bluuebunny/crossref_metadata_2025 huggingface dataset:
Tuning effective interactions close to the critical point in colloidal suspensions
Authors: Gnan Nicoletta , Zaccarelli Emanuela , Sciortino Francesco
Published: August 2012

We report a numerical investigation of two colloids immersed in a critical solvent, with the aim of quantifying the effective colloid-colloid interaction potential. By turning on an attraction between the colloid and the solvent particles we follow the evolution from the case in which the solvent density close to the colloids changes from values smaller than the bulk to values larger than the bulk. We thus effectively implement the so-called (+, +) and (−, −) boundary conditions defined in field theoretical approaches focused on the description of critical Casimir forces. We find that the effective potential at large distances decays exponentially, with a characteristic decay length compatible with the bulk critical correlation length, in full agreement with theoretical predictions. We also investigate the case of (+, −) boundary condition, where the effective potential becomes repulsive. Our study provides a guidance for a design of the interaction potential which can be exploited to control the stability of colloidal systems.
Molecular mass dependence of point-to-set correlation length scale in polymers
Authors: Hanson Ben , Pryamitsyn Victor , Ganesan Venkat
Published: August 2012

We use a recently proposed metric, termed the point-to-set correlation functions, to probe the molecular weight dependence of the relevant static length scales in glass-forming oligomeric chain liquids of 4, 5, 8, and 10 repeat units. In agreement with the results for simple, monatomic fluids, we find that static length scales of the oligomers increase monotonically when the temperature is lowered towards the glass transition temperature of the fluid. More interestingly, the static length scale increases with increasing chain length. Within the bounds of error in our simulations, the static length scale appears to scale as the radius of gyration of the oligomer, but with a prefactor, which is much larger than unity and which grows with the temperature. The preceding behavior contrasts with the length scales extracted from the radial distribution function of the oligomer system, which is practically independent of the chain length.
Correlated electron-nuclear dynamics: Exact factorization of the molecular wavefunction
Authors: Abedi Ali , Maitra Neepa T. , Gross E. K. U.
Published: August 2012

It was recently shown [A. Abedi, N. T. Maitra, and E. K. U. Gross, Phys. Rev. Lett. 105, 123002 (2010)]10.1103/PhysRevLett.105.123002 that the complete wavefunction for a system of electrons and nuclei evolving in a time-dependent external potential can be exactly factorized into an electronic wavefunction and a nuclear wavefunction. The concepts of an exact time-dependent potential energy surface (TDPES) and exact time-dependent vector potential emerge naturally from the formalism. Here, we present a detailed description of the formalism, including a full derivation of the equations that the electronic and nuclear wavefunctions satisfy. We demonstrate the relationship of this exact factorization to the traditional Born-Oppenheimer expansion. A one-dimensional model of the ${\rm H}_2^+$H2+ molecule in a laser field shows the usefulness of the exact TDPES in interpreting coupled electron-nuclear dynamics: we show how features of its structure indicate the mechanism of dissociation. We compare the exact TDPES with potential energy surfaces from the time-dependent Hartree-approach, and also compare traditional Ehrenfest dynamics with Ehrenfest dynamics on the exact TDPES.
Multi-state vibronic interactions in the 1,2,3-trifluorobenzene radical cation
Authors: Faraji Shirin , Köppel Horst
Published: August 2012

The multi-state and multi-mode vibronic interactions between the five lowest electronic states of the title compound are investigated theoretically by an ab initio quantum dynamical approach. The well-established linear vibronic coupling scheme is adopted, augmented by quadratic coupling terms for the totally symmetric modes. The pertinent system parameters are obtained from outer valence Greens function and equation-of-motion coupled-cluster ab initio calculations. Large-scale quantum dynamical simulations are performed employing a powerful wavepacket propagation scheme. The band shapes and line structures (as far as available) of the experimental photoelectron spectra are well reproduced. Time-dependent electronic populations reveal ultrafast internal conversion processes and allow for important insight into the fluorescence properties of the radical cation. The relation to other fluoro derivatives of the benzene radical cation is discussed.
Third order integrability conditions for homogeneous potentials of degree −1
Authors: Combot Thierry , Koutschan Christoph
Published: August 2012

We prove an integrability criterion of order 3 for a homogeneous potential of degree −1 in the plane. Still, this criterion depends on some integer and it is impossible to apply it directly except for families of potentials whose eigenvalues are bounded. To address this issue, we use holonomic and asymptotic computations with error control of this criterion and apply it to the potential of the form V(r, θ) = r−1h(exp (iθ)) with $h\in \mathbb {C}[z],\;\deg h \le 3$h∈C[z],degh≤3. We then find all meromorphically integrable potentials of this form.
Experimental and theoretical studies of the O(3P) + C2H4 reaction dynamics: Collision energy dependence of branching ratios and extent of intersystem crossing
Authors: Fu Bina , Han Yong-Chang , Bowman Joel M. , Leonori Francesca , Balucani Nadia , Angelucci Luca , Occhiogrosso Angela , Petrucci Raffaele , Casavecchia Piergiorgio
Published: August 2012

The reaction of O(3P) with C2H4, of importance in combustion and atmospheric chemistry, stands out as paradigm reaction involving not only the indicated triplet state potential energy surface (PES) but also an interleaved singlet PES that is coupled to the triplet surface. This reaction poses great challenges for theory and experiment, owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of the collision complexes. Crossed molecular beam (CMB) scattering experiments with soft electron ionization detection are used to disentangle the dynamics of this polyatomic multichannel reaction at a collision energy Ec of 8.4 kcal/mol. Five different primary products have been identified and characterized, which correspond to the five exothermic competing channels leading to H + CH2CHO, H + CH3CO, CH3 + HCO, CH2 + H2CO, and H2 + CH2CO. These experiments extend our previous CMB work at higher collision energy (Ec ∼ 13 kcal/mol) and when the results are combined with the literature branching ratios from kinetics experiments at room temperature (Ec ∼ 1 kcal/mol), permit to explore the variation of the branching ratios over a wide range of collision energies. In a synergistic fashion, full-dimensional, QCT surface hopping calculations of the O(3P) + C2H4 reaction using ab initio PESs for the singlet and triplet states and their coupling, are reported at collision energies corresponding to the CMB and the kinetics ones. Both theory and experiment find almost an equal contribution from the triplet and singlet surfaces to the reaction, as seen from the collision energy dependence of branching ratios of product channels and extent of intersystem crossing (ISC). Further detailed comparisons at the level of angular distributions and translational energy distributions are made between theory and experiment for the three primary radical channel products, H + CH2CHO, CH3 + HCO, and CH2 + H2CO. The very good agreement between theory and experiment indicates that QCT surface-hopping calculations, using reliable coupled multidimensional PESs, can yield accurate dynamical information for polyatomic multichannel reactions in which ISC plays an important role.
Synchrotron far infrared spectroscopy of the ground, ν5, and ν15 states of thiirane
Authors: Bane Michael K. , Thompson Christopher D. , Appadoo Dominique R. T. , McNaughton Don
Published: August 2012

The high-resolution (0.001 cm−1) spectrum of thiirane has been recorded at the far-infrared beamline at the Australian synchrotron between 760‑400 cm−1 and 170‑10 cm−1. Ro-vibrational transitions of the highly Coriolis coupled ν5 (628.1 cm−1) and ν15 (669.7 cm−1) fundamentals, as well as pure rotational far-IR transitions have been assigned, and rotational, centrifugal distortion, and Coriolis interaction parameters determined. ν15 gains the vast majority of its intensity from an interesting Coriolis intensity stealing mechanism, which is also outlined.
Single-molecule stochastic times in a reversible bimolecular reaction
Authors: Keller Peter , Valleriani Angelo
Published: August 2012

In this work, we consider the reversible reaction between reactants of species A and B to form the product C. We consider this reaction as a prototype of many pseudobiomolecular reactions in biology, such as for instance molecular motors. We derive the exact probability density for the stochastic waiting time that a molecule of species A needs until the reaction with a molecule of species B takes place. We perform this computation taking fully into account the stochastic fluctuations in the number of molecules of species B. We show that at low numbers of participating molecules, the exact probability density differs from the exponential density derived by assuming the law of mass action. Finally, we discuss the condition of detailed balance in the exact stochastic and in the approximate treatment.
Spectroscopic observation of simultaneous bi-directional reconnection outflows in a laboratory plasma
Authors: Brown M. R. , Cothran C. D. , Gray T. , Myers C. E. , Belova E. V.
Published: August 2012

We report a precise, direct spectroscopic measurement of simultaneous bi-directional outflows from a reconnection event in a laboratory plasma. Outflow speeds are as Alfvénic and Abel analysis shows that the outflows are generated in the plasma core. A Sweet-Parker like analysis of outflow speed coupled with external measurements of reconnection electric field and assumption of Spitzer resistivity predict an aspect ratio of the reconnection layer and reconnection rate that are close to that measured in the experiment and in simulations. However, this analysis underestimates the absolute scale of the layer, indicating other than 2D resistive physics is at play.
Improving the signal-to-noise ratio of high-speed contact mode atomic force microscopy
Authors: Payton O. D. , Picco L. , Miles M. J. , Homer M. E. , Champneys A. R.
Published: August 2012

During high-speed contact mode atomic force microscopy, higher eigenmode flexural oscillations of the cantilever have been identified as the main source of noise in the resultant topography images. We show that by selectively filtering out the frequencies corresponding to these oscillations in the time domain prior to transforming the data into the spatial domain, significant improvements in image quality can be achieved.
Effect of superbanana diffusion on fusion reactivity in stellarators
Authors: Hinton Fred L.
Published: August 2012

Fusion reactivity is usually obtained using a Maxwellian distribution. However, energy-dependent radial diffusion can modify the energy distribution. Superbanana diffusion is energy-dependent and occurs in nonaxisymmetric magnetic confinement devices, such as stellarators, because of ripple-trapped particles which can take large steps between collisions. In this paper, the D-T fusion reactivity is calculated using a non-Maxwellian energy distribution obtained by solving the Fokker-Planck equation numerically, including radial superbanana diffusion as well as energy scattering. The ions in the tail of the distribution, with energies larger than thermal, which are most needed for fusion, are depleted by superbanana diffusion. In this paper, it is shown that the D-T fusion reactivity is reduced by tail ion depletion due to superbanana diffusion, by roughly a factor of 0.5 for the parameters used in the calculation.
Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment
Authors: Takahashi Kazunori
Published: August 2012

A radiofrequency (rf) antenna for helicon plasma thruster experiments is developed and tested using a permanent magnets helicon plasma source immersed in a vacuum chamber. A magnetic nozzle is provided by permanent magnets arrays and an argon plasma is produced by a 13.56 MHz radiofrequency helicon-wave or inductively-coupled discharge. A parasitic discharge outside the source tube is successfully suppressed by covering the rf antenna with a ceramic ring and a grounded shield; a decrease in the ion saturation current of a Langmuir probe located outside the source tube is observed and the ion saturation current on axis increases simultaneously, compared with the case of a standard uncovered rf antenna. It is also demonstrated that the covered antenna can yield stable operation of the source.
Acoustic waves switch based on meta-fluid phononic crystals
Authors: Zhu Xue-Feng
Published: August 2012

The acoustic waves switch based on meta-fluid phononic crystals (MEFL PCs) is theoretically investigated. The MEFL PCs consist of fluid matrix and fluid-like inclusions with extremely anisotropic-density. The dispersion relations are calculated via the plane wave expansion method, which are in good agreement with the transmitted sound pressure level spectra obtained by the finite element method. The results show that the width of absolute band gap in MEFL PCs depends sensitively upon the orientation of the extremely anisotropic-density inclusions and reaches maximum at the rotating angle of 45°, with the gap position nearly unchanged. Also, the inter-mode conversion inside anisotropic-density inclusions can be ignored due to large acoustic mismatch. The study gives a possibility to realize greater flexibility and stronger effects in tuning the acoustic band gaps, which is very significant in the enhanced control over sound waves and has potential applications in ultrasonic imaging and therapy.
Integer quantum Hall effect in a lattice model revisited: Kubo formalism
Authors: Dutta Paramita , Maiti Santanu K. , Karmakar S. N.
Published: August 2012

We investigate numerically the integer quantum Hall effect (IQHE) in a two-dimensional square lattice with non-interacting electrons in presence of disorder and subjected to uniform magnetic field in a direction perpendicular to the lattice plane. We employ nearest-neighbor tight-binding Hamiltonian to describe the system, and obtain the longitudinal and transverse conductivities using Kubo formalism. The interplay between the magnetic field and disorder is also discussed. Our analysis may be helpful in studying IQHE in any discrete lattice model.
Enhancement of thermoelectric properties of CoSb3-based skutterudites by double filling of Tl and In
Authors: Harnwunggmoung Adul , Kurosaki Ken , Kosuga Atsuko , Ishimaru Manabu , Plirdpring Theerayuth , Yimnirun Rattikorn , Jutimoosik Jaru , Rujirawat Saroj , Ohishi Yuji , Muta Hiroaki , Yamanaka Shinsuke
Published: August 2012

Thermoelectric (TE) generators can directly generate electrical power from waste heat, and thus could be an important part of the solution to future power supply and sustainable energy management. The main obstacle to the widespread use of TE materials in diverse industries, e.g., for exhaust heat recovery in automobiles, is their low efficiency in converting heat to electricity. The conversion efficiency of TE materials is quantified by the dimensionless figure of merit, ZT, and the way to enhance ZT is to decrease the lattice thermal conductivity (κlat) of the material, while maintaining a high electrical conductivity, i.e., to create a situation in which phonons are scattered but electrons are unaffected. Here, we report skutterudites filled by Tl and In, Tl0.1InxCo4Sb12, which allow a dramatic reduction of κlat, yielding a ZT of 1.2 at 700 K. We demonstrate that the reduction of κlat is due to the effective phonon scattering induced both by the rattling of Tl and In and by the naturally formed In2O3 nanoparticles (<50 nm). The combined approach of double filling and self-formed nanostructures might be applicable to various clathrate compounds. Thus, our results point to a new strategy in the improvement of bulk TE materials.
Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions
Authors: Lai Yu-Ren , Yu Kai-Fu , Lin Yong-Han , Wu Jong-Ching , Lin Juhn-Jong
Published: August 2012

Micrometer-sized Al/AlOx/Y tunnel junctions were fabricated by the electron-beam lithography technique. The thin (≈ 1.5–2 nm thickness) insulating AlOx layer was grown on top of the Al base electrode by O2 glow discharge. The zero-bias conductances G(T) and the current-voltage characteristics of the junctions were measured in a wide temperature range 1.5–300 K. In addition to the direct tunneling conduction mechanism observed in low-G junctions, high-G junctions reveal a distinct charge transport process which manifests the thermally fluctuation-induced tunneling conduction (FITC) through short nanoconstrictions. We ascribe the experimental realization of the FITC mechanism to originating from the formations of “hot spots” (incomplete pinholes) in the AlOx layer owing to large junction-barrier interfacial roughness.
Probing near-normally propagating bulk acoustic waves using pseudo-reflection geometry Brillouin spectroscopy
Authors: Parsons L. C. , Andrews G. T.
Published: August 2012

Pseudo-reflection geometry Brillouin spectroscopy can be used to probe acoustic wave dispersion approximately along the surface normal of a material system while avoiding the difficulties associated with specularly reflected light encountered in an ideal reflection configuration. As an example of its application, we show analytically that it can be used to determine both the refractive index and bulk acoustic mode velocities of optically-isotropic non-metallic materials and confirm the utility of the approach via a series of experiments on fused quartz, gallium phosphide, water, and porous silicon films.
The nanoanatomical basis of sexual dimorphism in iridescent butterfly colouration
Authors: White Thomas E. , Macedonia Joseph , Birch Debra , Dawes Judith , Kemp Darrell J.
Published: August 2012

Structurally generated colours are at least as commonplace and varied components of animal signals as pigment colours, yet we know far less about the former, both in terms of the patterns and phenotypic variation and of their underlying correlates and causes. Many butterflies exhibit bright and iridescent colour signals that arise from a characteristic ‘ridge-lamellar’ scale surface nanoarchitecture. Although there are multiple axes of functional variation in these traits, few have been investigated. Here we present evidence that sexual dimorphism in the expression of a sexually homologous ridge-lamellar trait (iridescent ultraviolet) is mediated by sex differences in the density of lamellar-bearing scale ridges. This trait – ridge density – has also been causally related to iridescent signal variation in other coliadines (e.g. C. eurytheme), which suggests that it may offer a common basis to both intra- and intersexual differences in ultraviolet wing reflectance among these butterflies.
The transcription of interpreting data
Authors: Niemants Natacha S.A.
Published: August 2012

The growing interest in studies based on samples of authentic interpreting data goes hand in hand with the need to think of adequate methodologies to make such data available for research. During the 1980s, transcription issues posed a series of theoretical questions which may now be worth revisiting in the light of recent debates in Interpreting Studies (IS), and of new methodological instruments. Building on the premise that nothing is as practical as good theory, this paper aims at informing decisions on transcribing interpreting events. It first reviews some general theoretical issues involved in any transcription of oral data, and then engages with issues that are particular to IS.
Mediation through personal pronoun shifts in dialogue interpreting of political meetings
Authors: Zhan Cheng
Published: August 2012

This paper examines the mediation role of government staff interpreters in China. Based on data collected from six political meetings involving senior officials of Guangdong Province, with interpreting performed by staff interpreters in the Protocol Department of the Foreign Affairs Office of the People’s Government of Guangdong, the paper analyzes cases of personal pronoun shifts in the rendition of the interpreters. Results show that personal pronoun shifts occur in all of the interpreted dialogues, and can be divided into: (1) personal pronoun shifts with the same footing, including shifts between first person and third person pronouns and shifts between second person and third person pronouns, (2) personal pronoun shifts with a different footing, for purposes of avoiding misunderstanding or impoliteness, coping with frequent changes of speaking subjects, and correcting an error in the rendition. The paper argues that government staff interpreters of dialogues, with all the constraints posed by the political settings, do not always conform with the norms and rules, but perform a mediation role in communication.
Working conditions of community interpreters in Sweden
Authors: Norström Eva , Fioretos Ingrid , Gustafsson Kristina
Published: August 2012

The aim of this article is to describe and analyse the working conditions of interpreters and interpreting services in Sweden. An understanding of interpreters’ working conditions is a key to such factors as the management of resources, the reading and implementation of legislation, the organisation of interpreting services and the performance of interpreters in different situations. An understanding of interpreters’ working conditions is also important in understanding how multiculturalism and multilingualism are viewed on a national scale in Sweden. This review of the working conditions of interpreters is based on material from two joint research projects, which appear to indicate that interpreters as a group have much to say and often reflect on their work and working conditions. The interpreters participating in this study often demonstrated a strong commitment to professionalism. At the same time, however, many of the reflections recorded for this study were about things that undermine professionalism: bad working conditions, low pay, the feeling of being “as replaceable as potatoes”, and the feeling that the social status of interpreters is low. In analysing the consequences of working conditions we have found a tension between professionalism and deprofessionalisation. This tension has consequences for the rule of law and integration.
Structural changes during HCN channel gating defined by high affinity metal bridges
Authors: Kwan Daniel C.H. , Prole David L. , Yellen Gary
Published: August 2012

Hyperpolarization-activated cyclic nucleotide–sensitive nonselective cation (HCN) channels are activated by membrane hyperpolarization, in contrast to the vast majority of other voltage-gated channels that are activated by depolarization. The structural basis for this unique characteristic of HCN channels is unknown. Interactions between the S4–S5 linker and post-S6/C-linker region have been implicated previously in the gating mechanism of HCN channels. We therefore introduced pairs of cysteines into these regions within the sea urchin HCN channel and performed a Cd2+-bridging scan to resolve their spatial relationship. We show that high affinity metal bridges between the S4–S5 linker and post-S6/C-linker region can induce either a lock-open or lock-closed phenotype, depending on the position of the bridged cysteine pair. This suggests that interactions between these regions can occur in both the open and closed states, and that these regions move relative to each other during gating. Concatenated constructs reveal that interactions of the S4–S5 linker and post-S6/C-linker can occur between neighboring subunits. A structural model based on these interactions suggests a mechanism for HCN channel gating. We propose that during voltage-dependent activation the voltage sensors, together with the S4–S5 linkers, drive movement of the lower ends of the S5 helices around the central axis of the channel. This facilitates a movement of the pore-lining S6 helices, which results in opening of the channel. This mechanism may underlie the unique voltage dependence of HCN channel gating.
The contribution of hydrophobic residues in the pore-forming region of the ryanodine receptor channel to block by large tetraalkylammonium cations and Shaker B inactivation peptides
Authors: Mason Sammy A. , Viero Cedric , Euden Joanne , Bannister Mark , West Duncan , Chen S.R. Wayne , Williams Alan J.
Published: August 2012

Although no high-resolution structural information is available for the ryanodine receptor (RyR) channel pore-forming region (PFR), molecular modeling has revealed broad structural similarities between this region and the equivalent region of K+ channels. This study predicts that, as is the case in K+ channels, RyR has a cytosolic vestibule lined with predominantly hydrophobic residues of transmembrane helices (TM10). In K+ channels, this vestibule is the binding site for blocking tetraalkylammonium (TAA) cations and Shaker B inactivation peptides (ShBPs), which are stabilized by hydrophobic interactions involving specific residues of the lining helices. We have tested the hypothesis that the cytosolic vestibule of RyR fulfils a similar role and that TAAs and ShBPs are stabilized by hydrophobic interactions with residues of TM10. Both TAAs and ShBPs block RyR from the cytosolic side of the channel. By varying the composition of TAAs and ShBPs, we demonstrate that the affinity of both species is determined by their hydrophobicity, with variations reflecting alterations in the dissociation rate of the bound blockers. We investigated the role of TM10 residues of RyR by monitoring block by TAAs and ShBPs in channels in which the hydrophobicity of individual TM10 residues was lowered by alanine substitution. Although substitutions changed the kinetics of TAA interaction, they produced no significant changes in ShBP kinetics, indicating the absence of specific hydrophobic sites of interactions between RyR and these peptides. Our investigations (a) provide significant new information on both the mechanisms and structural components of the RyR PFR involved in block by TAAs and ShBPs, (b) highlight important differences in the mechanisms and structures determining TAA and ShBP block in RyR and K+ channels, and (c) demonstrate that although the PFRs of these channels contain analogous structural components, significant differences in structure determine the distinct ion-handling properties of the two species of channel.
On the incompressible limit problems for multicomponent reactive flows
Authors: Kwon Young-Sam , Trivisa Konstantina
Published: August 2012

Multicomponent reactive flows are associated with a variety of phenomena and processes: pollutant formation, biotechnology, fuel droplets in combustion, sprays, astrophysical plasma. Analyzing the physical regimes associated with various processes unfolds complex chemistry mechanisms and detailed transport phenomena. Many interesting problems in that context involve the behavior of solutions to the governing equations for multicomponent reactive flows as certain parameters vanish or become infinity. This work establishes rigorously the incompressible limit for weak solutions to multicomponent reactive flows. The analysis treats the cases of both bounded and unbounded domains.
Are there geniuses among the apes?
Authors: Herrmann Esther , Call Josep
Published: August 2012

We are often asked whether some apes are smarter than others. Here we used two individual-based datasets on cognitive abilities to answer this question and to elucidate the structure of individual differences. We identified some individuals who consistently scored well across multiple tasks, and even one individual who could be classified as exceptional when compared with her conspecifics. However, we found no general intelligence factor. Instead, we detected some clusters of certain abilities, including inferences, learning and perhaps a tool-use and quantities cluster. Thus, apes in general and chimpanzees in particular present a pattern characterized by the existence of some smart animals but no evidence of a general intelligence factor. This conclusion contrasts with previous studies that have found evidence of agfactor in primates. However, those studies have used group-based as opposed to the individual-based data used here, which means that the two sets of analyses are not directly comparable. We advocate an approach based on testing multiple individuals (of multiple species) on multiple tasks that capture cognitive, motivational and temperament factors affecting performance. One of the advantages of this approach is that it may contribute to reconcile the general and domain-specific views on primate intelligence.
Core systems of geometry in animal minds
Authors: Spelke Elizabeth S. , Lee Sang Ah
Published: August 2012

Research on humans from birth to maturity converges with research on diverse animals to reveal foundational cognitive systems in human and animal minds. The present article focuses on two such systems of geometry. One system represents places in the navigable environment by recording the distance and direction of the navigator from surrounding, extended surfaces. The other system represents objects by detecting the shapes of small-scale forms. These two systems show common signatures across animals, suggesting that they evolved in distant ancestral species. As children master symbolic systems such as maps and language, they come productively to combine representations from the two core systems of geometry in uniquely human ways; these combinations may give rise to abstract geometric intuitions. Studies of the ontogenetic and phylogenetic sources of abstract geometry therefore are illuminating of both human and animal cognition. Research on animals brings simpler model systems and richer empirical methods to bear on the analysis of abstract concepts in human minds. In return, research on humans, relating core cognitive capacities to symbolic abilities, sheds light on the content of representations in animal minds.
Modularity, comparative cognition and human uniqueness
Authors: Shettleworth Sara J.
Published: August 2012

Darwin's claim ‘that the difference in mind between man and the higher animals … is certainly one of degree and not of kind’ is at the core of the comparative study of cognition. Recent research provides unprecedented support for Darwin's claim as well as new reasons to question it, stimulating new theories of human cognitive uniqueness. This article compares and evaluates approaches to such theories. Some prominent theories propose sweeping domain-general characterizations of the difference in cognitive capabilities and/or mechanisms between adult humans and other animals. Dual-process theories for some cognitive domains propose that adult human cognition shares simple basic processes with that of other animals while additionally including slower-developing and more explicit uniquely human processes. These theories are consistent with a modular account of cognition and the ‘core knowledge’ account of children's cognitive development. A complementary proposal is that human infants have unique social and/or cognitive adaptations for uniquely human learning. A view of human cognitive architecture as a mosaic of unique and species-general modular and domain-general processes together with a focus on uniquely human developmental mechanisms is consistent with modern evolutionary-developmental biology and suggests new questions for comparative research.
Coevolution of learning and data-acquisition mechanisms: a model for cognitive evolution
Authors: Lotem Arnon , Halpern Joseph Y.
Published: August 2012

A fundamental and frequently overlooked aspect of animal learning is its reliance on compatibility between the learning rules used and the attentional and motivational mechanisms directing them to process the relevant data (called heredata-acquisition mechanisms). We propose that this coordinated action, which may first appear fragile and error prone, is in fact extremely powerful, and critical for understanding cognitive evolution. Using basic examples from imprinting and associative learning, we argue that by coevolving to handle the natural distribution of data in the animal's environment, learning and data-acquisition mechanisms are tuned jointly so as to facilitate effective learning using relatively little memory and computation. We then suggest that this coevolutionary process offers a feasible path for the incremental evolution of complex cognitive systems, because it can greatly simplify learning. This is illustrated by considering how animals and humans can use these simple mechanisms to learn complex patterns and represent them in the brain. We conclude with some predictions and suggested directions for experimental and theoretical work.
Individual variation in cognitive performance: developmental and evolutionary perspectives
Authors: Thornton Alex , Lukas Dieter
Published: August 2012

Animal cognition experiments frequently reveal striking individual variation but rarely consider its causes and largely ignore its potential consequences. Studies often focus on a subset of high-performing subjects, sometimes viewing evidence from a single individual as sufficient to demonstrate the cognitive capacity of a species. We argue that the emphasis on demonstrating species-level cognitive capacities detracts from the value of individual variation in understanding cognitive development and evolution. We consider developmental and evolutionary interpretations of individual variation and use meta-analyses of data from published studies to examine predictors of individual performance. We show that reliance on small sample sizes precludes robust conclusions about individual abilities as well as inter- and intraspecific differences. We advocate standardization of experimental protocols and pooling of data between laboratories to improve statistical rigour. Our analyses show that cognitive performance is influenced by age, sex, rearing conditions and previous experience. These effects limit the validity of comparative analyses unless developmental histories are taken into account, and complicate attempts to understand how cognitive traits are expressed and selected under natural conditions. Further understanding of cognitive evolution requires efforts to elucidate the heritability of cognitive traits and establish whether elevated cognitive performance confers fitness advantages in nature.
What is comparable in comparative cognition?
Authors: Chittka Lars , Rossiter Stephen J. , Skorupski Peter , Fernando Chrisantha
Published: August 2012

To understand how complex, or ‘advanced’ various forms of cognition are, and to compare them between species for evolutionary studies, we need to understand the diversity of neural–computational mechanisms that may be involved, and to identify the genetic changes that are necessary to mediate changes in cognitive functions. The same overt cognitive capacity might be mediated by entirely different neural circuitries in different species, with a many-to-one mapping between behavioural routines, computations and their neural implementations. Comparative behavioural research needs to be complemented with a bottom-up approach in which neurobiological and molecular-genetic analyses allow pinpointing of underlying neural and genetic bases that constrain cognitive variation. Often, only very minor differences in circuitry might be needed to generate major shifts in cognitive functions and the possibility that cognitive traits arise by convergence or parallel evolution needs to be taken seriously. Hereditary variation in cognitive traits between individuals of a species might be extensive, and selection experiments on cognitive traits might be a useful avenue to explore how rapidly changes in cognitive abilities occur in the face of pertinent selection pressures.
Simple minds: a qualified defence of associative learning
Authors: Heyes Cecilia
Published: August 2012

Using cooperation in chimpanzees as a case study, this article argues that research on animal minds needs to steer a course between ‘association-blindness’—the failure to consider associative learning as a candidate explanation for complex behaviour—and ‘simple-mindedness’—the assumption that associative explanations trump more cognitive hypotheses. Association-blindness is challenged by the evidence that associative learning occurs in a wide range of taxa and functional contexts, and is a major force guiding the development of complex human behaviour. Furthermore, contrary to a common view, association-blindness is not entailed by the rejection of behaviourism. Simple-mindedness is founded on Morgan's canon, a methodological principle recommending ‘lower’ over ‘higher’ explanations for animal behaviour. Studies in the history and philosophy of science show that Morgan failed to offer an adequate justification for his canon, and subsequent attempts to justify the canon using evolutionary arguments and appeals to simplicity have not been successful. The weaknesses of association-blindness and simple-mindedness imply that there are no short-cuts to finding out about animal minds. To decide between associative and yet more cognitive explanations for animal behaviour, we have to spell them out in sufficient detail to allow differential predictions, and to test these predictions through observation and experiment.
Cognition in insects
Authors: Webb Barbara
Published: August 2012

A traditional view of cognition is that it involves an internal process that represents, tracks or predicts an external process. This is not a general characteristic of all complex neural processing or feedback control, but rather implies specific forms of processing giving rise to specific behavioural capabilities. In this paper, I will review the evidence for such capabilities in insect navigation and learning. Do insects know where they are, or do they only know what to do? Do they learn what stimuli mean, or do they only learn how to behave?
Associative learning and animal cognition
Authors: Dickinson Anthony
Published: August 2012

Associative learning plays a variety of roles in the study of animal cognition from a core theoretical component to a null hypothesis against which the contribution of cognitive processes is assessed. Two developments in contemporary associative learning have enhanced its relevance to animal cognition. The first concerns the role of associatively activated representations, whereas the second is the development of hybrid theories in which learning is determined by prediction errors, both directly and indirectly through associability processes. However, it remains unclear whether these developments allow associative theory to capture the psychological rationality of cognition. I argue that embodying associative processes within specific processing architectures provides mechanisms that can mediate psychological rationality and illustrate such embodiment by discussing the relationship between practical reasoning and the associative-cybernetic model of goal-directed action.
Biological and artificial cognition: what can we learn about mechanisms by modelling physical cognition problems using artificial intelligence planning techniques?
Authors: Chappell Jackie , Hawes Nick
Published: August 2012

Do we fully understand the structure of the problems we present to our subjects in experiments on animal cognition, and the information required to solve them? While we currently have a good understanding of the behavioural and neurobiological mechanisms underlying associative learning processes, we understand much less about the mechanisms underlying more complex forms of cognition in animals. In this study, we present a proposal for a new way of thinking about animal cognition experiments. We describe a process in which a physical cognition task domain can be decomposed into its component parts, and models constructed to represent both the causal events of the domain and the information available to the agent. We then implement a simple set of models, using the planning language MAPL within the MAPSIM simulation environment, and applying it to a puzzle tube task previously presented to orangutans. We discuss the results of the models and compare them with the results from the experiments with orangutans, describing the advantages of this approach, and the ways in which it could be extended.
Differences in insulin resistance markers between children born small for gestational age or born preterm appropriate for gestational age
Authors: Kistner Anna , Rakow Alexander , Legnevall Lena , Marchini Giovanna , Brismar Kerstin , Hall Kerstin , Vanpée Mireille
Published: August 2012

Aim:  To evaluate the impact of prenatal or postnatal compromised environment on glucose homoeostasis in children born preterm and appropriate for gestational age or small for gestational age (SGA) at term.

Method:  Seventy‐seven children (median 9.9 years, range 8.5–10) born at Karolinska Hospital were allocated to three groups: 21 subjects born before 30 weeks of gestational age (preterm), 26 SGA at term and 30 at term with appropriate birth weight (control). Anthropometric measurements were taken, and fasting blood samples for haemoglobin A1c, glucose, insulin, IGFBP‐1, IGF‐1 and lipid profile were taken. Glucose, insulin and IGFBP‐1 samples were taken at 0, 30 and 120 min during an oral glucose tolerance test (OGTT).

Results:  Subjects born preterm or SGA were shorter and thinner compared with Controls. After adjustment for body mass index (BMI), the SGA group had higher basal insulin levels (p = 0.029), higher homoeostasis model assessment—insulin resistance (p = 0.012) and lower whole‐body insulin sensitivity index (p = 0.007) than Controls. IGFBP‐1 decrease during OGTT was attenuated in the Preterm group compared with the Control (p = 0.045) and SGA groups (p = 0.007).

Conclusion:  The higher fasting insulin level in the SGA children, adjusted for BMI, could indicate peripheral insulin resistance. Preterm born children had reduced suppression of IGFBP‐1 during OGTT, suggesting hepatic insulin resistance.
Buccal and lingual bone level alterations after immediate implantation of four implant surfaces: a study in dogs
Authors: Bonfante Estevam A. , Janal Malvin N. , Granato Rodrigo , Marin Charles , Suzuki Marcelo , Tovar Nick , Coelho Paulo G.
Published: August 2012

Objectives

Bone formation and maintenance around implants placed immediately after tooth extraction may be affected by implant surface treatment and compromise long‐term esthetic results. This study morphometrically evaluated buccal bone loss and bone‐to‐implant contact (BIC) of four implant systems placed immediately after tooth extraction in a dog model.

Material and Methods

The premolars of eight beagle dogs were bilaterally extracted with a full‐thickness flap, and root‐form dental implants were placed on the root extraction socket. Implants (n = 16 each) with different surface treatments were placed from sites 1 to 4 and alternated between animals to allow evaluation of the same number of implants at sites and evaluation time points. Implant surface treatments were as follows: anodized, discrete crystalline deposition, SLActive, and microblasted. The left and right side provided implants that stayed for 2 and 4 weeks, respectively. Submerged healing was allowed and bone‐to‐implant contact (BIC) and buccal bone loss were morphometrically measured. Linear mixed models (P < 0.05) were used to assess differences between groups, across time, and their interaction.

Results

Buccal bone loss was observed to approximately double between 2 and 4 weeks (P = 0.01). BIC also increased between 2 and 4 weeks, by 20–25% (P = 0.01). These changes were statistically similar for each surface.

Conclusion

When placed immediately after tooth extraction, the evaluated histomorphometric parameters vary only with time.
Screening for depression and diabetes‐related distress in a diabetes outpatient clinic
Authors: Fleer J. , Tovote K. A. , Keers J. C. , Links T. P. , Sanderman R. , Coyne J. C. , Schroevers M. J.
Published: August 2012

Aims  To investigate: (1) the willingness of patients with diabetes to participate in a screening programme; (2) the extent to which patients with diabetes who screen positive endorse need for psychosocial care; (3) the rate of referral to psychosocial care during screening vs. usual care.

Methods  Four hundred and ninety‐nine patients with diabetes were invited to complete the Center for Epidemiologic Studies Depression and the Problem Areas in Diabetes questionnaires. Patients screening positive on either instrument were invited for an interview. One year after screening was withdrawn, rates of referral to psychosocial care were assessed from physician reports of patient referrals.

Results  In total, 349/499 (70%) patients with diabetes completed the questionnaire. Patients who did not take up the screening were younger, smoked more often and had higher HbA1c values. ‘No‐shows’ for clinical appointments accounted for 74% of non‐participation. Of the 104 (30% of 349) patients screening positive, 45 accepted an invitation for an interview. Finally, 36/104 (35%) would like a referral for psychological care. Seven per cent of patients were referred to psychological care during screening compared with 1% when screening was withdrawn.

Conclusions  Results raise questions as to whether screening is the most efficient way to identify patients with psychological problems. Many patients did not take up the screening, especially those with low adherence to diabetes care in general. Furthermore, few patients screening positive wanted to be referred. Screening should be evaluated in the context of consideration of alternative ways to identify at‐risk patients, including providing resources to deal with patients with already known adjustment and adherence problems.