177 research outputs found

    Hunting WIMPs with LISA: Correlating dark matter and gravitational wave signals

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    The thermal freeze-out mechanism in its classical form is tightly connected to physics beyond the Standard Model around the electroweak scale, which has been the target of enormous experimental efforts. In this work we study a dark matter model in which freeze-out is triggered by a strong first-order phase transition in a dark sector, and show that this phase transition must also happen close to the electroweak scale, i.e. in the temperature range relevant for gravitational wave searches with the LISA mission. Specifically, we consider the spontaneous breaking of a U(1)′U(1)^\prime gauge symmetry through the vacuum expectation value of a scalar field, which generates the mass of a fermionic dark matter candidate that subsequently annihilates into dark Higgs and gauge bosons. In this set-up the peak frequency of the gravitational wave background is tightly correlated with the dark matter relic abundance, and imposing the observed value for the latter implies that the former must lie in the milli-Hertz range. A peculiar feature of our set-up is that the dark sector is not necessarily in thermal equilibrium with the Standard Model during the phase transition, and hence the temperatures of the two sectors evolve independently. Nevertheless, the requirement that the universe does not enter an extended period of matter domination after the phase transition, which would strongly dilute any gravitational wave signal, places a lower bound on the portal coupling that governs the entropy transfer between the two sectors. As a result, the predictions for the peak frequency of gravitational waves in the LISA band are robust, while the amplitude can change depending on the initial dark sector temperature.Comment: 29 pages, 12 figures + appendice

    Equilibrium to off-equilibrium crossover in homogeneous active matter

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    We study the crossover between equilibrium and off-equilibrium dynamical universality classes in the Vicsek model near its ordering transition. Starting from the incompressible hydrodynamic theory of Chen et al \cite{chen2015critical}, we show that increasing the activity leads to a renormalization group (RG) crossover between the equilibrium ferromagnetic fixed point, with dynamical critical exponent z=2z = 2, and the off-equilibrium active fixed point, with z=1.7z = 1.7 (in d=3d=3). We run simulations of the classic Vicsek model in the near-ordering regime and find that critical slowing down indeed changes with activity, displaying two exponents that are in remarkable agreement with the RG prediction. The equilibrium-to-off-equilibrium crossover is ruled by a characteristic length scale beyond which active dynamics takes over. Such length scale is smaller the larger the activity, suggesting the existence of a general trade-off between activity and system's size in determining the dynamical universality class of active matter.Comment: 10 pages, 4 figure

    RAPHAEL: recognition, periodicity and insertion assignment of solenoid protein structures.

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    Abstract Motivation: Repeat proteins form a distinct class of structures where folding is greatly simplified. Several classes have been defined, with solenoid repeats of periodicity between ca. 5 and 40 being the most challenging to detect. Such proteins evolve quickly and their periodicity may be rapidly hidden at sequence level. From a structural point of view, finding solenoids may be complicated by the presence of insertions or multiple domains. To the best of our knowledge, no automated methods are available to characterize solenoid repeats from structure. Results: Here we introduce RAPHAEL, a novel method for the detection of solenoids in protein structures. It reliably solves three problems of increasing difficulty: (1) recognition of solenoid domains, (2) determination of their periodicity and (3) assignment of insertions. RAPHAEL uses a geometric approach mimicking manual classification, producing several numeric parameters that are optimized for maximum performance. The resulting method is very accurate, with 89.5% of solenoid proteins and 97.2% of non-solenoid proteins correctly classified. RAPHAEL periodicities have a Spearman correlation coefficient of 0.877 against the manually established ones. A baseline algorithm for insertion detection in identified solenoids has a Q2 value of 79.8%, suggesting room for further improvement. RAPHAEL finds 1931 highly confident repeat structures not previously annotated as solenoids in the Protein Data Bank records. Availability: The RAPHAEL web server is available with additional data at http://protein.bio.unipd.it/raphael/ Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics onlin

    A political ecology of green territorialization: frontier expansion and conservation in the Colombian Amazon

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    After decades of civil war, the Colombian government has recently declared the Amazon as a model region for green growth and low carbon development. The Amazon Vision programme, launched by the Colombian government in 2016, seeks to contribute to forest conservation, climate mitigation, poverty reduction and peace building. The Amazon Vision fundamentally reframes the Colombian Amazon from a ‘narco frontier’ that needs to be liberated from guerrilla influence, organized crime and peasants destroying forests for coca cultivation, to a net CO2 sink with enormous potential for green growth and poverty reduction. Drawing on historical and empirical qualitative research in Guaviare and complemented by a quantitative land cover classification, this article builds on the concept of ‘green territoriality’ to investigate the extent to which the shift towards conservation affects property rights and the ability of indigenous groups and peasants to access land and natural resources. We illustrate how the reframing of peasants from protagonists of development and frontier expansion to villains, and of indigenous communities from underdeveloped forest dwellers to environmental guardians, has created land conflicts and affected the legitimacy of their respective property rights. In both cases, the Amazon Vision strengthens conservation policies and challenges existing land rights but also creates new windows of opportunity for the land claims of indigenous communities while reinforcing conceptualizations of social differentiation among dwellers of the Amazon

    The westward lithospheric drift, its role on the subduction and transform zones surrounding Americas: Andean to Cordilleran orogenic types cyclicity

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    We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main structural grain and kinematics of the Andes and Sandwich arc slabs. In the Andes, the subduction zone is shallow and with low dip, because the mantle flow sustains the slab; the subduction hinge converges relative to the upper plate and generates an uplifting doubly verging orogen. The Sandwich Arc is generated by a westerly-directed SAM (South American) plate subduction where the eastward mantle flow is steepening and retreating the subduction zone. In this context, the slab hinge is retreating relative to the upper plate, generating the backarc basin and a low bathymetry single-verging accretionary prism. In Central America, the Caribbean plate presents a more complex scenario: (a) To the East, the Antilles Arc is generated by westerly directed subduction of the SAM plate, where the eastward mantle flow is steepening and retreating the subduction zone. (b) To the West, the Middle America Trench and Arc are generated by the easterly-directed subduction of the Cocos plate, where the shallow subduction caused by eastward mantle flow in its northern segment gradually steepens to the southern segment as it is infered by the preexisting westerly-directed subduction of the Caribbean Plateau.In the frame of the westerly lithospheric flow, the subduction of a divergent active ridge plays the role of introducing a change in the oceanic/continental plate's convergence angle, such as in NAM (North American) plate with the collision with the Pacific/Farallon active ridge in the Neogene (Cordilleran orogenic type scenario). The easterly mantle drift sustains strong plate coupling along NAM, showing at Juan de Fuca easterly subducting microplate that the subduction hinge advances relative to the upper plate. This lower/upper plate convergence coupling also applies along strike to the neighbor continental strike slip fault systems where subduction was terminated (San Andreas and Queen Charlotte). The lower/upper plate convergence coupling enables the capture of the continental plate ribbons of Baja California and Yakutat terrane by the Pacific oceanic plate, transporting them along the strike slip fault systems as para-autochthonous terranes. This Cordilleran orogenic type scenario, is also recorded in SAM following the collision with the Aluk/Farallon active ridge in the Paleogene, segmenting SAM margin into the eastwardly subducting Tupac Amaru microplate intercalated between the proto-Liquiñe-Ofqui and Atacama strike slip fault systems, where subduction was terminated and para-autochthonous terranes transported. In the Neogene, the convergence of Nazca plate with respect to SAM reinstalls subduction and the present Andean orogenic type scenario

    Large scale phenotyping and molecular analysis in a germplasm collection of rocket salad (Eruca vesicaria) reveal a differentiation of the gene pool by geographical origin

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    [EN] Cultivated rocket (Eruca vesicaria) is a leafy vegetable highly appreciated for its healthpromoting virtues and consumed both raw and cooked as ready-to-use vegetable. Despite Eruca being cultivated worldwide, only a few cultivars are available and limited breeding activities have been carried out so far. Therefore, the genetic resources available represent an unexploited potential source of variation for breeding. In the present study, 155 E. vesicaria accessions from 30 countries across Europe, Asia, Africa, and America have been characterized for 54 qualitative and quantitative morphological and quality traits. Conventional descriptors and automated tools for the determination of the quality, morphology, and colour of leaves have been used. Genetic diversity was assessed using 15 inter simple sequence repeat and simple sequence repeat markers. A high level of diversity was evidenced in the collection. Significant differences were found in most of the traits with the exception of five pseudo-qualitative descriptors. The first and second dimensions of the principal components analysis with phenotypic traits accounted for 25.69% of total variation showing a stratification of the genotypes according to the European and Asian origins. In total, 75% of the variation was contained in the first 15 components having eigenvalues higher than 1.0. Also, the population structure divided the collection into two main clusters separating European genotypes from the rest. Furthermore, hierarchical cluster analysis confirmed a geographical separation, grouping the accessions into three major clusters, which were differentiated by plant architecture, leaf and flower colour, leaf water status, leaf blade shape and hairiness of the leaves and stem. Our approach has broadened the knowledge of the diversity within the Eruca gene pool, thus contributing to identify sources of variation and to select the best candidates for cultivated rocket breeding programs, as well as to determine the genetic basis of plant and leaf traits in future genome-wide association studies.The work was supported by 'RGV-FAO' project funded by the Italian Ministry of Agriculture, Food and Forestry. C. Guijarro-Real thanks the Ministerio de Educacion, Cultura y Deporte of Spain (MECD) for its financial support by means of a predoctoral FPU Grant (FPU14/06798), and for the specific grant for mobility (EST17/00354) from the same Organization.Guijarro-Real, C.; Navarro, A.; Esposito, S.; Festa, G.; Macellaro, R.; Di Cesare, C.; Fita, A.... (2020). Large scale phenotyping and molecular analysis in a germplasm collection of rocket salad (Eruca vesicaria) reveal a differentiation of the gene pool by geographical origin. 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    Development of a Novel Perfusable Solution for ex vivo Preservation: Towards Photosynthetic Oxygenation for Organ Transplantation

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    Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation

    Consumer Attitudes towards Microalgae Production and Microalgae-Based Agricultural Products: The Cases of Almería (Spain) and Livorno (Italy)

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    The production of microalgal biomass and products derived thereof for a wide variety of applications is a hot research topic, with the number of facilities being built and products and biologically active molecules launched into the market increasing every year. The aim of the current study was to identify the attitudes of citizens in Almería (Spain) and Livorno (Italy) towards the construction of a microalgae production plant and a biorefinery in their cities and also their opinions about the microalgae-based products that could be produced. Overall, in Almería (Spain), a NIMBY (not in my back yard) attitude towards the construction of a microalgal production facility and especially towards a microalgal biorefinery was observed, despite the strong microalgal industry in the region and the higher knowledge of citizens about microalgae. In both locations, but especially in Livorno (Italy), microalgae-based biostimulants, biofertilisers, and aquafeeds were well accepted. Proximity was the main factor affecting the acceptance of a microalgae producing facility. Consumer knowledge about microalgal biotechnology and the health and environmental benefits of this valuable raw material are scarce, and opinions are based on drivers other than knowledge. After gaining more knowledge about microalgal biorefineries, most of the responses in Almería (47%) and Livorno (61%) were more positiv

    Renormalization group crossover in the critical dynamics of field theories with mode coupling terms

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    Motivated by the collective behavior of biological swarms, we study the critical dynamics of field theories with coupling between order parameter and conjugate momentum in the presence of dissipation. Under a fixed-network approximation, we perform a dynamical renormalization group calculation at one loop in the near-critical disordered region, and we show that the violation of momentum conservation generates a crossover between an unstable fixed point, characterized by a dynamic critical exponent z = d/2, and a stable fixed point with z = 2. Interestingly, the two fixed points have different upper critical dimensions. The interplay between these two fixed points gives rise to a crossover in the critical dynamics of the system, characterized by a crossover exponent κ = 4/d. The crossover is regulated by a conservation length scale R0, given by the ratio between the transport coefficient and the effective friction, which is larger as the dissipation is smaller: Beyond R0, the stable fixed point dominates, while at shorter distances dynamics is ruled by the unstable fixed point and critical exponent, a behavior which is all the more relevant in finite-size systems with weak dissipation. We run numerical simulations in three dimensions and find a crossover between the exponents z = 3/2 and z = 2 in the critical slowdown of the system, confirming the renormalization group results. From the biophysical point of view, our calculation indicates that in finite-size biological groups mode coupling terms in the equation of motion can significantly change the dynamical critical exponents even in the presence of dissipation, a step toward reconciling theory with experiments in natural swarms. Moreover, our result provides the scale within which fully conservative Bose-Einstein condensation is a good approximation in systems with weak symmetry-breaking terms violating number conservation, as quantum magnets or photon gases.Instituto de Física de Líquidos y Sistemas Biológico
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