Intra-group Light in Hickson Compact Groups

We have analyzed the intra-group light component of 3 Hickson Compact Groups (HCG 79, HCG 88 and HCG 95) with detections in two of them: HCG 79, with $46\pm11$ of the total $B$ band luminosity and HCG 95 with $11\pm26$. HCG 88 had no component detected. This component is presumably due to tidally stripped stellar material trapped in the group potential and represents an efficient tool to determine the stage of dynamical evolution and to map its gravitational potential. To detect this low surface brightness structure we have applied the wavelet technique OV\_WAV, which separates the different components of the image according to their spatial characteristic sizes.Comment: Small update on the associated institutions lis

Stability and nonlinear adjustment of vortices in Keplerian flows

We investigate the stability, nonlinear development and equilibrium structure of vortices in a background shearing Keplerian flow. We make use of high-resolution global two-dimensional compressible hydrodynamic simulations. We introduce the concept of nonlinear adjustment to describe the transition of unbalanced vortical fields to a long-lived configuration. We discuss the conditions under which vortical perturbations evolve into long-lived persistent structures and we describe the properties of these equilibrium vortices. The properties of equilibrium vortices appear to be independent from the initial conditions and depend only on the local disk parameters. In particular we find that the ratio of the vortex size to the local disk scale height increases with the decrease of the sound speed, reaching values well above the unity. The process of spiral density wave generation by the vortex, discussed in our previous work, appear to maintain its efficiency also at nonlinear amplitudes and we observe the formation of spiral shocks attached to the vortex. The shocks may have important consequences on the long term vortex evolution and possibly on the global disk dynamics. Our study strengthens the arguments in favor of anticyclonic vortices as the candidates for the promotion of planetary formation. Hydrodynamic shocks that are an intrinsic property of persistent vortices in compressible Keplerian flows are an important contributor to the overall balance. These shocks support vortices against viscous dissipation by generating local potential vorticity and should be responsible for the eventual fate of the persistent anticyclonic vortices. Numerical codes have be able to resolve shock waves to describe the vortex dynamics correctly.Comment: 12 pages, 10 figure

Family firm network strategies in regional clusters: evidence from Italy

Plain English SummaryFamily firms are key in supporting local development, especially in regional clusters. However, while it is well established that their strategies differ from other (non-family) firms, it is still unclear what is their networking behaviour for supporting knowledge exchange-and thus innovation. This paper provides an empirical overview of this phenomenon, by analyzing an Italian case study: the Parabiago footwear cluster. The results show that (a) family firms are more proactive in establishing network relationships; (b) family firms tend to exchange knowledge with other family firms, while non-family firms do not show the same homophilous approach. Overall, this indicates that policies for clusters need to balance support for distinct business types and recognize the familiness characteristics of regional productive structures.Knowledge networks in regional clusters are fundamental to support innovation and local development. Within clusters, family firms are key in creating business opportunities and supporting the establishment of inter-organizational networks. Yet, their role within regional clusters for knowledge transfers is still not well understood, especially in comparison with non-family firms. This paper applies Exponential Random Graph Models (ERGMs) to network data collected from the Parabiago cluster, one of the most important Italian footwear clusters, to contribute to a better understanding of the network strategies of family firms. We identify distinct network strategies associated with the cluster firms, accounting for different knowledge exchange types: technological, market, and managerial. In our modelling, we control for firm-level attributes and dyadic-level attributes, such as geographical distance and cognitive proximity between cluster firms. Our results suggest that the proneness of family firms to grow networks is highly robust relative to non-family firm relationships, irrespective of knowledge types being exchanged. Moreover, family firms tend to establish connections with other family firms, showing the presence of homophily in their networking approach; however, non-family firms are rather different, since they do not have the same homophilous approach when it comes to exchange knowledge with other non-family firms. These results indicate that the nature of ownership is driving knowledge exchange differences. This key feature of family-only relationships in clusters may help managers and policymakers in devising more effective and targeted cluster strategies.Peer reviewe

Plla funcionalizado com líquido iônico imidazólico para a obtenção de bionanocompósitos inovadores com grafeno

O PLLA é um poliéster biodegradável produzido a partir de fontes renováveis que tem recebido atenção nas pesquisas de polímeros biodegradáveis alternativos, uma vez que foi aprovado pelo Food and Drug Administration (FDA) para aplicações médicas. Neste trabalho foram produzidos bionanocompósitos de grafeno a base de PLLA funcionalizado com líquido iônico (PLLA-LI), a fim de verificar as propriedades mecânicas e térmicas e se os mesmos apresentavam atividade antibiofilme. Para a produção dos filmes foi utilizada a técnica de solvent casting. Foram produzidas amostras de PLLA-LI puros, de blendas de PLLA-LI em PLLA comercial tal qual com adição de diferentes percentuais de óxido de grafeno reduzido. Os filmes foram caracterizados por TGA, DMA, ângulo de contato da água e MEV. Nesses filmes também foram realizados ensaios de Menor Concentração Antibiofilme frente à cepas de Candida sp. Os filmes de PLLA-LI mostraram aumento na resistência térmica em até 116%. Com a adição de grafeno, propriedades mecânicas como o módulo de armazenamento melhoraram em até 106% e um aumento de até 25,8° do ângulo de contato da água em relação ao PLLA comercial foi verificado. Nas análises de MEV, foi possível verificar o encapsulamento do polímero com controle morfológico para o bionanocompósito de PLLA-LI com óxido de grafeno reduzido. Além disso, as amostras tratadas com PLLA-LI apresentaram atividade antibiofilme. Os resultados aqui apresentados levam a concluir que existe um potencial de aplicação desse novo tipo de material em diversas áreas do conhecimento, como por exemplo a área médicas.PLLA is a biodegradable polyester produced from renewable sources and has received attention in alternative biodegradable polymers researches once it was approved by the Food and Drug Administration (FDA) for medical applications. Bionanocomposites of functionalized PLLA (PLLA-LI) with graphene were produced in order to verify antibiofilm activity and mechanical and thermal properties. Solvent casting technique was used to produce the films. Samples of pure commercial PLLA, PLLA-LI, PLLA-LI blends in commercial PLLA and also with the addition of different percentages of reduced graphene oxide were produced. The films were characterized by TGA, DMA, water contact angle and SEM. A Minor Antibiofilm Concentration test was performed against the strains of Candida sp. PLLA-LI films showed an increase in thermal resistance up to 116%. With graphene addition, mechanical properties such as the storage modulus improved by up to 106% and the water contact angle increased by 25.8° relative to commercial PLLA. SEM results showed polymer encapsulation with controlled morphology for the PLLA-LI bionanocomposite with reduced graphene oxide. In addition, samples treated with PLLA-LI showed antibiofilm activity against Candida ssp strains. The results presented here lead to the conclusion that there is a potential application of this new type of material in several areas of knowledge, such as the biomedical sciences

Globular Clusters around Galaxies in Groups

We have obtained deep photometry of NGC 1199 (in HCG 22) and NGC 6868 (in the Telescopium group). Both galaxies are the optically brightest galaxies of their groups. Our analysis of B and R images taken with the Keck II and the VLT/ESO telescopes, detected a population of globular clusters around both galaxies, with total specific frequencies S_N=1.7\pm0.6 for NGC 1199 and S_N = 1.3\pm0.6 for NGC 6868. The color distributions of the globular cluster systems shows bimodal peaks centered at (B-R)_0 = 1.13\pm0.10 and 1.42\pm0.10 (NGC 1199) and (B-R)_0=1.12\pm0.10 and 1.42\pm0.10 (NGC 6868).Comment: 3 pages, 1 figure. To appear in the proceedings of IAU Symp. 207, "Extragalactic Star Clusters", eds. E. Grebel, D. Geisler, D. Minnit

Commitment of chondrogenic precursors of the avian scapula takes place after epithelial-mesenchymal transition of the dermomyotome

<p>Abstract</p> <p>Background</p> <p>Cells of the epithelially organised dermomyotome are traditionally believed to give rise to skeletal muscle and dermis. We have previously shown that the dermomyotome can undergo epithelial-mesenchymal transition (EMT) and give rise to chondrogenic cells, which go on to form the scapula blade in birds. At present we have little understanding regarding the issue of when the chondrogenic fate of dermomyotomal cells is determined. Using quail-chick grafting experiments, we investigated whether scapula precursor cells are committed to a chondrogenic fate while in an epithelial state or whether commitment is established after EMT.</p> <p>Results</p> <p>We show that the hypaxial dermomyotome, which normally forms the scapula, does not generate cartilaginous tissue after it is grafted to the epaxial domain. In contrast engraftment of the epaxial dermomyotome to the hypaxial domain gives rise to scapula-like cartilage. However, the hypaxial sub-ectodermal mesenchyme (SEM), which originates from the hypaxial dermomyotome after EMT, generates cartilaginous elements in the epaxial domain, whereas in reciprocal grafting experiments, the epaxial SEM cannot form cartilage in the hypaxial domain.</p> <p>Conclusions</p> <p>We suggest that the epithelial cells of the dermomyotome are not committed to the chondrogenic lineage. Commitment to this lineage occurs after it has undergone EMT to form the sub-ectodermal mesenchyme.</p

Water-Vapour Monitoring from Ground-Based GNSS Observations in Northwestern Argentina

The Central Andes in northwestern Argentina are characterized by steep topographic and climatic gradients. The humid foreland areas at 1 km asl elevation rapidly rise to over 5 km in the eastern Cordillera, and they form an orographic rainfall barrier on the eastern windward side. This topographic setting combined with seasonal moisture transport through the South American monsoon system leads to intense rainstorms with cascading effects such as landsliding and flooding. In order to better quantify the dynamics of water vapour transport, we use high-temporal-resolution global navigation satellite system (GNSS) remote sensing techniques. We are particularly interested in better understanding the dynamics of high-magnitude storms with high water vapour amounts that have destructive effects on human infrastructure. We used an existing GNSS station network with 12 years of time series data, and we installed two new ground stations along the climatic gradient and collected GNSS time series data for three years. For several stations we calculated the GNSS signal delay gradient to determine water vapour transport direction. Our statistical analysis combines in situ rainfall measurements and ERA5 reanalysis data to reveal the water vapour transport mechanism for the study area. The results show a strong relationship between altitude and the water vapour content, as well as between the transportation pathways and the topography.Fil: Antonoglou, Nikolaos. German Research Centre for Geosciences; Alemania. Universitat Potsdam; AlemaniaFil: Balidakis, Kyriakos. German Research Centre for Geosciences; AlemaniaFil: Wickert, Jens. Technishe Universitat Berlin; Alemania. German Research Centre for Geosciences; AlemaniaFil: Dick, Galina. German Research Centre for Geosciences; AlemaniaFil: de la Torre, Alejandro. Universidad Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bookhagen, Bodo. Universitat Potsdam; Alemani

Vorticity production through rotation, shear and baroclinicity

In the absence of rotation and shear, and under the assumption of constant temperature or specific entropy, purely potential forcing by localized expansion waves is known to produce irrotational flows that have no vorticity. Here we study the production of vorticity under idealized conditions when there is rotation, shear, or baroclinicity, to address the problem of vorticity generation in the interstellar medium in a systematic fashion. We use three-dimensional periodic box numerical simulations to investigate the various effects in isolation. We find that for slow rotation, vorticity production in an isothermal gas is small in the sense that the ratio of the root-mean-square values of vorticity and velocity is small compared with the wavenumber of the energy-carrying motions. For Coriolis numbers above a certain level, vorticity production saturates at a value where the aforementioned ratio becomes comparable with the wavenumber of the energy-carrying motions. Shear also raises the vorticity production, but no saturation is found. When the assumption of isothermality is dropped, there is significant vorticity production by the baroclinic term once the turbulence becomes supersonic. In galaxies, shear and rotation are estimated to be insufficient to produce significant amounts of vorticity, leaving therefore only the baroclinic term as the most favorable candidate. We also demonstrate vorticity production visually as a result of colliding shock fronts.Comment: 9 pages, 10 figures, Accepted for publication in A&