestimation of the effect in vivo. The gradual change of the protonation state by single points without optimisation or equilibration results in a change that is even larger, namely up to about -2.6 V. Thus, the preferred protein conformation supports a high redox potential, compensating for the RP-lowering effect of surface charges. The predicted change in RP on going to the F463M mutant, ca. -0.1 V, is consistent with observations for a related laccase. Based on our results, we also propose and test a D206N mutant, but find it to be locked in a conformation with slightly lower RP.PostprintPeer reviewe

Do current-density nonlinearities cut off the glass transition?

Extended mode coupling theories for dense fluids predict that nonlinear current-density couplings cut off the singular `ideal glass transition', present in the standard mode coupling theory where such couplings are ignored. We suggest here that, rather than allowing for activated processes as sometimes supposed, contributions from current-density couplings are always negligible close to a glass transition. We discuss in schematic terms how activated processes can nonetheless cut off the transition, by causing the memory function to become linear in correlators at late times.Comment: 4 page

Ground-state ordering of the J1 - J2 model on the simple cubic and body-centered cubic lattices

The J1−J2 Heisenberg model is a “canonical” model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the coupled cluster method (CCM) to study the spin-half J1−J2 model with antiferromagnetic nearest-neighbor bonds J1>0 and next-nearest-neighbor bonds J2>0 for the simple cubic (sc) and body-centered cubic (bcc) lattices. In particular, we wish to study the ground-state ordering of these systems as a function of the frustration parameter p=z2J2/z1J1, where z1 (z2) is the number of nearest (next-nearest) neighbors. We wish to determine the positions of the phase transitions using the CCM and we aim to resolve the nature of the phase transition points. We consider the ground-state energy, order parameters, spin-spin correlation functions, as well as the spin stiffness in order to determine the ground-state phase diagrams of these models. We find a direct first-order phase transition at a value of p=0.528 from a state of nearest-neighbor Néel order to next-nearest-neighbor Néel order for the bcc lattice. For the sc lattice the situation is more subtle. CCM results for the energy, the order parameter, the spin-spin correlation functions, and the spin stiffness indicate that there is no direct first-order transition between ground-state phases with magnetic long-range order, rather it is more likely that two phases with antiferromagnetic long range are separated by a narrow region of a spin-liquid-like quantum phase around p=0.55. Thus the strong frustration present in the J1−J2 Heisenberg model on the sc lattice may open a window for an unconventional quantum ground state in this three-dimensional spin model