103,852 research outputs found
AMICO-COSMOS galaxy cluster and group catalogue up to
No full textAims. We present the results of a new galaxy cluster search in the COSMOS field obtained using the Adaptive Matched Identifier of Clustered Objects (AMICO). Our aim was to produce a new cluster and group catalogue up to z = 2 by performing an innovative application of AMICO with respect to previous successful applications to wide-field surveys in terms of depth (down to r < 26.7), small area covered (∼1.69 deg2 of unmasked effective area), and redshift extent. This sample and the comparative analysis we performed with the X-rays, allowed for the calibration of mass-proxy scaling relations up to z = 2 and down to less than 1013 M⊙, and constitutes the basis for the refinement of the cluster model for future applications of AMICO, such as the analysis of upcoming Euclid data.
Methods. The AMICO algorithm is based on an optimal linear matched filter and detects clusters in photometric galaxy catalogues using galaxy location, photometric redshift and, in the simplest case, one galaxy property. We chose to use a single magnitude as the galaxy property, avoiding the explicit use of galaxy colour for the selection of clusters. We used three different magnitudes by performing three independent runs in the r-, Y-, and H-bands using both COSMOS2020 and COSMOS2015 galaxy catalogues. We created a composite visibility mask and cluster models for the signal to detect, and we estimated the noise directly from the data.
Results. We performed a matching of the catalogues resulting from the three runs and merged them to produce a final catalogue that contains 1269 and 666 candidate clusters and groups with S/N > 3.0 and > 3.5, respectively. A total of 490 candidates are detected in all three runs. Most of the detections unmatched between runs have S/N < 3.5, which can be set as a threshold for selecting a more robust sample. We assigned X-ray properties to our detections by matching the catalogue with a public X-ray selected group sample and by estimating, for unmatched detections, the X-ray properties at the location of AMICO candidates using Chandra+XMM-Newton data. There are in total 622 candidate clusters and groups with an X-ray flux estimate. This large sample of candidates with X-ray properties allowed the calibration of the scaling relations between two AMICO mass-proxies (richness and cluster amplitude) and X-ray mass and the study of their redshift dependence for the selection of the most stable photometric bands
Deep reinforcement learning for active control of a three-dimensional bluff body wake
No full textThe application of deep reinforcement learning (DRL) to train an agent capable of learning control laws for pulsed jets to manipulate the wake of a bluff body is presented and discussed. The work has been performed experimentally at a value of the Reynolds number Re similar to 10(5) adopting a single-step approach for the training of the agent. Two main aspects are targeted: first, the dimension of the state, allowing us to draw conclusions on its effect on the training of the neural network; second, the capability of the agent to learn optimal strategies aimed at maximizing more complex tasks identified with the reward. The agent is trained to learn strategies that minimize drag only or minimize drag while maximizing the power budget of the fluidic system. The results show that independently on the definition of the reward, the DRL learns forcing conditions that yield values of drag reduction that are as large as 10% when the reward is based on the drag minimization only. On the other hand, when also the power budget is accounted for, the agent learns forcing configurations that yield lower drag reduction (5%) but characterized by large values of the efficiency. A comparison between the natural and the forced conditions is carried out in terms of the pressure distribution across the model's base. The different structure of the wake that is obtained depending on the training of the agent suggests that the possible forcing configuration yielding similar values of the reward is local minima for the problem. This represents, to the authors' knowledge, the first application of a single-step DRL in an experimental framework at large values of the Reynolds number to control the wake of a three-dimensional bluff body. Published under an exclusive license by AIP Publishing
Wall bounded flows manipulation using sinusoidal riblets
No full textWe experimentally investigate the effects of microgrooves on the development of a zero pressure gradient turbulent boundary layer. Starting from the well-known streamwise aligned riblets, we look at the effect of wavy riblets, characterized by a sinusoidal pattern in the mean flow direction. We perform hot wire experiments as well as particle image velocimetry to get some insights on the effect of the sinusoidal shape on the near wall organisation of the boundary layer. The statistical analysis clearly shows that the wavy pattern has a strong influence on the near wall structure of the boundary layer. The statistical analysis performed using the VITA technique reveals that the coherent structures that characterize the turbulent boundary layer are attenuated by the geometry manipulation. Furthermore, the POD reconstructed velocity fields, measured with PIV, reveal that the manipulation tampers with the momentum exchange occurring between the near wall and the outer region of the boundary layer, hence suggesting a modified turbulence production cycle
Deciding in conditions of uncertainty: the Delphi method and its use in the formulation of guidelines
No full textThe purpose of this paper is to analyze one of the most powerful tools in the decision-making under conditions of uncertainty, the Delphi method, and to verify the related interest of scientific world, particularly, for formulation of guidelines. The method combines the expert opinion preventing biases due to institutional role, status or dominant personality. In the text we explain the methodology and the steps through which it is possible to realize the consensus; we schematized in a didactic manner all the phases for an operational approach of the reader. The search by the most diffused biomedical database (Medline) individualized 623 citations, 7 of which are guidelines (3 of remarkable importance). In conclusion, the Delphi method may be considered particularly interesting for its theoretical assumptions and it can be used as reference tool for assuming decisions in the formulation of clinical practice guidelines as objectively as possible
Seasonal changes in starch content in pistachio organs as related to crop load
No full textThe alternate bearing in pistachio (Pistacia vera L.) results from inflorescence buds abscission differentiated on current season growth during the year of heavy crop. Inflorescence bud drop has been directly correlated with the presence of fruits on 1-year shoot, and in particular with the kernel grow that acts as the major sink of nutrients. Experimental evidences suggest the involvement of competition between reproductive organs for the available resources. The annual carbohydrates storage was analysed in mature pistachio trees characterized by low, medium and high crop load (about 1, 7 and 11 kg tree-1 of dry in-shell nuts). The experiment was carried out in 2013 in a commercial pistachio orchard, using ‘Bianca’ grafted onto P. terebinthus L. in Sicily (Italy, 37°30’ Lat N). Starch concentration was measured in sample tissues of trunk wood, current-year shoot, one-year-old and two-year-old shoots throughout the season from the dormancy phase (March) until the post-harvest period (September). During dormancy, the trunk represented the main storage organ having starch concentration ranging from 60 to 120 mg g-1 of dry weight, whereas the tissues of the other organs examined showed values below 20 mg g-1 of dry weight. The deepest decrement of starch concentration after bud-break until bloom was observed in the trunk, whereas, starch concentration started increasing after the initial growth flush. The patterns of starch in the tissues varied according with the crop load; trees bearing the highest crop load (11 kg tree-1) showed a constant starch concentration during the growing season, in contrast with the trees characterized by lower crop load values. Before the onset of dormancy, starch rapidly increased in all the shoots type and in the trunk wood and no effects of tree crop load were observed
AMICO galaxy clusters in KiDS-DR3: Constraints on ΛCDM from extreme value statistics
No full textWe constrain the ΛCDM cosmological parameter σ8 by applying the extreme value statistics for galaxy cluster mass on the AMICO KiDS-DR3 catalogue. We sample the posterior distribution of the parameters by considering the likelihood of observing the largest cluster mass value in a sample of Nobs = 3644 clusters with intrinsic richness λ∗ > 20 in the redshift range z [0.10, 0.60]. We obtain, consistent within 1σ with the measurements obtained by the Planck collaboration and with previous results from cluster cosmology exploiting AMICO KiDS-DR3. The constraints could improve by applying this method to forthcoming missions, such as Euclid and LSST, which are expected to deliver thousands of distant and massive clusters
Trattamento delle salmonellosi nel pollo con Apramicina.
No full textThe efficacy of Apramycin given orally at the dose levels of 0,250 and 125 mg/l for 3 days to chicks experimentally infected with Salmonella typhimurium has been evaluated. The results show that Apramycin at dose level of 500 mg/l for 3 days was the most successeful treatment for the control of mortality and salmonella excretion
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