Examining the growth and evolution of magnetic fields in clusters of galaxies: a numerical perspective

Magnetic fields are ubiquitous in galaxy cluster atmospheres and have a variety of astrophysical and cosmological consequences. Magnetic fields can contribute to the pressure support of clusters, affect thermal conduction, and modify the evolution of bubbles driven by active galactic nuclei. However, we currently do not fully understand the origin and evolution of these fields throughout cosmic time. Furthermore, we do not have a general understanding of the relationship between magnetic field strength and topology and other cluster properties, such as mass and X-ray luminosity. We can now begin to answer some of these questions using large-scale cosmological magnetohydrodynamic (MHD) simulations of the formation of galaxy clusters including the seeding and growth of magnetic fields. Using large-scale cosmological simulations with the FLASH code combined with a simplified model of the acceleration of cosmic rays responsible for the generation of radio halos, we find that the galaxy cluster frequency distribution and expected number counts of radio halos from upcoming low-frequency sur- veys are strongly dependent on the strength of magnetic fields. Thus, a more complete understanding of the origin and evolution of magnetic fields is necessary to understand and constrain models of diffuse synchrotron emission from clusters. One favored model for generating magnetic fields is through the amplification of weak seed fields in active galactic nuclei (AGN) accretion disks and their subsequent injection into cluster atmospheres via AGN-driven jets and bubbles. However, current large-scale cosmological simulations cannot directly include the physical processes associated with the accretion and feedback processes of AGN or the seeding and merging of the associated SMBHs. Thus, we must include these effects as subgrid models. In order to carefully study the growth of magnetic fields in clusters via AGN-driven outflows, we present a systematic study of SMBH and AGN subgrid models. Using dark-matter only cosmological simulations, we find that many important quantities, such as the relationship between SMBH mass and galactic bulge velocity dispersion and the merger rate of black holes, are highly sensitive to the subgrid model assumptions of SMBHs. In addition, using MHD calculations of an isolated cluster, we find that magnetic field strengths, extent, topology, and relationship to other gas quantities such as temperature and density are also highly dependent on the chosen model of accretion and feedback. We use these systematic studies of SMBHs and AGN inform and constrain our choice of subgrid models, and we use those results to outline a fully cosmological MHD simulation to study the injection and growth of magnetic fields in clusters of galaxies. This simulation will be the first to study the birth and evolution of magnetic fields using a fully closed accretion-feedback cycle, with as few assumptions as possible and a clearer understanding of the effects of the various parameter choices.

Bioeconomic modelling of woody regrowth carbon offset options in productive grazing systems

Agricultural land has been identified as a potential source of greenhouse gas emissions offsets through biosequestration in vegetation and soil. In the extensive grazing land of Australia, landholders may participate in the Australian Government’s Emissions Reduction Fund and create offsets by reducing woody vegetation clearing and allowing native woody plant regrowth to grow. This study used bioeconomic modelling to evaluate the trade-offs between an existing central Queensland grazing operation, which has been using repeated tree clearing to maintain pasture growth, and an alternative carbon and grazing enterprise in which tree clearing is reduced and the additional carbon sequestered in trees is sold. The results showed that ceasing clearing in favour of producing offsets produces a higher net present value over 20 years than the existing cattle enterprise at carbon prices, which are close to current (2015) market levels (~$13 t–1 CO2-e). However, by modifying key variables, relative profitability did change. Sensitivity analysis evaluated key variables, which determine the relative profitability of carbon and cattle. In order of importance these were: the carbon price, the gross margin of cattle production, the severity of the tree–grass relationship, the area of regrowth retained, the age of regrowth at the start of the project, and to a lesser extent the cost of carbon project administration, compliance and monitoring. Based on the analysis, retaining regrowth to generate carbon income may be worthwhile for cattle producers in Australia, but careful consideration needs to be given to the opportunity cost of reduced cattle income.

Floral expression and pollen germination ability in productive mountain papaya ( Vasconcellea pubescens A.DC.) orchards

Mountain papaya ( Vasconcellea pubescens A.DC.) is described as trioecious in the centers of origin of Ecuador, Colombia, and Peru. However, under cultivation conditions in La Serena (30° S, 70° W), Chile, it is found to be dioecious and monoecious. The objective was to learn about the variations in floral expression of mountain papaya. Flowers from monoecious and dioecious plants were therefore identified and quantified during two seasons. In vitro pollen germination ability was also evaluated based on the factors of site, season, and plant sex. Monoecious plant inflorescences are polygamous; female and male flowers are observed, as well as bisexual flowers that are usually deformed. This condition allows them to be classified as an ambisexual plant. The existence of flowers of different sexes appears to depend on the season; the female dioecious plant is maintained as such, independently of climatic conditions. Pollen from male flowers, from both ambisexual and male plants, germinates 75% in summer, while germination decreases to 56% in spring (P ≤ 0.05). Flowering of female plants coincides with the permanent occurrence of male flowers in ambisexual plants, which ensures pollination without the need for male plants as pollinators in orchards. Based on this information, some management practices and possible lines of research about this species are proposed.

Effects of organic fertilizers on the vegetative, nutritional, and productive parameters of blueberries ‘Corona’, ‘Legacy’, and ‘Liberty’

Organic farming does not allow using certain inputs, such as N, which differ in nutrient release rates and dynamics. To evaluate the effect of different organic fertilizers on the vegetative, nutritional, and productive parameters of blueberries ( Vaccinium corymbosum L.), a pot experiment was conducted in three consecutive seasons in a sandy soil of south-central Chile using ‘Corona’, ‘Legacy’ and ‘Liberty’. The following fertilizers were evaluated: compost (CM), Purely Grow (PG), Purely Lysine (PL), Fertil (F), blood meal (BM), lupine meal (LM), along with a control treatment without fertilization (C) and two conventional treatments with urea (CF) and sodium nitrate (S). Results indicate that vegetative growth and leaf N concentration prior to senescence were different among cultivars in the three evaluated seasons. The highest leaf N concentration was recorded in ‘Corona’ followed by ‘Legacy’ and ‘Liberty’ while levels tended to increase in the seasons. Quick-release N sources had greater effects on these parameters but with differences among cultivars. Fruit yield and weight were higher in ‘Corona’ followed by ‘Legacy’ and ‘Liberty’. Fruit yield was generally higher when using LM and F and showed no effect on fruit weight. Leaf chlorophyll content was higher in ‘Corona’ followed by ‘Legacy’ and ‘Liberty’, which increased when using CF, LM, BM, and PG. Finally, the organic fertilizer and blueberry cultivar that obtained the highest values for most of the evaluated parameters were LM and Corona, respectively.

Stoichiometry dependence of the evolution of the irradiated-induced defect clusters in lanthanum-doped ceria

To study the stoichiometry dependence of irradiation e ects in fluorite-type mixed oxide nuclear fuel (UPuO2), ion implantation in La doped ceria was used. Cerium dioxide single crystals with 0 mol%, 5 mol% and 25 mol% La concentration were irradiated with 1 MeV Kr ions at 800 C. In-situ transmission electron microscope (TEM) was utilized to observe the the damage process and defects created by the ion beam irradiation. Dislocation loops were observed after irradiation and were determined to be on {111} planes, but not on {220} or {200} planes. Ab substantial difference in the average size of dislocation loops for 0 %, 5% and 25% cases was observed at several doses.The growth rate of dislocation loops and the oxygen vacancy di usivity were found to be inversely correlated.

Release currents of IP₃ receptor channel clusters and concentration profiles

We simulate currents and concentration profiles generated by Ca2+ release from the endoplasmic reticulum (ER) to the cytosol through IP3 receptor channel clusters. Clusters are described as conducting pores in the lumenal membrane with a diameter from 6 nm to 36 nm. The endoplasmic reticulum is modeled as a disc with a radius of 1–12 mm and an inner height of 28 nm. We adapt the dependence of the currents on the trans Ca2+ concentration (intralumenal) measured in lipid bilayer experiments to the cellular geometry. Simulated currents are compared with signal mass measurements in Xenopus oocytes. We find that release currents depend linearly on the concentration of free Ca2+ in the lumen. The release current is approximately proportional to the square root of the number of open channels in a cluster. Cytosolic concentrations at the location of the cluster range from 25 μM to 170 μM. Concentration increase due to puffs in a distance of a few micrometers from the puff site is found to be in the nanomolar range. Release currents decay biexponentially with timescales of < 1 s and a few seconds. Concentration profiles decay with timescales of 0.125–0.250 s upon termination of release.

Herramienta para la representación 3D, usando WebGL, de clusters de supercomputación

Este Trabajo de Fin de Grado constituye el primero en una línea de Trabajos con un objetivo común: la creación de una aplicación o conjunto de aplicaciones que apoye a la administración de un cluster de supercomputación mediante una representación en tres dimensiones del mismo accesible desde un navegador. Esta aplicación deberá ser de fácil manejo para el personal que haga uso de ella, que recibirá información procedente de distintas fuentes sobre el estado de cada uno de los dispositivos del cluster. Concretamente, este primer Trabajo se centra en la representación gráfica del cluster mediante WebGL, el estándar para renderizado 3D en navegadores basado en OpenGL, tomando como modelo de desarrollo el SCBI (Centro de Supercomputación y Bioinnovación) de la Universidad de Málaga. Para ello, se apoyará en la creación de una herramienta con la que describir texualmente de forma intuitiva los elementos de una sala de supercomputadores y los datos asociados a los mismos. Esta descripción será modificable para adaptarse a las necesidades del administrador de los datos.

Benchmarking Density Functional Based Tight-Binding for Silver and Gold Materials: From Small Clusters to Bulk

International audience

Reactive clusters on a membrane

We investigate the reaction dynamics of diffusive molecules with immobile binding partners. The fixed reactants build clusters that comprise just a few tens of molecules, which leads to small cluster sizes. These molecules participate in the reaction only if they are activated. The dynamics of activation is mapped to a time-dependent size of an active region within the cluster. We focus on the deterministic description of the dynamics of a single cluster. The spatial setup accounts for one of the most important determinants of the dynamics of a cluster, i.e. diffusional transport of reaction partners toward or away from the active region of the cluster. We provide numerical and analytical evidence that diffusion influences decisively the dynamic regimes of the reactions. The application of our methods to intracellular Ca²⁺ dynamics shows that large local concentrations saturate the Ca²⁺ feedback to the channel state control. That eliminates oscillations depending on this feedback.

The connection between the university and the productive sector: technological transference

This paper analyzes the process of technological transfer from the university to the industry, firstly through a brief overview of the innovation role, and particularly of universities, according to various economic theories (Neoclassical Theory, Schumpeter and his followers, and Marxism) -- Next, the Bologna Process, a specific European case of technology transfer, is considered from empirical sources, official speeches, regulations and official documents -- Finally, the general trend of explicit relation in Argentina between the university and the productive sector is briefly analyzed from certain empirical evidence, official speeches and policies, in order to guide the understanding of this process in Latin America -- The main conclusion of the study aims to consider technological transfer as intrinsic and necessary for the contemporary capitalism

Stable spike clusters for the one-dimensional Gierer-Meinhardt system

We consider the Gierer-Meinhardt system with precursor inhomogeneity in a one-dimensional interval. A spike cluster is the combination of several spikes which all approach the same point in the singular limit of small activator diffusivity. We rigorously prove the existence of a steady-state spike cluster consisting of N spikes near a non-degenerate local minimum point of the smooth inhomogeneity, where N is an arbitrary positive integer. Further, we show that this solution is linearly stable. We explicitly compute all eigenvalues, both large (of order O(1)) and small (of order o(1)). The main features of studying the Gierer-Meinhardt system in this setting are as follows: (i) it is biologically relevant since it models a hierarchical process (pattern formation of small-scale structures induced by a pre-existing large-scale inhomogeneity), (ii) it contains three different spatial scales two of which are small. (iii) all the expressions can be made explicit and often have a particularly simple form.

As dinâmicas dos clusters como potenciadoras da competitividade empresarial regional : o caso do cluster hortícola do Ribatejo & Oeste : análise comparativa com Almeria (Espanha)

Mestrado em Gestão e Estratégia Industrial

Effects of different intensity of early leaf removal on vegetative and productive activity and grape quality (cv. Nero d'Avola, Vitis vinifera)

Mestrado Vinifera Euromaster - Instituto Superior de Agronomia - UL

Local productive arrangements for biodiesel production in Brazil: Environmental assessment of small-holders integrated oleaginous crops management.

Sustainability assessments were carried out in small-holders? farms in four territories where productive arrangements have been organized for production of minor oleagi- nous crops under the Brazilian biodiesel program. The study aimed at checking local impacts of the biodiesel productive chains at the rural establishment scale, and pro- moting the environmental performance of the selected farms, henceforth proposed as sustainable management demonstration units. Assessments were carried out with the APOIA-NovoRural system, which integrates 62 objective and quantitative indicators re- lated to five sustainability dimensions: i) Landscape Ecology, ii) Environmental Quality (Atmosphere, Water and Soil), iii) Socio-cultural Values, iv) Economic Values and v) Management and Administration. The main results point out that, in general, the eco- logical dimensions of sustainability, that is, the Landscape Ecology and Atmosphere, Water, and Soil quality indicators, show adequate field conditions, seemingly not yet negatively affected by increases in chemical inputs and natural resources use predicted as important potential impacts of the agro-energy sector. The Economic Values indica- tors have been favorably influenced in the studied farms, due to a steadier demand and improved prices for the oleaginous crops. On the other hand, valuable positive conse- quences expected for favoring farmers? market insertion, such as improved Socio-cultural Values and Management & Administration indicators, are still opportunities to be ma-terialized. The Environmental Management Reports issued to the farmers, based on the presented sustainability assessment procedures, offer valuable documentation and com-munication means for consolidating the organizational influence of the local productive arrangements studied. These productive arrangements were shown to be determinant for the selection of crop associations and diversification, as well as for the provision of technical assistance and the stabilization of demand - conditions that promote value aggregation and income improvements, favoring small-holders? insertion in the market. More importantly, these locally organized productive arrangements have been shown to strongly influence the valorization of natural resources and environmental assets, which are fundamental if sustainable rural development is to take place under the emerging agro-energy scenario.