On domain walls in a Ginzburg-Landau non-linear S^2-sigma model

The domain wall solutions of a Ginzburg-Landau non-linear $S^2$-sigma hybrid model are unveiled. There are three types of basic topological walls and two types of degenerate families of composite - one topological, the other non-topological- walls. The domain wall solutions are identified as the finite action trajectories (in infinite time) of a related mechanical system that is Hamilton-Jacobi separable in sphero-conical coordinates. The physical and mathematical features of these domain walls are thoroughly discussed.Comment: 26 pages, 18 figure

The response of taxonomic and functional diversity of the seed bank to agricultural intensification and soil properties in two Mediterranean cereal areas

Weed seed bank diversity has been severely impacted by agriculture intensifi cation. However, the functional consequences have been poorly studied in highly intensifi ed agro-ecosystems.Postprint (published version

FRW Universe in Ho\~rava Gravity

Recently, a field theoretic model for a UV complete theory of gravity has been proposed by Ho\~{r}ava. This theory is a non-relativistic renormalizable gravity theory which coincides with Einstein's general relativity at large distances. Subsequently L\"{u} et al have formulated the modified Friedmann equations and have presented a solution in vacuum. In the present work, we rewrite the modified FRW equations in the form of usual FRW equations in Einstein gravity and consequences has been analyzed. Also the thermodynamics of the FRW universe has been studied

La geografía de Madrid en Internet. Recursos para la investigación y la docencia

Sin resume

Supersymmetric spacetimes in 2+1 adS-supergravity models

We find a class of (2+1)-dimensional spacetimes admitting Killing spinors appropriate to (2,0) adS-supergravity. The vacuum spacetimes include anti-de Sitter (adS) space and charged extreme black holes, but there are many others, including spacetimes of arbitrarily large negative energy that have only conical singularities, and the spacetimes of fractionally charged point particles. The non-vacuum spacetimes are those of self-gravitating solitons obtained by coupling (2,0) adS supergravity to sigma-model matter. We show, subject to a condition on the matter currents (satisfied by the sigma model), and a conjecture concerning global obstructions to the existence of certain types of spinor fields, that the mass of each supersymmetric spacetime saturates a classical bound, in terms of the angular momentum and charge, on the total energy of arbitrary field configurations with the same boundary conditions, although these bounds may be violated quantum mechanically.Comment: 47 pages, phyzzx.tex, no figures

Holons Visual Representation for Image Retrieval

This work was supported in part by the National Natural Science Foundation of China under Grant 61370149, in part by the Fundamental Research Funds for the Central Universities under Grant ZYGX2013J083, by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry under Grant LXHG42DL, by the National Basic Research Program of China under Grant 2013CB329305, by the National Natural Science Foundation of China under Grant 61422213, and by the Strategic Priority Research Program of the Chinese Academy of Sciences

Optically-enhanced performance of polymer solar cells with low concentration of gold nanorods in the anodic buffer layer

In this work, the effect of gold nanorods on the performance of poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric-acid-methyl-ester bulk heterojunction solar cells was investigated. Gold nanorods were introduced into the anodic buffer layer by simply blending them with the solution of poly(3,4-ethyl enedioxythiophene):poly(styrenesulfonate). Even with a fairly low density of the nanorods, the resulting devices showed a remarkable 21.3% enhancement in the power conversion efficiency and a 13% enlargement in the short circuit current. By examining the absorbance profiles of active films made with different conditions,\ud such enhancements can be related to the localized transverse and longitudinal plasmon resonance modes in the metallic nanoparticles. Gold nanorods helped as well in reducing the device series resistance by up to 36%, which also contributed to the global enhancement in the efficiency

(2,0) Chern-Simons Supergravity Plus Matter Near the Boundary of AdS_3

We examine the boundary behaviour of the gauged N=(2,0) supergravity in D=3 coupled to an arbitrary number of scalar supermultiplets which parametrize a Kahler manifold. In addition to the gravitational coupling constant, the model depends on two parameters, namely the cosmological constant and the size of the Kahler manifold. It is shown that regular and irregular boundary conditions can be imposed on the matter fields depending on the size of the sigma model manifold. It is also shown that the super AdS transformations in the bulk produce the transformations of the N=(2,0) conformal supergravity and scalar multiplets on the boundary, containing fields with nonvanishing Weyl weights determined by the ratio of the sigma model and the gravitational coupling constants. Various types of (2,0) superconformal multiplets are found on the boundary and in one case the superconformal symmetry is shown to be realized in an unconventional way.Comment: 28 pages, latex, references adde

Cognitive Principles of Schematisation for Wayfinding Assistance

People often need assistance to successfully perform wayfinding tasks in unfamiliar environments. Nowadays, a huge variety of wayfinding assistance systems exists. All these systems intend to present the needed information for a certain wayfinding situation in an adequate presentation. Some wayfinding assistance systems utilize findings for the field of cognitive sciences to develop and design cognitive ergonomic approaches. These approaches aim to be systems with which the users can effortless interact with and which present needed information in a way the user can acquire the information naturally. Therefore it is necessary to determinate the information needs of the user in a certain wayfinding task and to investigate how this information is processed and conceptualised by the wayfinder to be able to present it adequately. Cognitive motivated schematic maps are an example which employ this knowledge and emphasise relevant information and present it in an easily readable way. In my thesis I present a transfer approach to reuse the knowledge of well-grounded knowledge of schematisation techniques from one externalisation such as maps to another externalization such as virtual environments. A analysis of the informational need of the specific wayfinding task route following is done one the hand of a functional decomposition as well as a deep analysis of representation-theoretic consideration of the external representations maps and virtual environments. Concluding from these results, guidelines for transferring schematisation principles between different representation types are proposed. Specifically, this thesis chose the exemplary transfer of the schematisation technique wayfinding choremes from a map presentation into a virtual environment to present the theoretic requirements for a successful transfer. Wayfinding choremes are abstract mental concepts of turning action which are accessible as graphical externalisation integrated into route maps. These wayfinding choremes maps emphasis the turning action along the route by displaying the angular information as prototypes of 45° or 90°. This schematisation technique enhances wayfinding performance by supporting the matching processes between the map representation and the internal mental representation of the user. I embed the concept of wayfinding choremes into a virtual environment and present a study to test if the transferred schematisation technique also enhance the wayfinding performance. The empirical investigations present a successful transfer of the concept of the wayfinding choremes. Depending on the complexity of the route the embedded schematization enhance the wayfinding performance of participants who try to follow a route from memory. Participants who trained and recall the route in a schematised virtual environment make fewer errors than the participants of the unmodified virtual world. This thesis sets an example of the close research circle of cognitive behavioural studies to representation-theoretical considerations to applications of wayfinding assistance and their evaluations back to new conclusions in cognitive science. It contributes an interdisciplinary comprehensive inspection of the interplay of environmental factors and mental processes on the example of angular information and mental distortion of this information

Gold nanorods on the cathode electrode for enhancing the efficiency of polymer solar cells

Different densities of gold nanorods (GNRs) were incorporated on the back electrode of bulk heterojunction organic solar cell (OSC). GNRs layers (1, 3, and 5) were deposited on top of the poly(3-hexylthiophene) (P3HT) and phenyl- C61-butyric acid methyl ester (PCBM) layer using spin-casting technique. According to the optical and structural characterizations, the solar cell devices incorporated with one layer of gold nanorods showed an enhancement in both power conversion efficiency and short-circuit current by up to 14% and 22% respectively as compared to the devices without gold nanorods. This result suggests that GNRs in the back electrode of polymer solar cells act as backscattering elements. They not only increase the optical path length in the active layer but also store energy in localized surface plasmon resonance mode. Both mechanisms lead to enhancement of light absorption and in turn contribute to photocurrent generation and the overall power conversion efficiency. On the other hand, the solar cells with high density GNRs on the back electrode showed inferior performance compared to that of low density integrated ones. The decrease in PCE would stem from enhanced charge recombination induced by high density GNRs. Furthermore, generation of intense local electric fields named hotspots, would reduce the charge transportation and exciton dissociation probability. In such cases, the power conversion efficiency of the device is observed to be less than that for one layer GNRs or even the control device