Origin of the neutron skin thickness of 208Pb in nuclear mean-field models

We study whether the neutron skin thickness Δrnp of 208Pb originates from the bulk or from the surface of the nucleon density distributions, according to the mean-field models of nuclear structure, and find that it depends on the stiffness of the nuclear symmetry energy. The bulk contribution to Δrnp arises from an extended sharp radius of neutrons, whereas the surface contribution arises from different widths of the neutron and proton surfaces. Nuclear models where the symmetry energy is stiff, as typical of relativistic models, predict a bulk contribution in Δrnp of 208Pb about twice as large as the surface contribution. In contrast, models with a soft symmetry energy like common nonrelativistic models predict that Δrnp of 208Pb is divided similarly into bulk and surface parts. Indeed, if the symmetry energy is supersoft, the surface contribution becomes dominant. We note that the linear correlation of Δrnp of 208Pb with the density derivative of the nuclear symmetry energy arises from the bulk part of Δrnp. We also note that most models predict a mixed-type (between halo and skin) neutron distribution for 208Pb. Although the halo-type limit is actually found in the models with a supersoft symmetry energy, the skin-type limit is not supported by any mean-field model. Finally, we compute parity-violating electron scattering in the conditions of the 208Pb parity radius experiment (PREX) and obtain a pocket formula for the parity-violating asymmetry in terms of the parameters that characterize the shape of the 208Pb nucleon densities.

Microscopic origin of exchange bias in core/shell nanoparticles

We report the results of Monte Carlo simulations with the aim to clarify the microscopic origin of exchange bias in the magnetization hysteresis loops of a model of individual core/shell nanoparticles. Increase of the exchange coupling across the core/shell interface leads to an enhancement of exchange bias and to an increasing asymmetry between the two branches of the loops which is due to different reversal mechanisms. A detailed study of the magnetic order of the interfacial spins shows compelling evidence that the existence of a net magnetization due to uncompensated spins at the shell interface is responsible for both phenomena and allows to quantify the loop shifts directly in terms of microscopic parameters with striking agreement with the macroscopic observed values.

Comparative genomics of the odorant-binding and chemosensory protein gene families across the arthropoda: origin and evolutionary history of the chemosensory system

Chemoreception is a biological process essential for the survival of animals, as it allows the recognition of important volatile cues for the detection of food, egg-laying substrates, mates or predators, among other purposes. Furthermore, its role in pheromone detection may contribute to evolutionary processes such as reproductive isolation and speciation. This key role in several vital biological processes makes chemoreception a particularly interesting system for studying the role of natural selection in molecular adaptation. Two major gene families are involved in the perireceptor events of the chemosensory system: the odorant-binding protein (OBP) and chemosensory protein (CSP) families. Here, we have conducted an exhaustive comparative genomic analysis of these gene families in twenty Arthropoda species. We show that the evolution of the OBP and CSP gene families is highly dynamic, with a high number of gains and losses of genes, pseudogenes and independent origins of subfamilies. Taken together, our data clearly support the birth-and-death model for the evolution of these gene families with an overall high gene-turnover rate. Moreover, we show that the genome organization of the two families is significantly more clustered than expected by chance and, more important, that this pattern appears to be actively maintained across the Drosophila phylogeny. Finally, we suggest the homologous nature of the OBP and CSP gene families, dating back their MRCA (most recent common ancestor) to 380¿420 Mya, and we propose a scenario for the origin and diversification of these families.

Molecular evidence to suggest the origin of a colonization: Drosophila subobscura in America

Abstract The recent colonization of America by Drosophila subobscura represents a great opportunity for evolutionary biology studies. Knowledge of the populations from which the colonization started would provide an understanding of how genetic composition changed during adaptation to the new environment. Thus, a 793 nucleotide fragment of the Odh (Octanol dehydrogenase) gene was sequenced in 66 chromosomal lines from Barcelona (western Mediterranean) and in 66 from Mt. Parnes (Greece, eastern Mediterranean). No sequence of Odh fragment in Barcelona or Mt. Parnes was identical to any of those previously detected in America. However, an Odh sequence from Barcelona differed in only one nucleotide from another found in American populations. In both cases, the chromosomal lines presented the same inversion: O7, and the Odh gene was located within this inversion. This evidence suggests a possible western Mediterranean origin for the colonization. Finally, the molecular and inversion data indicate that the colonization was not characterized by multiple reintroductions.

On the origin of the North Pacific arcs

We present a new hypothesis that relates global plate tectonics to the formation of marginal basins, island arcs, spreading ridges and arc-shaped mountain belts around the North Pacific Ocean. According to our model, the ellipsoidal-shaped Paleogene basins of the South China Sea, Parece-Vela Basin, Shikoku Basin, Sea of Japan and the Sea of Okhotsk in addition to those of the North American Cordillera can be attributed to the change in plate convergence direction at 42 Ma between the Indoaustralian and Eurasian plates. The new direction of convergence was parallel to the eastern continental margin of Asia and resulted in widespread extension perpendicular to this margin and to the western margin of North America. Both margins form part of a circle parallel to the Indoaustralian-Eurasian direction of convergence.

Origin of a restraining bend in an evolving strike-slip system: The Cenozoic As Pontes basin (NW Spain)

The As Pontes basin (12 km2), NW Iberian Peninsula, is bounded by a double restraining bend of a dextral strike-slip fault, which is related to the western onshore end of the Pyrenean belt. Surface and subsurface data obtained from intensive coal exploration and mining in the basin since the 1960s together with additional structural and stratigraphic sequence analysis allowed us to determine the geometric relationships between tectonic structures and stratigraphic markers. The small size of the basin and the large amount of quality data make the As Pontes basin a unique natural laboratory for improving our understanding of the origin and evolution of restraining bends. The double restraining bend is the end stage of the structural evolution of a compressive underlapping stepover, where the basin was formed. During the first stage (stepover stage), which began ca. 30 Ma ago (latest Rupelian) and lasted 3.4 My, two small isolated basins bounded by thrusts and normal faults were formed. For 1.3 My, the strike-slip faults, which defined the stepover, grew towards each other until joining and forming the double restraining bend, which bounds one large As Pontes basin (transition stage). The history of the basin was controlled by the activity of the double restraining bend for a further 3.4 My (restraining bend stage) and ended in mid-Aquitanian times (ca. 22 Ma).

Delphinium L. subgen Delphinium: origin and evolutionary trends

Les caractéristiques avançades de Delphinium L. subgèn. Delphinium (taxons anuals) son comparades amb les del subgèn. Delphinastrum (DC.) Wang i del subgèn. Oligophyllon Dimitrova (taxons perennes). La morfología floral mostra un intercanvi de funcions entre els petals laterals i els petals superiors i restructura de la inflorescencia de molts taxons anuals afavoreix un augment de les taxes de geitonogàmia-autogàmia. L'evolució dels cariotips és basada en una disminució de la longitud total dels cromosomes i en un increment del grau d'asimetria; el nombre cromosómic roman constant per a totes les especies anuals (2n = 16). Leficàcia de la dispersió de les especies anuals és mes gran que no pas la de les especies perennes, per causa d'un increment en la producció de granes i per l'augment de la flotabilitat, tant a l'aire com a l'aigua. D'altres caractéristiques adaptatives avançades son l'adquisició de noves defenses químiques i l'aparició d'un nou tipus embriogènic. Els nínxols ecologies del subgèn. Delphinium corresponen a habitats oberts i alterats, en comparado amb els habitats estables i relativament tancats dels subgéneros Delphinastrum i Oligophyllon. Es presenta una hipótesi global de les tendencies évolutives observades en anuals vs. perennes en connexió amb consideracions biogeogràfiques, així corn un resum taxonomic final.

Phylogenetic studies in Gnaphalieae (Compositae): The genera Phagnalon Cass. and Aliella Qaiser & Lack

The precise generic delimitation of Aliella andPhagnalon, and their closest relatives within the Gnaphalieae are discussed in this review. Among the main results obtained, wehave found that the genera Aliella and Phagnalon are nested withinthe “Relhania clade” and Anisothrix, Athrixia and Pentatrichia aretheir closest relatives. Macowania is also part of the “Relhaniaclade”, whereas the subtribal affinities of Philyrophyllum liewithin the “crown radiation clade”. The monophyly of Aliellaand Phagnalon is not supported statistically. In addition,Aliella appears to be paraphylethic in most of the analysesperformed. The resulting phylogeny suggests an African origin forthe ancestor of Aliella and Phagnalon and identifies three mainclades within Phagnalon that constitute the following naturalgroups on a geographic basis: (1) the Irano-Turanian clade; (2) the Mediterranean-Macaronesian clade; and (3) the Yemen-Ethiopian clade. Some endemics to Yemen and Ethiopia appeared merged in the Mediterranean-Macaronesian clade, providing new evidence of the phytogeographical links betweenMacaronesia, Eastern Africa and Southern Arabia. Incongruities between thechloroplast and nuclear molecular data and the lack of resolution in some clades mayindicate that hybridization could have played an important role in the evolution anddiversification of both Phagnalon and Aliella.

Identifying the parent-of-origin of de novo SNVs in schizophrenia

Several studies over the last few years have shown that newly arising (de novo) mutations contribute to the genetics of schizophrenia (SZ), autism (ASD) and other developmental disorders. The strongest evidence comes from studies of de novo Copy Number Variation (CNV), where the rate of new mutations is shown to be increased in cases when compared to controls [23, 24]. Research on de novo point mutations and small insertion-deletions (indels) has been more limited, but with the development of next-generation sequencing (NGS) technology, such studies are beginning to provide preliminary evidence that de novo single-nucleotide mutations (SNVs) might also increase risk of SZ and ASD [25, 26] Advanced paternal age is a major source of new mutations in human beings [27] and could thus be associated with increased risk for developing SZ, ASD or other developmental disorders. Indeed, advanced paternal age is found to be a risk factor for developing SZ and ASD in the offspring [28, 29] and new mutations related to advanced paternal age have been implicated as a cause of sporadic cases in several autosomal dominant diseases, some neurodevelopmental diseases, including SZ and ASD, and social functioning. New single-base substitutions occur at higher rates at males compared to females and this difference increases with paternal age. This is due to the fact that sperm cells go through a much higher number of cell divisions (~840 by the age of 50), which increases the risk for DNA copy errors in the male germ line [30] . By contrast, the female eggs (oocytes) undergo only 24 cell divisions and all but the last occur during foetal life. The aim of my project is to determine the parent-of-origin of de novo SNVs, using large samples of parent-offspring trios affected with schizophrenia (SZ). From whole exome sequencing of 618 Bulgarian proband-offspring trios affected, nearly 1000 de novo (SNVs or small indels) have been identified and from these, the parent-of-origin of at least 60% of the mutations (N=600) can be established. This project is contained in a main one that consists on the determination of the parental origin of different types of de novo mutations (SNVs, small indels and large CNVs).

Indicadores cuantitativos de segregación residencial. El caso de la población inmigrante en Barcelona

La segregación residencial en una ciudad indica el nivel de desigualdad de la distribución de la población entre las diferentes zonas. Es interesante obtener una visión cuantitativa de la segregación residencial para prever y actuar sobre los territorios más afectados por este proceso. En este artículo se propone medir la segregación de los colectivos de inmigrantes desde diferentes ópticas, utilizando la estadística espacial y los sistemas de información geográfica. Con estas herramientas se realiza un estudio sobre la distribución de la población inmigrante para la ciudad de Barcelona. Los resultados apuntan a una disminución en la segregación entre 1996 y 2001. Aunque se aprecian diferencias significativas según la procedencia de cada grupo estudiado.

Transcriptome analyses of primitively eusocial wasps reveal novel insights into the evolution of sociality and the origin of alternative phenotypes

BACKGROUND: Understanding how alternative phenotypes arise from the same genome is a major challenge in modern biology. Eusociality in insects requires the evolution of two alternative phenotypes - workers, who sacrifice personal reproduction, and queens, who realize that reproduction. Extensive work on honeybees and ants has revealed the molecular basis of derived queen and worker phenotypes in highly eusocial lineages, but we lack equivalent deep-level analyses of wasps and of primitively eusocial species, the latter of which can reveal how phenotypic decoupling first occurs in the early stages of eusocial evolution. RESULTS: We sequenced 20 Gbp of transcriptomes derived from brains of different behavioral castes of the primitively eusocial tropical paper wasp Polistes canadensis. Surprisingly, 75% of the 2,442 genes differentially expressed between phenotypes were novel, having no significant homology with described sequences. Moreover, 90% of these novel genes were significantly upregulated in workers relative to queens. Differential expression of novel genes in the early stages of sociality may be important in facilitating the evolution of worker behavioral complexity in eusocial evolution. We also found surprisingly low correlation in the identity and direction of expression of differentially expressed genes across similar phenotypes in different social lineages, supporting the idea that social evolution in different lineages requires substantial de novo rewiring of molecular pathways. CONCLUSIONS: These genomic resources for aculeate wasps and first transcriptome-wide insights into the origin of castes bring us closer to a more general understanding of eusocial evolution and how phenotypic diversity arises from the same genome.