Optical response of two-dimensional few-electron concentric double quantum rings: A local-spin-density-functional theory study

We have investigated the dipole charge- and spin-density response of few-electron two-dimensional concentric nanorings as a function of the intensity of a erpendicularly applied magnetic field. We show that the dipole response displays signatures associated with the localization of electron states in the inner and outer ring favored by the perpendicularly applied magnetic field. Electron localization produces a more fragmented spectrum due to the appearance of additional edge excitations in the inner and outer ring.

Optimal network topologies for local search with congestion

The problem of searchability in decentralized complex networks is of great importance in computer science, economy, and sociology. We present a formalism that is able to cope simultaneously with the problem of search and the congestion effects that arise when parallel searches are performed, and we obtain expressions for the average search cost both in the presence and the absence of congestion. This formalism is used to obtain optimal network structures for a system using a local search algorithm. It is found that only two classes of networks can be optimal: starlike configurations, when the number of parallel searches is small, and homogeneous-isotropic configurations, when it is large.

Local size segregation in polydisperse hard sphere fluids

The structure of polydisperse hard sphere fluids, in the presence of a wall, is studied by the Rosenfeld density functional theory. Within this approach, the local excess free energy depends on only four combinations of the full set of density fields. The case of continuous polydispersity thereby becomes tractable. We predict, generically, an oscillatory size segregation close to the wall, and connect this, by a perturbation theory for narrow distributions, with the reversible work for changing the size of one particle in a monodisperse reference fluid.

Evolutionary dynamics of molecular markers during local adaptation: a case study in Drosophila subobscura

Background: Natural selection and genetic drift are major forces responsible for temporal genetic changes in populations. Furthermore, these evolutionary forces may interact with each other. Here we study the impact of an ongoing adaptive process at the molecular genetic level by analyzing the temporal genetic changes throughout 40 generations of adaptation to a common laboratory environment. Specifically, genetic variability, population differentiation and demographic structure were compared in two replicated groups of Drosophila subobscura populations recently sampled from different wild sources. Results: We found evidence for a decline in genetic variability through time, along with an increase in genetic differentiation between all populations studied. The observed decline in genetic variability was higher during the first 14 generations of laboratory adaptation. The two groups of replicated populations showed overall similarity in variability patterns. Our results also revealed changing demographic structure of the populations during laboratory evolution, with lower effective population sizes in the early phase of the adaptive process. One of the ten microsatellites analyzed showed a clearly distinct temporal pattern of allele frequency change, suggesting the occurrence of positive selection affecting the region around that particular locus. Conclusion: Genetic drift was responsible for most of the divergence and loss of variability between and within replicates, with most changes occurring during the first generations of laboratory adaptation. We also found evidence suggesting a selective sweep, despite the low number of molecular markers analyzed. Overall, there was a similarity of evolutionary dynamics at the molecular level in our laboratory populations, despite distinct genetic backgrounds and some differences in phenotypic evolution.

Water tanks as ecosystems. Local ecosystemic perception for integral management of water tanks in Tamil Nadu, South India

Water tanks offer from many centuries ago solutions in South India for several problems related with water scarcity. They are a traditional water harvesting system wide spread in this territory, allowing a potential decentralized and participatory management of the local population on their own resources. Although water tanks¿ main function is irrigation, they have many other uses, functions and natural resources associated, involving stakeholders in the villages apart from those farmers making use of the irrigation. Water tanks provide a variety of landscapes and biodiversity that creates a valuable heterogeneous territory. The complexity of such an ecosystem should be managed with an integral perspective, considering all the elements involved and their relations, and understanding that water tanks are not just water deposits. This multidisciplinary study tries to demonstrate the idea of water tanks as ecosystems, describing and analyzing deeply and in an unprecedentedly way the functions, uses, natural resources and stakeholders. The research also focuses in the assessment of the ecosystemic perception of the local population of some villages in Tamil Nadu, employing diverse anthropological methodology.

Effect of olive oil on early and late events of colon carcinogenesis in rats: modulation of arachidonic acid metabolism and local prostaglandin E2 synthesis.

BACKGROUND Animal model studies have shown that the colon tumour promoting effect of dietary fat depends not only on the amount but on its fatty acid composition. With respect to this, the effect of n9 fatty acids, present in olive oil, on colon carcinogenesis has been scarcely investigated. AIMS To assess the effect of an n9 fat diet on precancer events, carcinoma development, and changes in mucosal fatty acid composition and prostaglandin (PG)E2 formation in male Sprague-Dawley rats with azoxymethane induced colon cancer. METHODS Rats were divided into three groups to receive isocaloric diets (5% of the energy as fat) rich in n9, n3, or n6 fat, and were administered azoxymethane subcutaneously once a week for 11 weeks at a dose rate of 7.4 mg/kg body weight. Vehicle treated groups received an equal volume of normal saline. Groups of animals were colectomised at weeks 12 and 19 after the first dose of azoxymethane or saline. Mucosal fatty acids were assessed at 12 and 19 weeks. Aberrant crypt foci and the in vivo intracolonic release of PGE2 were assessed at week 12, and tumour formation at week 19. RESULTS Rats on the n6 diet were found to have colonic aberrant crypt foci and adenocarcinomas more often than those consuming either the n9 or n3 diet. There were no differences between the rats on the n9 and n3 diets. On the other hand, administration of both n9 and n3 diets was associated with a decrease in mucosal arachidonate concentrations as compared with the n6 diet. Carcinogen treatment induced an appreciable increase in PGE2 formation in rats fed the n6 diet, but not in those fed the n3 and n9 diets. CONCLUSIONS Dietary olive oil prevented the development of aberrant crypt foci and colon carcinomas in rats, suggesting that olive oil may have chemopreventive activity against colon carcinogenesis. These effects may be partly due to modulation of arachidonic acid metabolism and local PGE2synthesis.

Diagnòstic en profunditat sobre la integració dels i les joves de 14 a 18 anys migrats a Catalunya

La present recerca s’emmarca doncs, a l’eix 3 definit pel Pacte Nacional per a la Immigració (PNI), sobre la integració de la nova població catalana i de la societat d’acollida en una cultura pública comuna, mantenint la cohesió social. Entenem la integració com un procés dinàmic d’apropament i empatia recíprocs entre la persona migrada i la societat d’acollida, fet que suposa el reconeixement dels valors de cada grup en la seva diferència i en la seva igualtat per tal d’ enriquir al conjunt social. Apostem per la integració des d’un enfocament intercultural de diàleg i intercanvi, on el reconeixement de la condició de ciutadania, és indispensable i, ha de permetre tenir presents totes les dimensions de la integració: estructural, cognitiva i cultural, social i de la identitat (Martínez, 2006). Aquest repte es tradueix en la construcció de la ciutadania des de la diversitat ètnica i cultural avançant així cap a una autèntica interculturalitat. Es parteix d’un concepte d’integració bidireccional, dinàmic i continu, entre els joves migrats i la resta, coincideix totalment amb el que reconeix el PNI. La finalitat d’aquesta recerca és identificar els elements clau de l’estat actual de la integració dels joves migrats a Catalunya, per això cal definir tant els elements constitutius com els entramats del procés de la integració d’aquesta joventut al context català. La metodologia serà un estudi per enquesta, amb una mostra de 3000 joves de Catalunya. L’estudi descriptiu es complementarà amb grups de discussió de joves i entrevistes a agents socials i educatius implicats en l’acompanyament a aquests joves. Plantegem, per tant, un estudi descriptiu-comprensiu, que combina el treball sobre dades quantitatives i dades qualitatives en funció de l’objecte a valorar, sota una lògica de complementarietat (Bericat, 1998). En l’estudi per enquesta, s’aplicarà el “Qüestionari de cohesió social entre joves” elaborat per Palou (2009). Per l’aproximació qualitativa, es faran grups de discussió amb joves per analitzar en profunditat la seva realitat; i finalment, es faran entrevistes en profunditat a agents socials i educatius. El rigor metodològic permetrà que aquesta anàlisi en profunditat tingui per fruit línies clares per a elaborar propostes afavoridores per la convivència i la cohesió social.La integració a una cultura pública comuna (objectiu clau del PNI i el Pla de ciutadania i immigració 2009-2012) passa per l'Administració més propera a les persones (en aquest cas, els joves migrats i migrades del municipi), a través de les polítiques de ciutadania per a la joventut. Els resultats del present projecte pretenen orientar propostes d’actuació en aquest nivell, bé sigui en clau d’acollida i coneixement de la llengua i l’entorn com d’integració al teixit social i associatiu del barri o municipi.Més enllà de la política pública local, l’aplicabilitat del projecte que es presenta també troba un altre encaix en les polítiques educatives de Catalunya i, més concretament, en el Pla per a la llengua i la cohesió social. Educació i convivència intercultural (Departament d’Educació, 2007), Dins de les seves línies estratègiques, aquest Pla contempla el reforç de la xarxa estable de l’entorn escolar amb la col•laboració dels diferents serveis i recursos municipals (entitats d'àmbit social, cultural o esportiu), a través d’iniciatives com els Plans Educatius d’Entorn (PEE).

Local character of magnetic coupling in ionic solids

Magnetic interactions in ionic solids are studied using parameter-free methods designed to provide accurate energy differences associated with quantum states defining the Heisenberg constant J. For a series of ionic solids including KNiF3, K2NiF4, KCuF3, K2CuF4, and high- Tc parent compound La2CuO4, the J experimental value is quantitatively reproduced. This result has fundamental implications because J values have been calculated from a finite cluster model whereas experiments refer to infinite solids. The present study permits us to firmly establish that in these wide-gap insulators, J is determined from strongly local electronic interactions involving two magnetic centers only thus providing an ab initio support to commonly used model Hamiltonians.

La mania de les llistes: 100 biblioteques digitals i 'recol·lectors' de llibres electrònics

Selecció personal de 100 projectes de digitalització internacionals i locals actualment en funcionament. La tria s'ha fet seguint l'interès que poden tenir les obres incloses i en altres ocasions pels serveis, les eines i les aplicacions diferents que s'hi proposen. La major part dels recursos tenen com a objectiu oferir una còpia digital de llibres però també s'hi inclouen altres tipologies documentals: publicacions periòdiques, tesis, literatura grisa, fotografies, gravats, enregistraments sonors¿ Hi abunden els projectes fets per les biblioteques nacionals i universitàries, els projectes comercials més representatius i les col·leccions col·laboratives. Una tipologia a destacar és la de les plataformes que pretenen recuperar i difondre una cultura o una llengua. La llista inclou preferentment projectes de biblioteques digitals amb obres de domini públic, les obres de les quals es poden descarregar i imprimir; també hi són inclosos però materials de pagament. L'ordenació de la selecció està presentada alfabèticament.

From local groups to early states: the development of complexity in protohistoric Catalonia

La recerca sobre la protohistoria de Catalunya s'ha fonamentat tradicionalment en la historia cultural, pero el treba11 deIs darrers vint-i-cinc anys ha comenat a donar 11um sobre aspectes crucials com el canvi social i la formació de l'Estat arcaico Aquest article és una visió general sobre aquests temes. S'hi analitza particularment el paper del creixement demogrMic com a element crucial del canvi social, pero també s'hi té en compte el paper que eventualment hi hagin pogut tenir els moviments de població i el comerç colonial.