Vibration and buckling of open TWBs with local weakening

Free vibration and Ljapounov stability of compressed open thin-walled beams with a cross-section reduction are studied by a in-house finite differences numerical code, based on a refined direct beam model and allowing for investigating elastic stability of non-trivial equilibrium paths in a dynamic setting. The benchmark is a beam with doubly symmetric cross-section and non-zero warping rigidity, under free, semi-, and fully restrained warping at its ends. In all cases, the results of the direct model are compared to finite element and/or experimental ones. The reduction in the cross-section rigidity induces a weakening that may model a local damage; thus, the present investigation may be useful with an outlook to damage monitoring and identification

Perturbation damage indicators based on complex modes

The papers focusing on dynamic identification of structural damages usually rely on the comparison of two or more responses of the structure; the measure of damage is related to the differences of the vibration signals. Almost all literature methods assume damping proportionality to mass and stiffness; however, this is acceptable for new, undamaged structures, but not for existing, potentially damaged structures, especially when localised damages occur. It is well-known that in non-proportionally damped systems the modes are no longer the same of the undamped system: thus, some authors proposed to use modal complexity as a damage indicator. This contribution presents a perturbation approach that can easily reveal such a modal complexity

Genetic Toolkit for Assessment and Prediction of Population-Level Impacts of Bridge Construction on Birds

Recent studies have highlighted alarming rates of declines in bird populations across the country. The State of California is home to over 650 resident and migrant avian species. Legislation for protecting these species has existed for over a century now, yet tools for identifying populations and understanding seasonal movement remain limited. Recently, genetic and genomic tools have provided a method for understanding population structure, allowing for more informed delineation of management units. The goal of this project was to create a genetic toolkit for identifying breeding populations and assigning individuals to those populations. Ultimately, such tools could be used to assess population-level impacts when there are conflicts with birds at infrastructure construction sites. As a test case, we sequenced entire genomes for 40 individual Anna’s hummingbirds (Calypte anna) from across the state. Based on this initial data, we found low levels of differentiation between sampled locations, suggesting that C. anna in California are not subdivided into different population units. However, there was a weak signal of geography suggesting there may be localized genetic differences in a small proportion of the genome. Follow-up work will focus on a broader sampling across the state of California to clarify any possible population subdivision or geographical patterns of differentiation.View the NCST Project Webpag

Indicatori della lavorazione tessile nel Veneto preromano

Among the grave goods of the ancient Veneto burials, ceramic spindle whorls, reels and counterweights are quite common: they are related to the female world, of which the textile manufacturing was an important element. Some years ago, in a paper written for the catalougue of the exhibition Le ore e I giorni delle donne, Verucchio 2007, we started an analysis aimed at recognizing the specific indicators of weaving, such as distaffs, spindles, thread spacers, needles, buttons, along with the recently discovered weaving tablets from Este. The goal of that work was to understand the various levels of specialization involved in the different phases of the production process. We discussed some tool associations that could be considered as “toolkits”, along with some clear diachronic changes in these sets. In this paper we continued this analysis by approaching old and new data from a numerical and ponderal point of view, in order to better understand the specific function of some classes of artifacts, and be able to make hypoteses about the “invisible” tools (wooden spindles, typology and typometry of the looms…). Furthermore, a complete reconstruction of the textiles production process could help us understanding the change (from an individual, domestic activity to a large-scale production) the textile manufacturing underwent during the 1st millennium BC

Production of micropropagated melon plantlets adapted to saline environment

An experiment was carried out to evaluate the behaviour on salt stress induced by sodium chloride of two melon clones obtained from micropropagation. Since arbuscular mycorrhizal (AM) fungi seem to increase salt tolerance in some crops, at acclimatisation melon plantlets were mycorrhizal with an AM fungus. The root systems of both mycorrhizal and non mycorrhizal plants were exposed to increasing salt concentrations and then placed in distilled water to study the wilting response and the recovery of plants. Observations were made on several morphological parameters, in particular to verify the modification of root system morphology caused by AM fungus, as demonstrated already by several studies. The analysis of infected roots was carried out following Phillips and Hayman's protocol (1970). Afterwards, the specimen was read using an optical microscope

Biobanking of vegetable genetic resources by in vitro conservation and cryopreservation

Today, application of in vitro culture by means of slow growth storage of shoot cultures and cryopreservation of organs, tissues and cells in liquid nitrogen presents a remarkable strategic tool to support medium- and long-term conservation of plant genetic resources. Over the last 30 years, considerable progresses have been made in the development of both methods that are currently considered as ex situ conservation strategies, complementary to traditional seed banks and in-field clonal collections. Efficient protocols were developed for the conservation of a large number of crops, including strategically-important vegetables, such as garlic, artichoke, asparagus, cassava, Jerusalem artichoke, mint, potato, sweet potato, chicory, taro, thyme and yam. As a consequence, more than 45,000 accessions of vegetable crops are maintained in 22 genetic resources conservation centers (biobanks), located in 16 countries and 6 continents (Europe, Asia, Africa, Oceania, North and South America). Approximately 4/5 of these accessions are maintained in vitro by means of slow growth storage of shoot cultures, but cryopreservation is also constantly growing, with almost 8300 vegetable accessions being stored in liquid nitrogen at − 196 °C

AGN feedback with the Square Kilometer Array (SKA) and implications for cluster physics and cosmology

AGN feedback is regarded as an important non-gravitational process in galaxy clusters, providing useful constraints on large-scale structure formation. It modifies the structure and energetics of the intra-cluster medium (ICM) and hence its understanding is crucially needed in order to use clusters as high precision cosmological probes. In this context, particularly keeping in mind the upcoming high quality radio data expected from radio surveys like SKA with its higher sensitivity, high spatial and spectral resolutions, we review our current understanding of AGN feedback, its cosmological implications and the impact that SKA can have in revolutionizing our understanding of AGN feedback in large-scale structures. Recent developments regarding the AGN outbursts and its possible contribution to excess entropy in the hot atmospheres of groups and clusters, its correlation with the feedback energy in ICM, quenching of cooling flows and the possible connection between cool core clusters and radio mini-halos, are discussed. We describe current major issues regarding modeling of AGN feedback and its impact on the surrounding medium. With regard to the future of AGN feedback studies, we examine the possible breakthroughs that can be expected from SKA observations. In the context of cluster cosmology, for example, we point out the importance of SKA observations for cluster mass calibration by noting that most of $z>1$ clusters discovered by eROSITA X-ray mission can be expected to be followed up through a 1000 hour SKA-1 mid programme. Moreover, approximately $1000$ radio mini halos and $\sim 2500$ radio halos at $z<0.6$ can be potentially detected by SKA1 and SKA2 and used as tracers of galaxy clusters and determination of cluster selection function.Comment: 14 pages, 10 figures, Review article accepted in Journal of Astrophysics and Astronomy (JOAA

The DAG1 transcription factor negatively regulates the seed-to-seedling transition in Arabidopsis acting on ABA and GA levels

BACKGROUND: In seeds, the transition from dormancy to germination is regulated by abscisic acid (ABA) and gibberellins (GAs), and involves chromatin remodelling. Particularly, the repressive mark H3K27 trimethylation (H3K27me3) has been shown to target many master regulators of this transition. DAG1 (DOF AFFECTING GERMINATION1), is a negative regulator of seed germination in Arabidopsis, and directly represses the GA biosynthetic gene GA3ox1 (gibberellin 3-β-dioxygenase 1). We set to investigate the role of DAG1 in seed dormancy and maturation with respect to epigenetic and hormonal control. RESULTS: We show that DAG1 expression is controlled at the epigenetic level through the H3K27me3 mark during the seed-to-seedling transition, and that DAG1 directly represses also the ABA catabolic gene CYP707A2; consistently, the ABA level is lower while the GA level is higher in dag1 mutant seeds. Furthermore, both DAG1 expression and protein stability are controlled by GAs. CONCLUSIONS: Our results point to DAG1 as a key player in the control of the developmental switch between seed dormancy and germination