A Potts Neuron Approach to Communication Routing

A feedback neural network approach to communication routing problems is developed with emphasis on Multiple Shortest Path problems, with several requests for transmissions between distinct start- and endnodes. The basic ingredients are a set of Potts neurons for each request, with interactions designed to minimize path lengths and to prevent overloading of network arcs. The topological nature of the problem is conveniently handled using a propagator matrix approach. Although the constraints are global, the algorithmic steps are based entirely on local information, facilitating distributed implementations. In the polynomially solvable single-request case the approach reduces to a fuzzy version of the Bellman-Ford algorithm. The approach is evaluated for synthetic problems of varying sizes and load levels, by comparing with exact solutions from a branch-and-bound method. With very few exceptions, the Potts approach gives legal solutions of very high quality. The computational demand scales merely as the product of the numbers of requests, nodes, and arcs.Comment: 10 pages LaTe

Soil carbon stock increases in the organic layer of boreal middle-aged stands

Changes in the soil carbon stock can potentially have a large influence on global carbon balance between terrestrial ecosystems and atmosphere. Since carbon sequestration of forest soils is influenced by human activities, reporting of the soil carbon pool is a compulsory part of the national greenhouse gas (GHG) inventories. Various soil carbon models are applied in GHG inventories, however, the verification of model-based estimates is lacking. In general, the soil carbon models predict accumulation of soil carbon in the middle-aged stands, which is in good agreement with chronosequence studies and flux measurements of eddy sites, but they have not been widely tested with repeated measurements of permanent plots. The objective of this study was to evaluate soil carbon changes in the organic layer of boreal middle-aged forest stands. Soil carbon changes on re-measured sites were analyzed by using soil survey data that was based on composite samples as a first measurement and by taking into account spatial variation on the basis of the second measurement. By utilizing earlier soil surveys, a long sampling interval, which helps detection of slow changes, could be readily available. <br><br> The range of measured change in the soil organic layer varied from −260 to 1260 g m<sup>−2</sup> over the study period of 16–19 years and 23 ± 2 g m<sup>−2</sup> per year, on average. The increase was significant in 6 out of the 38 plots from which data were available. Although the soil carbon change was difficult to detect at the plot scale, the overall increase measured across the middle-aged stands agrees with predictions of the commonly applied soil models. Further verification of the soil models is needed with larger datasets that cover wider geographical area and represent all age classes, especially young stands with potentially large soil carbon source

Electronic-structure-induced deformations of liquid metal clusters

Ab initio molecular dynamics is used to study deformations of sodium clusters at temperatures $500\cdots 1100$ K. Open-shell Na$_{14}$ cluster has two shape isomers, prolate and oblate, in the liquid state. The deformation is stabilized by opening a gap at the Fermi level. The closed-shell Na$_8$ remains magic also at the liquid state.Comment: REVTex, 11 pages, no figures, figures (2) available upon request (e-mail to hakkinen at jyfl.jyu.fi), submitted to Phys. Rev.

Conductance through analytic constrictions

We study the dependence of the intrinsic conductance of a nanocontact on its shape by using the recursion-transfer-matrix method. Hour-glass, torus, and spherical shapes are defined through analytic potentials, the latter two serving as rough models for ring-like and spherical molecules, respectively. The sensitivity of the conductance to geometric details is analyzed and discussed. Strong resonance effects are found for a spherical contact weakly coupled to electron reservoirs.Comment: 7 pages, 12 figure

Supported magnetic nanoclusters: Softlanding of Pd clusters on a MgO surface

Low-energy deposition of neutral Pd_N clusters (N=2-7 and 13) on a MgO(001) surface F-center (FC) was studied by spin-density-functional molecular dynamics simulations. The incident clusters are steered by an attractive "funnel" created by the FC, resulting in adsorption of the cluster, with one of its atoms bonded atop of the FC. The deposited Pd_2-Pd_6 clusters retain their gas-phase structures, while for N>6 surface-commensurate isomers are energetically more favorable. Adsorbed clusters with N > 3 are found to remain magnetic at the surface.Comment: 5 pages, 2 figs, Phys.Rev.Lett., accepte

Male brain type women and female brain type men : Gender atypical cognitive profiles and their correlates

Gender differences exist in abilities, interests, and occupations. According to the Empathizing-Systemizing theory, the reason for all gender differences lies in the relative weights of two cognitive processes: women empathize more, which is useful in understanding people, while men systemize more, which means interpreting phenomena as rule-based systems. The terms "male and female brain type" refer to a heightened preference for one process over the other. We aimed to find out whether the gender atypical groups of male brain type women and female brain type men are more similar to the opposite sex than to their own in terms of a range of social, cognitive and personality variables. Female and male brain type groups were identified and compared within both genders in an online study (N = 2983). The results show there are female brain type men and male brain type women, who are characterized by qualities more often associated with the opposite sex, and who have not been reached by prior research. Thus, these findings demonstrate that cognitive type is a more powerful predictor of certain characteristics than is biological sex.Peer reviewe

Electronic structure and dimerization of a single monatomic gold wire

The electronic structure of a single monatomic gold wire is presented for the first time. It has been obtained with state-of-the-art ab-initio full-potential density-functional (DFT) LMTO (linearized muffin-tin orbital) calculations taking into account relativistic effects. For stretched structures in the experimentally accessible range the conduction band is exactly half-filled, whereas the band structures are more complex for the optimized structure. By studying the total energy as a function of unit-cell length and of a possible bond-length alternation we find that the system can lower its total energy by letting the bond lengths alternate leading to a structure containing separated dimers with bond lengths of about 2.5 \AA, largely independent of the stretching. However, first for fairly large unit cells (above roughly 7 \AA), is the total-energy gain upon this dimerization comparable with the energy costs upon stretching. We propose that this together with band-structure effects is the reason for the larger interatomic distances observed in recent experiments. We find also that although spin-orbit couplings lead to significant effects on the band structure, the overall conclusions are not altered, and that finite Au_2, Au_4, and Au_6 chains possess electronic properties very similar to those of the infinite chain.Comment: (14 pages, 5 figures; Elsevier Preprint style elsart.sty

Empathizers and systemizers process social information differently

Using the empathizing-systemizing theory as our framework, we investigated how people with high self-reported empathizing (having good social skills and being interested in people) and systemizing (being interested in physical things and processes) differ in the social information processing of emotionally negative photographs of people during “spontaneous watching” and emotional and cognitive empathy tasks. Empathizers evaluated the pictures as more emotionally touching and the reactions in the photographs more understandable than the systemizers. Compared to the empathizers, systemizers had stronger activations in the posterior cingulate cortex, an area related to cognitive empathy, as well as in the left superior temporal gyrus and middle frontal gyrus when watching emotional photographs spontaneously. During guided emotional and cognitive empathy tasks, these differences disappeared. However, during the emotional empathy task, higher systemizing was associated with weaker activation of the right inferior frontal gyrus /insula. Furthermore, during emotional and cognitive empathy tasks, empathizing was related to increased activations of the amygdala which were in turn related to higher behavioral ratings of emotional and cognitive empathy. The results suggest that empathizers and systemizers engage in social information processing differently: systemizers in more cognitive terms and empathizers with stronger automatic emotional reactions.Peer reviewe

Non-magnetic and magnetic thiolate-protected Au25 superatoms on Cu(111), Ag(111) and Au(111) surfaces

Geometry, electronic structure, and magnetic properties of methylthiolate-stabilized Au$_{25}$L$_{18}$ and MnAu$_{24}$L$_{18}$ (L = SCH$_3$) clusters adsorbed on noble-metal (111) surfaces have been investigated by using spin-polarized density functional theory computations. The interaction between the cluster and the surface is found to be mediated by charge transfer mainly from or into the ligand monolayer. The electronic properties of the 13-atom metal core remain in all cases rather undisturbed as compared to the isolated clusters in gas phase. The Au$_{25}$L$_{18}$ cluster retains a clear HOMO - LUMO energy gap in the range of 0.7 eV to 1.0 eV depending on the surface. The ligand layer is able to decouple the electronic structure of the magnetic MnAu$_{24}$L$_{18}$ cluster from Au(111) surface, retaning a high local spin moment of close to 5 $\mu_{B}$ arising from the spin-polarized Mn(3d) electrons. These computations imply that the thiolate monolayer-protected gold clusters may be used as promising building blocks with tunable energy gaps, tunneling barriers, and magnetic moments for applications in the area of electron and/or spin transport.Comment: 5 pages, 4 figures, 1 tabl