A simple model of wave-current interaction

The interaction between a steady current and propagating surface waves is investigated by means of a perturbation approach, which assumes small values of the wave steepness and considers current velocities of the same order of magnitude as the amplitude of the velocity oscillations induced by wave propagation. The problems, which are obtained at the different orders of approximation, are characterized by a further parameter which is the ratio between the thickness of the bottom boundary layer and the length of the waves and turns out to be even smaller than the wave steepness. However, the solution is determined from the bottom up to the free surface, without the need to split the fluid domain into a core region and viscous boundary layers. Moreover, the procedure, which is employed to solve the problems at the different orders of approximation, reduces them to one-dimensional problems. Therefore, the solution for arbitrary angles between the direction of the steady current and that of wave propagation can be easily obtained. The theoretical results are compared with experimental measurements; the fair agreement found between the model results and the laboratory measurements supports the model findings

Note di Meccanica dei Fluidi

Queste note sono state scritte per fornire un testo di riferimento per approfondire gli argomenti trattati durante i corsi di Idrodinamica e Meccanica dei Fluidi off erti agli studenti delle lauree magistrali in Ingegneria Navale, Civile e Ambientale attive presso la Scuola Politecnica. Tuttavia anche gli studenti di altri corsi di laurea magistrale possono trovarle utili per la loro formazione. Partendo dai principi fondamentali della fi sica, nelle note vengono ricavate le equazioni puntuali che descrivono la dinamica dei fl uidi. Successivamente vengono descritte alcune soluzioni esatte del problema del moto di un fl uido e gli approcci che sono utilizzati per determinare in forma approssimata il campo di moto, quando la complessit\ue0 del problema ne impedisce la soluzione in forma chiusa. In particolare vengono esaminati i moti caratterizzati da bassi e alti valori del numero di Reynolds. In quest\u2019ultimo caso vengono descritti il modello di fl uido ideale e quello di moto irrotazionale insieme alla teoria dello strato limite. L\u2019ultima parte delle note \ue8 dedicata ai moti turbolenti, anche se la vastit\ue0 di questo argomento ne impedisce una trattazione approfondita.These notes were written to provide a reference text for the students of the master degrees in Naval, Civil and Environmental Engineering of the Polytechnic School of the University of Genoa, who are interested in learning more about the topics covered in the courses of Hydrodynamics and Fluid Mechanics. However, also students of other master degrees might fi nd them useful for their formation. In the notes, starting from the basic principles of physics, the equations describing fl uid dynamics are derived. Some exact solutions of the problem of fl uid motion are determined and the approaches to be used to derive approximate solutions when the complexity of the problem prevents fi nding its solution in closed-form, are described. In particular, the fl ows at both low and high Reynolds numbers are considered. In the latter case, the inviscid fl uid and the irrotational fl ow models are described along with the the boundary layer which develops close to a rigid wall. The last part of the notes is devoted to turbulent fl ows, even though this topic is too broad to be discussed in depth in these brief note

Introduction to Morphodynamics of Sedimentary Patterns

Morphodynamics is a new discipline that investigates the formation and development of sedimentary patterns, i.e. the shapes of the cohesionless or cohesive boundaries of water bodies, evolving in response to the action of flowing water. Sedimentary patterns occur in fluvial, transitional, coastal and submarine environments. Their fascinating forms (e.g. dunes, meanders, alluvial fans, deltas, lagoons, coastal bars, tidal ridges, submarine fans) have attracted the attention of scientists. They also play a major role in fluvial, coastal and offshore engineering. The present monograph is the first of a series planned by an Editorial Committee comprising the four Authors. It provides a phenomenological introduction to the variety of patterns that will be investigated in the future Monographs. It also introduces to the mathematical theory of Morphodynamics, clarifying its nature of free boundary problem for the interface between a flowing water-sediment mixture and an erodible boundary

Role of the vertical pressure gradient in wave boundary layers

The pressure field in an oscillatory boundary layer is obtained by means of direct numerical simulations (DNS). The vertical pressure gradient is treated as any other turbulence quantity and its statistical properties are calculated from the DNS data. Moreover, a criterion involving the vertical pressure gradient is used to detect spots. The large fluctuations of the vertical pressure gradient, which take place in the turbulent flow, have significant implications for sediment transport

Prevalence and risk factors for atopic disease in a population of preschool children in Rome: Challenges to early intervention

Background: Allergic diseases are complex identities determined by an interplay of genetic and environmental factors, resulting in the clinical manifestation of the disease. So far in Italy, updated data about the prevalence and risk factors of respiratory and allergic diseases in preschool children are not available. Methods: Children aged 3-5 years, attending four different nursery schools in an urban district of the city of Rome. A standardized questionnaire developed under the SIDRIA-2 protocol was administered to the parents of the children for the assessment of the potential risk factors and the outcomes. Results: A total of 494 children were enrolled in the study; 289 of them (60.3%) performed a skin prick test (SPT). In the 12 months preceding the interviews, 15% of children experienced at least one episode of wheezing, 5.5% of allergic rhinitis, 11% of children had a doctor diagnosis of asthma, 12% of children who underwent the SPT were positive to at least one of the tested allergens, being diagnosed as atopic. The univariate analysis for the health outcomes of the study shows that asthma was positively associated with daycare attendance, mother's history of atopy, siblings' history of atopy, recurrent siblings' bronchitis, and dermatitis. Atopy was positively associated with mother's history of atopy and dermatitis, whereas there is a borderline protective association with recurrent siblings' bronchitis. Conclusions: This study represents a first comprehensive epidemiological evaluation of prevalence of respiratory and allergic diseases in children aged 3-5 years in the city of Rome and an updating of the evolution of allergic diseases

Updates on Children with Allergic Rhinitis and Asthma during the COVID‐19 Outbreak

Background: During the lockdown period caused by the SARS‐CoV‐2 pandemic, we monitored via online survey the trend of allergic symptoms and the therapeutic compliance in pa‐ tients followed at our center. Material and methods: In June 2020, we selected children followed at the Allergy and Immunology Service of Umberto I Hospital, aged between 6 and 16 years old, di‐ agnosed with asthma and/or rhinitis and sensitized to grass pollen or dust mite. We sent an email with 12 multiple‐choice questions investigating several areas: type of disease and sensitization, recurrence of symptoms, medication use during lockdown compared to the same period of the previous year. Results: The results of 82 questionnaires showed that 17.8% of patients suffered from asthma, 24.4% from rhinitis, and 57.8% from both. Within the group of asthmatic children, most of them presented an improvement of their symptoms. Likewise, with regard to allergic rhi‐ nitis, most of them reported better clinical conditions. Regarding treatment, we observed a global decrease in the use of on‐demand therapies (salbutamol, nasal corticosteroid, and antihistamine) for both pathologies. In addition, there was a reduction in the use of basal therapy for asthma and rhinitis from 2019 (23.3%) to 2020 (15.5%). Conclusions: Our data show a general trend of clinical improvement and a reduction in the use of on‐demand and basal therapy in allergic children during the lockdown

The Development of a European and Mediterranean Chickpea Association Panel (EMCAP)

Association panels represent a useful tool for quantitative trait loci (QTL) mapping and pre-breeding. In this study, we report on the development of a European and Mediterranean chickpea association panel as a useful tool for gene discovery and breeding. Chickpea (Cicer arietinum L.) is one of the most important food legumes worldwide and a key crop in the Mediterranean environments. The selection of genotypes followed criteria aimed to build a set of materials representative of the genetic diversity of chickpea germplasm focusing on the European and Mediterranean environments, which have largely been ignored to date. This tool can help breeders to develop novel varieties adapted to European and Mediterranean agro-ecosystems. Initially, 1931 chickpea accessions were phenotypically evaluated in a field trial in central Italy. From these, an association panel composed by 480 genotypes derived from single-seed descent was identified and phenotypically evaluated. Current and future phenotypic data combined with the genotypic characterization of the association panel will allow to dissect the genetic architecture of important adaptive and quality traits and accelerate breeding. This information can be used to predict phenotypes of unexploited chickpea genetic resources available in genebanks for breeding

The Role of Nasal Nitric Oxide and Anterior Active Rhinomanometry in the Diagnosis of Allergic Rhinitis and Asthma: A Message for Pediatric Clinical Practice

Background: Allergic rhinitis (AR) and asthma are two common atopic diseases, often associated with a common ethiopathogenesis characterized by a Th2 inflammatory response with the release of many biomarkers, such as nitric oxide (NO). Purpose: To evaluate and compare inflammatory (nFeNO and eFeNO) and functional (mNF and FEV1) parameters in AR children with or without asthma in comparison to controls. Secondly, we aimed to identify nFeNO cut-off values and verify their reliability to predict the presence of rhinitis or asthma alone or in combination. Patients and Methods: We enrolled 160 children (6– 12 years of age) with AR and/or asthma divided into four groups: controls, AR, asthma, and AR + asthma. All children underwent the following inflammatory and functional measurements: nFeNO, eFeNO, mNF and FEV1. Results: We observed that levels of nFeNO were extremely higher in children with AR and even more in those with AR + asthma in respect to controls. Notably, all the pathological conditions, especially AR + asthma, showed significantly lower values of mNF compared to healthy children. A negative correlation linked mNF and nFeNO. Then, we found eFeNO values significantly higher in all the pathological groups compared to controls, with major values of this marker in patients affected by asthma and AR + asthma, as well as FEV1 values significantly lower in all the disease groups, especially in children with asthma and AR+ asthma. ROC curve analysis showed that nFeNO was a great predictor for rhinitis alone or with asthma, revealing an accurate cut-off of 662 ppb. Conclusion: nFeNO measurement is non-invasive, easy to perform, economic and a valuable test in case of AR alone or in association with asthma. Thus, it should be used in patients with rhinitis, together with anterior active rhinomanometry (AAR) to diagnose and estimate the degree of nasal obstruction but also in children with asthma to assess their nasal involvement and improve the therapeutic management

16S metagenomics reveals dysbiosis of nasal core microbiota in children with chronic nasal inflammation: role of adenoid hypertrophy and allergic rhinitis

Allergic rhinitis (AR) and adenoid hypertrophy (AH) are, in children, the main cause of partial or complete upper airway obstruction and reduction in airflow. However, limited data exist about the impact of the increased resistance to airflow, on the nasal microbial composition of children with AR end AH. Allergic rhinitis (AR) as well as adenoid hypertrophy (AH), represent extremely common pathologies in this population. Their known inflammatory obstruction is amplified when both pathologies coexist. In our study, the microbiota of anterior nares of 75 pediatric subjects with AR, AH or both conditions, was explored by 16S rRNA-based metagenomic approach. Our data show for the first time, that in children, the inflammatory state is associated to similar changes in the microbiota composition of AR and AH subjects respect to the healthy condition. Together with such alterations, we observed a reduced variability in the between-subject biodiversity on the other hand, these same alterations resulted amplified by the nasal obstruction that could constitute a secondary risk factor for dysbiosis. Significant differences in the relative abundance of specific microbial groups were found between diseased phenotypes and the controls. Most of these taxa belonged to a stable and quantitatively dominating component of the nasal microbiota and showed marked potentials in discriminating the controls from diseased subjects. A pauperization of the nasal microbial network was observed in diseased status in respect to the number of involved taxa and connectivity. Finally, while stable co-occurrence relationships were observed within both control- and diseases-associated microbial groups, only negative correlations were present between them, suggesting that microbial subgroups potentially act as maintainer of the eubiosis state in the nasal ecosystem. In the nasal ecosysteminflammation-associated shifts seem to impact the more intimate component of the microbiota rather than representing the mere loss of microbial diversity. The discriminatory potential showed by differentially abundant taxa provide a starting point for future research with the potential to improve patient outcomes. Overall, our results underline the association of AH and AR with the impairment of the microbial interplay leading to unbalanced ecosystems