Large fluctuations of the nonlinearities in isotropic turbulence. Anisotropic filtering analysis

Using a Navier–Stokes isotropic turbulent field numerically simulated in a box with a discretization of 10243 (Biferale et al., 2005), we show that the probability of having a stretching–tilting larger than a few times the local enstrophy is low. By using an anisotropic kind of filter in the Fourier space, where wavenumbers that have at least one component below a threshold or inside a range are removed, we analyze these survival statistics when the large, the small inertial or the small inertial and dissipation scales are filtered out. By considering a flow obtained by randomizing the phases of the Fourier modes, and applying our filtering techniques, we identified clearly the properties attributable to turbulence. It can be observed that, in the unfiltered isotropic Navier–Stokes field, the probability of the ratio (|ω·∇U|/|ω|2) being higher than a given threshold is higher than in the fields where the large scales were filtered out. At the same time, it is lower than in the fields where the small inertial and dissipation range of scales is filtered out. This is basically due to the suppression of compact structures in the ranges that have been filtered in different ways. The partial removal of the background of filaments and sheets does not have a first order effect on these statistics. These results are discussed in the light of a hypothesized relation between vortical filaments, sheets and blobs in physical space and in Fourier space. The study in fact can be viewed as a kind of test for this idea and tries to highlight its limits. We conclude that a qualitative relation in physical space and in Fourier space can be supposed to exist for blobs only. That is for the near isotropic structures which are sufficiently described by a single spatial scale and do not suffer from the disambiguation problem as filaments and sheets do. Information is also given on the filtering effect on statistics concerning the inclination of the strain rate tensor eigenvectors with respect to vorticity. In all filtered ranges, eigenvector 2 reduces its alignment, while eigenvector 3 reduces its misalignment. All filters increase the gap between the most extensional eigenvalue ⟨λ1⟩ and the intermediate one ⟨λ2⟩ and the gap between this last ⟨λ2⟩ and the contractile eigenvalue ⟨λ3⟩. When the large scales are missing, the modulus of the eigenvalue 1 becomes nearly equal to that of the eigenvalue 3, similarly to the modulus of the associated components of the enstrophy production

Romanesque and territory. The construction materials of Sardinian medieval churches: new approaches to the valorization, conservation and restoration

This paper is intended to illustrate a multidisciplinary research project devoted to the study of the constructive materials of the Romanesque churches in Sardinia during the “Giudicati” period (11th -13th centuries). The project focuses on the relationship between a selection of monuments and their territory, both from a historical-architectural perspective and from a more modern perspective addressing future restoration works. The methodologies of the traditional art-historical research (study of bibliographic, epigraphic and archival sources, formal reading of artifacts) are flanked by new technologies: digital surveys executed with a 3D laser-scanner, analyses of the materials (stones, mortars, bricks) with different instrumental methods: X-ray fluorescence (XRF) and inductively coupled mass spectrometry (ICP-MS) for chemical composition, X-ray diffractometer (XRD) to determine the alteration phases (e.g., soluble salts), optical microscopy and electronic (SEM) to study textures, mineral assemblages and microstructures, termogravimetric/differential scanning, calorimetric analysis (TG/DTA) for the composition of the binder mortars. This multidisciplinary approach allows the achieving of important results in an archaeometric context: 1) from a historical point of view, with the possible identification of ancient traffics, trade routes, sources of raw materials, construction phases, wall textures; 2) from a conservative point of view, by studying chemical and physical weathering processes of stone materials compatible for replacement in case of future restoration works. Sardinian Romanesque architectural heritage is particularly remarkable: about 200 churches of different types and sizes, with the almost exclusive use of cut stones. Bi- or poly-chromy, deriving from the use of different building materials, characterizes many of these monuments, becoming also a vehicle for political and cultural meanings. The paper will present some case studies aimed to illustrate the progress of the project and the results achieved

Transmission line parameters estimation in the presence of realistic PMU measurement error models

Proposals have been presented in literature to estimate line parameters and monitor their changes. Syn-chrophasor measurements from phasor measurement units (PMUs) have appeared as a possible breakthrough for accurate estimation. However, few methods consider a realistic measurement chain including PMUs and instrument transformers and their systematic and random error contributions. This paper proposes an improved method to simultaneously estimate line parameters and systematic measurement errors on multiple network lines. The algorithm is designed to deal with realistic PMU measurement errors and, in particular, with phase -angle errors caused by common time-base errors on multiple PMU channels. The impact of PMU measurement errors is investigated to achieve a comprehensive view of the performance under realistic conditions. The results obtained on an IEEE test network prove the advantages of the proposed method with respect to other recent methods and its robustness in the presence of mismatches in the error model

Pyroclastic Stones as Building Materials in Medieval Romanesque Architecture of Sardinia (Italy): Chemical-Physical Features of Rocks and Associated Alterations

The paper discusses the chemical-physical-petrographic features and decay processes of San Nicola Church (11th−14th century) building materials, one of the most representative Medieval Churches in Sardinia, stylistically attributable to the Romanesque architecture. The monument was built up into two stages and shows a characteristic size uniformity of the ashlars. The masonry is mainly made up of rhyodacitic pyroclastites belonging to the Sardinian Eocene-Miocene magmatic phase (38–15 My). These volcanic rocks were widely used in Medieval architecture for the excellent workability, but its minero-petrographic features greatly favor the decay, due to the action of chemical-physical alteration processes. Although the alteration degree and macroscopic forms of decay vary from zone to zone in the monument, according to the different compositional features of the volcanic stones, weathering and exposure condition, the pyroclastic rocks are generally affected by greater alteration than other igneous lithotypes, due to their petrographic-volcanological characteristics (e.g., low-medium welding grade, medium-high porosity). The results concerning mineralogical and petrographic features, respectively, carried out by the application of X-Ray Powder Diffraction (XRPD), Optical Microscope (OM), and Scanning Electron Microscope (SEM) techniques, both on fresh building rocks and associated alterations, are here presented and discussed. Furthermore, the relationships between fresh pyroclastites and alteration processes affecting these rocks will be discussed

The invasion of abandoned fields by a major alien tree filters understory plant traits in novel forest ecosystems

The abandonment of agricultural use is a common driver of spontaneous reforestation by alien trees. The N-fixing black locust (Robinia pseudoacacia L.) is a major alien invader of old fields in Europe. Here we show that canopy dominance by this tree may filter the frequency distribution of plant functional traits in the understory of secondary woodlands. Higher soil C/N ratio and available P are associated with black locust stands, while higher soil phenols associate with native tree stands. These environmental effects result in differences in understory flowering periods, reproduction types and life forms. Our findings emphasize the effect of a major alien tree on functional plant trait composition in the early stages of spontaneous reforestation of abandoned lands, implying the development of a novel forest ecosystem on a large geographical scale.Peer reviewe

Heterogeneity in Preferences towards Complexity

We analyze lottery-choice data in a way that separately estimates the effects of risk aversion and complexity aversion. Complexity is represented by the number of different outcomes in the lottery. A finite mixture random effects model is estimated which assumes that a proportion of the population are complexity-neutral. We find that around 33% of the population are complexity-neutral, around 50% complexity-averse, and the remaining 17% are complexity-loving. Subjects who do react to complexity appear to have a bias towards complexity aversion at the start of the experiment, but complexity aversion reduces with experience, to the extent that the average subject is (almost) complexity-neutral by the end of the experiment. Complexity aversion is found to increase with age and to be higher for non-UK students than for UK students. We also find some evidence that, when evaluating complex lotteries, subjects perceive probabilities in accordance with Prospective Reference Theory

Inattentive Consumers in Markets for Services

In an experiment on markets for services, we find that consumers are likely to stick to default tariffs and achieve suboptimal outcomes. We find that inattention to the task of choosing a better tariff is likely to be a substantial problem in addition to any task and tariff complexity effect. The institutional setup on which we primarily model our experiment is the UK electricity and gas markets, and our conclusion is that the new measures by the UK regulator Ofgem to improve consumer outcomes are likely to be of limited impact

Correlation between cephalometric variables and obstructive sleep apnoea severity in children.

Aim Alterations in craniofacial growth have been associated with obstructive sleep apnoea in children. The main objectives of this study were to analyse the correlation between cephalometric variables and Obstructive Apnea/Hypopnea Index (OAHI) in order to investigate if craniofacial features may influence the severity of obstructive sleep apnoea and to study the correlation between upper nasopharyngeal width and maxillomandibular skeletal discrepancy in sagittal and vertical plane. Materials and methods Study Design: Correlations between cephalometric variables and obstructive sleep apnoea/hypopnea index and between upper airways space and maxillomandibular skeletal discrepancy were investigated. Forty-seven children with obstructive sleep apnoea diagnosed by overnight sleep study (polysomnography) underwent a lateral radiograph, orthodontic and ear-nose-throat examinations. Cephalometric analysis according to Kirjavainen has been performed to define skeletal and upper airways variables. Statistics: Spearman’s correlation analysis was performed between OAHI and all cephalometric variables. Pearson’s correlation analysis was performed between cephalometric variables of upper airway space and cephalometric variables related to maxillomandibular discrepancy. Chi-square test was used to compare occlusal features with adenoidal and tonsillar hypertrophy. Kruskal-Wallis rank test was used to compare OAHI with occlusal variables and adenotonsillar hypertrophy. Results The results show a positive correlation between OAHI and maxillomandibular discrepancy measured by ANB angle (rho=0.32; p=0.023). A significant correlation was found between upper nasopharyngeal width and vertical maxillomandibular skeletal discrepancy: 1) ad1-PNS were correlated to Mandibular Plane/SellaNasion angle (r=-0.36; p=0.012), Palatal Plane/Mandibular Plane angle (r=-0.39; p=0.007), and Posterior-Anterior Facial Height % (r=0.29; p=0.045); 2) ad2-PNS was correlated to Palatal Plane/Mandibular Plane angle (r=-0.39; p=0.007). No statistically significant differences were found in non-parametric tests between OAHI and occlusal variables or adenoidal and tonsillar hypertrophy. Conclusions The present study shows a significant correlation between maxillomandibular discrepancy and the severity of OSA. Moreover, the reduction of nasopharyngeal width was correlated to maxillomandibular hyperdivergent growth pattern. These results support the presence of a correlation between sleep-disordered breathing and craniofacial features even if the cause-effect relation is still unclear. Based on these evidences, we suggest the importance of orthodontic evaluation in the management of paediatric OSA

Defective dystrophic thymus determines degenerative changes in skeletal muscle.

In Duchenne muscular dystrophy (DMD), sarcolemma fragility and myofiber necrosis produce cellular debris that attract inflammatory cells. Macrophages and T-lymphocytes infiltrate muscles in response to damage-associated molecular pattern signalling and the release of TNF-α, TGF-β and interleukins prevent skeletal muscle improvement from the inflammation. This immunological scenario was extended by the discovery of a specific response to muscle antigens and a role for regulatory T cells (Tregs) in muscle regeneration. Normally, autoimmunity is avoided by autoreactive T-lymphocyte deletion within thymus, while in the periphery Tregs monitor effector T-cells escaping from central regulatory control. Here, we report impairment of thymus architecture of mdx mice together with decreased expression of ghrelin, autophagy dysfunction and AIRE down-regulation. Transplantation of dystrophic thymus in recipient nude mice determine the up-regulation of inflammatory/fibrotic markers, marked metabolic breakdown that leads to muscle atrophy and loss of force. These results indicate that involution of dystrophic thymus exacerbates muscular dystrophy by altering central immune tolerance

On reminder effects, drop-outs and dominance: evidence from an online experiment on charitable giving

We present the results of an experiment that (a) shows the usefulness of screening out drop-outs and (b) tests whether different methods of payment and reminder intervals affect charitable giving. Following a lab session, participants could make online donations to charity for a total duration of three months. Our procedure justifying the exclusion of drop-outs consists in requiring participants to collect payments in person flexibly and as known in advance and as highlighted to them later. Our interpretation is that participants who failed to collect their positive payments under these circumstances are likely not to satisfy dominance. If we restrict the sample to subjects who did not drop out, but not otherwise, reminders significantly increase the overall amount of charitable giving. We also find that weekly reminders are no more effective than monthly reminders in increasing charitable giving, and that, in our three months duration experiment, standing orders do not increase giving relative to one-off donations