We describe the genetic code in terms of numbers that help us to find several dual symmetries. Our formulation can even be rewritten regarding the up-down and right-left dual concepts. We argue that ...our work may bring many topological tools to studying the DNA molecule, including the Grassmann-Plücker coordinates, which are important in mathematical and physical contexts.
Summary
Background
Eosinophils, a central factor in asthma pathogenesis, have the ability to secrete exosomes. However, the precise role played by exosomes in the biological processes leading up to ...asthma has not been fully defined.
Objective
We hypothesized that exosomes released by eosinophils contribute to asthma pathogenesis by activating structural lung cells.
Methods
Eosinophils from asthmatic patients and healthy volunteers were purified from peripheral blood, and exosomes were isolated from eosinophils of asthmatic and healthy individuals. All experiments were performed with eosinophil‐derived exosomes from healthy and asthmatic subjects. Epithelial damage was evaluated using primary small airway epithelial cell lines through 2 types of apoptosis assays, that is, flow cytometry and TUNEL assay with confocal microscopy. Additionally, the epithelial repair was analysed by performing wound healing assays with epithelial cells. Functional studies such as proliferation and inhibition‐proliferation assays were carried out in primary bronchial smooth muscle cell lines. Also, gene expression analysis of pro‐inflammatory molecules was evaluated by real‐time PCR on epithelial and muscle cells. Lastly, protein expression of epithelial and muscle cell signalling factors was estimated by Western blot.
Results
Asthmatic eosinophil‐derived exosomes induced an increase in epithelial cell apoptosis at 24 hour and 48 hour, impeding wound closure. In addition, muscle cell proliferation was increased at 72 hours after exosome addition and was linked with higher phosphorylation of ERK1/2. We also found higher expression of several genes when both cell types were cultured in the presence of exosomes from asthmatics: CCR3 and VEGFA in muscle cells, and CCL26, TNF and POSTN in epithelial cells. Healthy eosinophil‐derived exosomes did not exert any effect over these cell types.
Conclusions and Clinical Relevance
Eosinophil‐derived exosomes from asthmatic patients participate actively in the development of the pathological features of asthma via structural lung cells.
The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative ...stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.
In group-living species, social stability is an important trait associated with the evolution of complex behaviours such as cooperation. While the drivers of stability in small groups are relatively ...well studied, little is known about the potential impacts of unstable states on animal societies. Temporary changes in group composition, such as a social group splitting and recombining (i.e. a disturbance event), can result in individuals having to re-establish their social relationships, thus taking time away from other tasks such as foraging or vigilance. Here, we experimentally split socially stable groups of captive zebra finches (Taeniopygia guttata), and quantified the effects of repeated disturbance events on (1) group foraging efficiency, and (2) co-feeding associations when subgroups were recombined. We found that the efficiency of groups to deplete a rich, but ephemeral, resource patch decreased after just a single short disturbance event. Automated tracking of individuals showed that repeated disturbances reduced efficiency by causing social relationships to become more differentiated and weaker, resulting in fewer individuals simultaneously accessing the patch. Our experiment highlights how short-term disturbances can severely disrupt social structure and group functionality, revealing potential costs associated with group instability that can have consequences for the evolution of animal societies.
The effect of material orientation on void growth Hosseini, N.; Nieto-Fuentes, J.C.; Dakshinamurthy, M. ...
International journal of plasticity,
January 2022, 2022-01-00, 20220101, Letnik:
148
Journal Article
Recenzirano
Odprti dostop
•Unit-cell finite element calculations with prescribed Lode parameter and stress triaxiality.•Material yielding defined by the orthotropic Yld2004-18p criterion.•Void growth is affected by material ...orientation.•The misalignment between loading and orthotropy axes triggers a minimum void growth.
In this work, we have brought to light the effect of material orientation on void growth. For that purpose, we have performed finite element calculations using a cubic unit-cell model with a spherical void at its center and subjected to periodic boundary conditions. The behavior of the material is described with an elastic isotropic, plastic orthotropic constitutive model with yielding defined by Yld2004-18p criterion (Barlat et al., 2005). We have used the multi-point constraint subroutine developed by Dakshinamurthy et al. (2021) to enforce constant values of macroscopic stress triaxiality T and Lode parameter L in calculations that have been carried out for different stress states resulting from the combination of T=0.33, 1 and 2, with L=−1, 0 and 1 (axisymmetric tension, generalized shear and axisymmetric compression, respectively). Firstly, we have performed numerical simulations in which the loading directions are collinear with the orthotropy axes of the material, so that the principal directions of macroscopic stress and strain are parallel. Investigation of the cases for which the minor loading axis coincides either with the rolling, the transverse or the normal direction, has shown that the initially spherical void turns into an ellipsoid whose rate of growth and eccentricity depend on both stress state and material orientation. A key result is that for specific material orientations the anisotropy switches the effect of Lode parameter on void growth, reversing the trends obtained for isotropic von Mises materials. Secondly, we have carried out calculations using a novel strategy which consists of including angular misalignments within the range 0∘≤θ≤90∘, so that one loading direction is parallel to one of the symmetry axes of the material, and θ is the angle formed between the other two loading directions and the second and third orthotropy axes. In fact, to the authors’ knowledge, these are the first unit-cell calculations ever reported in which the material is modeled using a macroscopic anisotropic yield function with prescribed misalignment between loading and material axes and, at the same time, the macroscopic stress triaxiality and the Lode parameter are controlled to be constant during loading. The finite element calculations have shown that the misalignment between loading and material axes makes the void and the faces of the unit-cell to rotate and twist during loading. Moreover, the main contribution of this work is the identification of an intermediate value of the angle θ for which the growth rate of the void reaches an extreme value (minimum or maximum), so that the numerical results indicate that material orientation and angular misalignment can be strategically exploited to control void growth, and thus promote or delay localization and fracture of anisotropic metal products. The conclusions of this research have been shown to be valid for three different materials (aluminum alloys 2090-T3, 6111-T4 and 6013) and selected comparisons have also been performed using two additional yield criteria (CPB06ex2 and Yld2011-27p).
This paper presents a Negative Stiffness System (NSS) based on a set of two double–acting pneumatic linear actuators (PLA). The NSS is added to a system with a single degree of freedom, which ...consists of a sprung mass and a pneumatic spring. One end of each PLA is jointed to the sprung mass while the other end is jointed to the vibrating frame. In addition, the PLAs are symmetrically arranged so that they remain horizontal while the sprung mass is in static conditions. When the rear chamber is pressurised, the vertical component of the force applied by the PLAs will work against the pneumatic spring reducing the dynamic resonance frequency of the overall system. Experimental tests and simulations showed improvements regarding sprung mass isolation in comparison to the passive system without NSS, decreasing the resonance frequency by up to 58% and improving the vibration attenuation for different experimental excitations.
We assess the spatial structure of moisture flux divergence, regional moisture sources and transport processes over Colombia, in northern South America. Using three independent methods the dynamic ...recycling model (DRM), FLEXPART and the Quasi-isentropic back-trajectory (QIBT) models we quantify the moisture sources that contribute to precipitation over the region. We find that moisture from the Atlantic Ocean and terrestrial recycling are the most important sources of moisture for Colombia, highlighting the importance of the Orinoco and Amazon basins as regional providers of atmospheric moisture. The results show the influence of long-range cross-equatorial flow from the Atlantic Ocean into the target region and the role of the study area as a passage of moisture into South America. We also describe the seasonal moisture transport mechanisms of the well-known low-level westerly and Caribbean jets that originate in the Pacific Ocean and Caribbean Sea, respectively. We find that these dynamical systems play an important role in the convergence of moisture over western Colombia.
Background and aims Jurinea pinnata is an Iberian vascular plant which only grows on gypsum and dolomite, two types of rocks associated with their exclusive endemic floras. In addition, the plant has ...an island-like distribution which could affect the differentiation and the genetic variability of wild populations. Thus, the species provides a unique opportunity for comparing (bio) geographical and ecological (edaphic) differentiation by means of molecular markers. Methods For our investigation we took 24 soil samples paired with a similar number of foliar samples for nutritional analyses. Our molecular-marker approach (AFLPs) involved 16 populations. Results The edaphic parameters revealed significant dissimilarities between dolomitic and gypsum soils. These differences are also found in the mineral composition of the leaves. However, molecular data revealed that the differentiation between populations correlates better with geographical isolation than with the substrate character. Conclusions The populations showing the greatest genetic diversity are those of the East Baetic territory where the species grow on both substrates and its populations are closer together. The plant tolerance to gypsum and dolomite can be explained either as a result of common adaptive mechanisms or of a more general adaptation to arid environments.
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