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This work aims at improving the resilience and damage tolerant properties of CFRP by using cork, which is a natural material with good energy absorption capacity and thermal insulating and vibration damping characteristics. Two types of materials were considered: a sandwich formed by carbon-epoxy facesheets with a cork-epoxy core and a carbon-epoxy laminate with embedded cork granulates. The damage tolerant properties were evaluated by low velocity impact tests according to the type of material. Additionally, this work intends to evaluate the feasibility of using a cork agglomerate combined with CFRP in a sandwich configuration in order to improve the aeroelastic properties of certain types of aerospace components aiming at preventing the occurrence of damage due to flutter. A computational analysis was used to determine the critical flutter speed of a cork based sandwich plate and other conventional materials, such as aluminium alloy and CFRP.
Results are clear about the benefits of using cork based composites either by improving the damage tolerant properties under impact loading or by extending the flight envelope without weight penalty by increasing the flutter critical speed.
Leishmania (Viannia) braziliensis and L. (V.) peruviana are two parasite species characterized by a very different pathogenicity in humans despite a high genetic similarity. We hypothesized previously that L. (V.) peruviana would descend from L. (V.) braziliensis and would have acquired its ‘peruviana’ character during the southward colonization and adaptation of the transmission cycle in the Peruvian Andes. In order to have a first appreciation of the differences in virulence between both species, we evaluated an in vitro and in vivo model for experimental infection. A procedure was adapted to enrich culture forms in infective stages and the purified metacyclics were used to infect macrophage cell lines and golden hamsters. The models were tested with 2 representative strains of L. (V.) braziliensis from cutaneous and mucosal origin respectively and 2 representative strains of L. (V.) peruviana from Northern and Southern Peru respectively. Our models were reproducible and sensitive enough to detect phenotypic differences among strains. We showed in vitro as well as in vivo that the L. (V.) braziliensis was more infective than L. (V.) peruviana. Furthermore, we found that in vitro infectivity patterns of the 4 strains analysed, were in agreement with the geographical structuring of parasite populations demonstrated in our previous studies. Further work is needed to confirm our results with more strains of different geographical origin and their specific clinical outcome. However, our data open new perspectives for understanding the process of speciation in Leishmania and its implications in terms of pathogenicity.
We study compact Riemann surfaces of genus $g\geq2$ having a dihedral group of automorphisms. We find necessary and sufficient conditions on the signature of a Fuchsian group for it to admit a surface kernel epimorphism onto the dihedral group $D_N$. The question of extendability of the action of $D_N$ is considered. We also give an explicit parametrization of the moduli space of Riemann surfaces with maximal dihedral symmetry, showing that it is a one-dimensional complex manifold. Defining equations of all such surfaces and the formulae of their automorphisms are calculated. The locus of this moduli space consisting of those surfaces admitting some real structure is determined.
E. Bujalance, Universidad National de Educación a Distancia, Madrid,A. F. Costa, Universidad National de Educación a Distancia, Madrid,E. Martínez, Universidad National de Educación a Distancia, Madrid
In this paper we study the algebraic structure of the hyperelliptic mapping class group of Klein surfaces, which is closely related to the mapping class group of punctured discs. This group plays an important role in the study of the moduli space of hyperelliptic real algebraic curves. Our main result provides a presentation by generators and relations for the hyperelliptic mapping class group of surfaces of prescribed topological type.
In the nineteenth century, Hurwitz  and Wiman  obtained bounds for the order of the automorphism group and the order of each automorphism of an orientable and unbordered compact Klein surface (i. e., a compact Riemann surface) of topological genus g s 2. The corresponding results of bordered surfaces are due to May, , . These may be considered as particular cases of the general problem of finding the minimum topological genus of a surface for which a given finite group G is a group of automorphisms. This problem was solved for cyclic and abelian G by Harvey  and Maclachlan , respectively, in the case of Riemann surfaces and by Bujalance , Hall  and Gromadzki  in the case of non-orientable and unbordered Klein surfaces. In dealing with bordered Klein surfaces, the algebraic genus—i. e., the topological genus of the canonical double covering, (see Alling-Greenleaf )—was minimized by Bujalance- Etayo-Gamboa-Martens  in the case where G is cyclic and by McCullough  in the abelian case.
Photoluminescence from porous silicon can be quenched reversibly by a variety of molecular species. Quenching pathways for chemically incorporated surface species, physisorbed species (that undergo no net chemical transformation), and for electron donating reagents have all been identified. For systems involving charge transfer quenching, the concentration dependence typically follows a Stern-Volmer type of relationship, with the more easily oxidized molecules producing the largest Stern-Volmer slopes (most efficient quenching). The slope of the Stern-Volmer plot is dependent upon the particular wavelength that the Stern-Volmer data are obtained from. Data interpretation is complicated by the fact that porous Si shows a wavelength dependent emission lifetime, although when this is taken into account the data can be qualitatively described within the context of a driving-force dependent quenching model. A simple model for understanding the various photoluminescence quenching phenomena observed with porous Si is presented, involving an ensemble of emissive states with energy dependent lifetimes and Stern-Volmer quenching behavior. The model adequately accounts for both red and blue spectral shifts that have been observed upon photoluminescence quenching.
Approximately 140 gynes of the paper wasp, Polistes fuscatus, were overwintered in the laboratory with their natal nest and nestmates. After a 14 day isolation period, three marked female nestmates were placed into a nesting box with three marked female nestmates from a presumably unrelated colony. Fifteen nesting boxes were constructed, each with six gynes from two different sister groups. The identities of paired gynes (spaced ≤5 cm apart) and foundresses on nests were recorded in blind observations. Sisters preferentially paired (P <.0001) prior to nesting. Of 18 foundress associations formed at newly constructed nests, 16 consisted of sister groups.
Seasonal morphometric analysis of 788 adult Polistes metricus Say showed that: (1) Queens sampled throughout the colony cycle were of similar body size but significantly smaller than fall gynes. (2) Queens’ ovaries are large in the spring, decline early in the colony cycle, peak near the mid-postemergence period and decline late in the colony cycle. (3) There are no significant correlations between head width, ovary width, and size of nest in workers or queens. (4) Early and late workers are small but workers emerging during the mid-postemergence period are large. (5) All workers and gynes emerge with small, similar sized ovaries but older workers may develop larger ovaries. (6) Queens are larger than early and late workers but the same size as workers emerging during the mid-postemergence period. (7) The class with the largest adults were intermediates collected when colonies began production of males. These adults, intermediate in fat content between workers and gynes, comprised a large proportion of females emerging late in the colony cycle. (8) The body size of gynes is independent of colony size. (9) Males were significantly more variable in body size than gynes.
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