Un approccio numerico allo studio del moto ondoso all'interno di barriere frangiflutti virtuali e della stabilità della mantellata

2012 - 2013La presente tesi di dottorato intende presentare i risultati della validazione di una procedura numerica innovativa per la simulazione dell'interazione tra il moto ondoso e le barriere frangiflutti emerse. Prima di entrare nel merito di tale procedura si è ritenuto di introdurre il sistema costiero nel suo complesso e le problematiche ad esso correlate che rendono necessario, in talune circostanze, l'impiego di barriere frangiflutti di tipo sommerso o emerso al fine di preservare le fasce costiere stesse dall'attacco diretto del moto ondoso con conseguente erosione del litorale stesso. In questo spirito la presente tesi sarà articolata come segue: · In primo luogo sono presentate le definizioni fondamentali di litorale, di fascia costiera, di porto; vengono inoltre presentati i principali interventi messi in campo per la protezione della costa dall'erosione, nonché dei bacini portuali turistici e commerciali. Tra gli interventi di protezione di maggior impiego, vengono illustrate in modo approfondito alcune tipologie di opere, ovvero le barriere frangiflutti emerse, anche denominate "dighe marittime", poiché su queste ultime è incentrato il lavoro di ricerca svolto nei tre anni di dottorato. · Viene poi illustrato lo stato dell'arte nella modellazione numerica per ciò che attiene l'interazione tra il moto ondoso e le barriere frangiflutti emerse. In particolare è stato possibile osservare, attingendo alla letteratura scientifica di settore, che esistono due approcci numerici distinti rispetto a queste problematiche, il primo, più antico ed ormai quasi totalmente superato, in base al quale la barriera frangiflutti viene assimilata ad una struttura omogenea totalmente impermeabile. Il secondo, di più largo impiego e temporalmente più recente del primo, assimila la struttura ad un sistema multi-strato dotato di un nucleo totalmente impermeabile sul quale poggia uno strato poroso all'interno del quale l'onda frangente sulla struttura può infiltrarsi. Quest'ultimo approccio è denominato in letteratura "Modello di mezzo poroso" ed ha fornito risultati abbastanza attendibili, benché non del tutto soddisfacenti, nel valutare l'interazione tra il moto ondoso e le barriere emerse. In particolare questo approccio necessita della calibrazione dei parametri legati alla porosità del sistema che non sono di semplice ed immediata determinazione. Lo strato poroso che poggia sul nucleo impermeabile, infatti, dovrebbe simulare il comportamento della mantellata esterna della barriera ma, come si avrà modo di dimostrare all'interno del presente elaborato, tale approssimazione mal simula il comportamento reale del fluido all'interno della mantellata stessa, in quanto tutti i fenomeni turbolenti che all'interno di quest'ultima si generano, sono totalmente trascurati utilizzando tale approccio. Viene quindi presentato un modello numerico innovativo, oggetto della presente tesi di dottorato, che dovrebbe consentire di superare tali limitazioni dell'approccio numerico rispetto alle problematiche legate all'interazione tra il moto ondoso e le barriere frangiflutti emerse. · Lo scopo principale della presente tesi di dottorato è stato quello di effettuare una validazione del modello numerico implementato attraverso la comparazione dei risultati numerici con le evidenze presenti in letteratura scientifica. A tale scopo si è scelto di utilizzare dei parametri idraulici di grande rilievo nella progettazione e verifica di questa tipologia di opera, ovvero il run up, il coefficiente di riflessione e l'overtopping, le cui definizioni verranno fornite all'interno dell'elaborato. Per effettuare una validazione quanto più esaustiva possibile del modello sviluppato sono state ricostruite in 3D varie tipologie di opere a gettata, costituite da mantellate dotate di diversi massi naturali ed artificiali, la cui interazione con il moto ondoso è stata valutata prima con onde di tipo regolare e poi con onde di tipo random. · Infine vengono mostrati i risultati di una prima valutazione di massima della stabilità dei massi della mantellata esterna di barrire emerse attraverso la procedura numerica validata. · Seguono le conclusioni sul lavoro svolto. [a cura dell'autore]XII n.s

Numerical wave interaction with tetrapods breakwater

ABSTRACT: The paper provides some results of a new procedure to analyze the hydrodynamic aspects of the interactions between maritime emerged breakwaters and waves by integrating CAD and CFD. The structure is modeled in the numerical domain by overlapping individual three-dimensional elements (Tetrapods), very much like the real world or physical laboratory testing. Flow of the fluid within the interstices among concrete blocks is evaluated by integrating the RANS equations. The aim is to investigate the reliability of this approach as a design tool. Therefore, for the results' validation, the numerical run-up and reflection effects on virtual breakwater were compared with some empirical formulae and some similar laboratory tests. Here are presented the results of a first simple validation procedure. The validation shows that, at present, this innovative approach can be used in the breakwater design phase for comparison between several design solutions with a significant minor cost. KEY WORDS: Volume of Fluid (VOF), Wave, Run up, Reflection, Rubble mound, Numerical simulations, Tetrapod Flow 3D®, RANS equation

Bacterial inactivation/sterilization by argon plasma treatment on contaminated titanium implant surfaces: in vitro study

Background: Surface treatment by argon plasma is widely used as the last step of the manufacturing process of titanium implant fixtures before their sterilization by gamma rays. The possibility of using such a technology in the daily clinical practice is particularly fascinating. The aim of the present study was to assess the effects of the argon plasma treatment on different titanium implant surfaces previously exposed in vitro to bacterial contamination. Material and Methods: Sterile c.p. titanium implant discs with turned (T, Sa: 0.8μm), sandblasted/acid-etched (SAE, Sa: 1.3μm) and titanium plasma sprayed (TPS, Sa: 3.0μm) surface were used in this study. A strain of Aggregatibacter actinomycetemcomitans ATCC3718 was grown at 37°C under anaerobic conditions for 24 h and then transferred on six discs for each of the three surface types. After 24 hours, a half of the contaminated discs (control group) were directly used to evaluate the colony forming units (CFUs). The other half of the contaminated discs (test group) were treated in an argon plasma chamber for 12 minutes at room temperature prior to be analyzed for CFU counting. All assays were performed using triplicate samples of each material in 3 different experiments. Results: When the CFU counting was carried out on control discs, a total of 1.50x106±1.4x105, 1.55x106±7.07x104 and 3.15x106±2.12x105 CFU was respectively assessed for T, SAE and TPS discs, without statistically significant differences among the three surfaces. On the contrary, any trace of bacterial contamination was assessed for titanium discs treated in the argon plasma chamber prior to be analyzed, irrespectively to the implant surface tested. Conclusions: Within the limit of this study, reported data suggested that the argon plasma technology could be efficiently used to decontaminate/sterilize previously infected titanium implant surfaces

Quinine sulfate and bacterial invasion

BACKGROUND: As many patients who receive antimalarial drugs for treatment of noninfectious, inflammatory diseases are also immunosuppressed and might have a concomitant bacterial infection, we studied the effectiveness of these drugs against bacterial infections, to find out whether they could protect against (and even treat) such conditions and obviate the need for an additional antibiotic drug. METHODS: Effect of QS on bacterial growth: Escherichia coli (E. coli) HB101 pRI203 were cultured overnight at 37°C in TSB and inoculated (approx 1 × 10(7) cells /ml) in MEM in the presence of QS at various concentrations (0, 50 and 100 μM). The effect of QS at concentration of 50 and 100 μM on the entry process of E. coli HB101 pRI203 into HeLa cells was studied under different experimental conditions: 1. QS was incubated with 3 × 10(5) HeLa cells for 60 min at 37°C prior to infection. 2. QS was added to HeLa cell monolayers during the infection period. RESULTS: QS showed no antibacterial activity after 24 h of incubation. The invasive efficiency of the bacteria was significantly inhibited at a dose-dependent manner, when QS was added to HeLa cells for 60 min at 37°C prior to infection (condition 1), and to a lesser extent when added during the period of infection (condition 2). CONCLUSIONS: Although the antimalarials are generally regarded as being inactive against most extracellular bacterial species, our results indicate that QS significantly inhibited the internalization/invasion efficacy of E. coli in the host cells

Role of nutrition and adherence to the mediterranean diet in the multidisciplinary approach of hidradenitis suppurativa: Evaluation of nutritional status and its association with severity of disease

Hidradenitis suppurativa (HS) is a chronic, inflammatory and debilitating skin disorder. The exacerbating factors of HS include nutrition and adiposity. We aimed to investigate the relationships between body composition and the adherence to the Mediterranean diet (MD) with the severity of HS in a sample of naive-treatment patients with HS. In this case⁻controlled, cross-sectional study, we enrolled 41 HS patients and 41 control subjects. Body composition was evaluated by a bioelectrical impedance analysis (BIA) phase-sensitive system. PREvención con DIeta MEDiterránea (PREDIMED) and the 7-day food records were used to evaluate the degree of adherence to the MD and dietary pattern, respectively. The clinical severity was assessed by using the Sartorius HS score. HS patients had a worse body composition, in particular lower phase angle (PhA) (p < 0.001), and a lower adherence to the MD than controls, in spite of no differences in energy intake between the two groups. The receiver operator characteristic (ROC) analysis showing a value of PhA of ≤ 5.7 and a PREDIMED score of ≤ 5.0 identified HS patients with the highest clinical severity of the disease. After adjusting for sex, age, body mass index (BMI), and total energy intake, the HS Sartorius score maintained negative correlations with PhA (p < 0.001), PREDIMED score, and n-3 polyunsaturated fatty acids (p = 0.005). The results of the multivariate analysis showed PhA and PREDIMED score were the major determinants of HS Sartorius score, explaining 82.0% and 30.4% of its variability, respectively (p < 0.001). Novel associations were demonstrated between PhA and the degree of adherence to the MD with the HS severity. PhA and PREDIMED score might represent possible markers of severity of HS in a clinical setting

Antimicrobial Peptides Human Beta-Defensin-2 and -3 Protect the Gut During Candida albicans Infections Enhancing the Intestinal Barrier Integrity: In Vitro Study

The intestinal mucosa is composed of a monolayer of epithelial cells, which is highly polarized and firmly united to each other thanks to the presence of proteins complexes, called Tight junctions (TJs). Alteration of the mucus layer and TJs causes an increase in intestinal permeability, which can lead to a microbial translocation and systemic disorders. Candida albicans, in addition to its role of commensal, is an opportunistic pathogen responsible for disseminated candidiasis, especially in immunocompromised subjects where the dysbiosis leads to damage of the intestinal mucosal barrier . In this work, we used a line of intestinal epithelial cells able to stably express the genes that encodes human beta defensin-2 (HBD-2) and -3 (HBD-3) to monitor the invasion of C. albicans in vitro. Defensins are a group of antimicrobial peptides (AMPs) found in different living organisms, and are involved in the first line of defense in the innate immune response against pathogens. The results obtained show that the presence of antimicrobial peptides improves the expression of TJs and increases the Trans Epithelial Electrical Resistence value. In addition, the invasive ability of C. albicans in transfected cells is significantly reduced, as well as the expression levels of genes involved in the apoptotic pathway. Through the study of interaction between antimicrobial peptides and microbiota we will be able in the future to better understand the mechanisms by which they exert the host defense function against intestinal pathogens

Phase angle and Mediterranean diet in patients with acne: Two easy tools for assessing the clinical severity of disease

Acne is a chronic, inflammatory and debilitating skin disorder. Dietary factors and nutritional status are among the exacerbating factors of acne. Phase angle (PhA), a direct measure of Bioelectrical Impedance Analysis (BIA), represents an indicator of the chronic inflammatory state. The Mediterranean diet (MD) is a healthy dietary pattern that can exert anti-inflammatory effects in several inflammatory diseases. We aimed to investigate the difference in PhA and adherence to the MD and their associations with the severity of acne in a sample of naïve treatment patients with acne compared to control group

β2-adrenergic receptor and UCP3 variants modulate the relationship between age and type 2 diabetes mellitus

BACKGROUND: It is widely accepted that Type 2 Diabetes Mellitus (T2DM) and other complex diseases are the product of complex interplay between genetic susceptibility and environmental causes. To cope with such a complexity, all the statistical and conceptual strategies available should be used. The working hypothesis of this study was that two well-known T2DM risk factors could have diverse effect in individuals carrying different genotypes. In particular, our effort was to investigate if a well-defined group of genes, involved in peripheral energy expenditure, could modify the impact of two environmental factors like age and obesity on the risk to develop diabetes. To achieve this aim we exploited a multianalytical approach also using dimensionality reduction strategy and conservative significance correction strategies. METHODS: We collected clinical data and characterised five genetic variants and 2 environmental factors of 342 ambulatory T2DM patients and 305 unrelated non-diabetic controls. To take in account the role of one of the major co-morbidity conditions we stratified the whole sample according to the presence of obesity, over and above the 30 Kg/m(2 )BMI threshold. RESULTS: By monofactorial analyses the ADRB2-27 Glu27 homozygotes had a lower frequency of diabetes when compared with Gln27 carriers (Odds Ratio (OR) 0.56, 95% Confidence Interval (CI) 0.36 – 0.91). This difference was even more marked in the obese subsample. Multifactor Dimensionality Reduction method in the non-obese subsample showed an interaction among age, ADRB2-16 and UCP3 polymorphisms. In individuals that were UCP3 T-carriers and ADRB2-16 Arg-carriers the OR increased from 1 in the youngest to 10.84 (95% CI 4.54–25.85) in the oldest. On the contrary, in the ADRB2-16 GlyGly and UCP3 CC double homozygote subjects, the OR for the disease was 1.10 (95% CI 0.53–2.27) in the youngest and 1.61 (95% CI 0.55–4.71) in the oldest. CONCLUSION: Although our results should be confirmed by further studies, our data suggests that, when properly evaluated, it is possible to identify genetic factors that could influence the effect of common risk factors

Chitin Nanofibril-Nanolignin Complexes as Carriers of Functional Molecules for Skin Contact Applications

Chitin nanofibrils (CN) and nanolignin (NL) were used to embed active molecules, such as vitamin E, sodium ascorbyl phosphate, lutein, nicotinamide and glycyrrhetinic acid (derived from licorice), in the design of antimicrobial, anti-inflammatory and antioxidant nanostructured chitin nanofibrils–nanolignin (CN-NL) complexes for skin contact products, thus forming CN-NL/M complexes, where M indicates the embedded functional molecule. Nano-silver was also embedded in CN-NL complexes or on chitin nanofibrils to exploit its well-known antimicrobial activity. A powdery product suitable for application was finally obtained by spray-drying the complexes co-formulated with poly(ethylene glycol). The structure and morphology of the complexes was studied using infrared spectroscopy and field emission scanning electron microscopy, while their thermal stability was investigated via thermo-gravimetry. The latter provided criteria for evaluating the suitability of the obtained complexes for subsequent demanding industrial processing, such as, for instance, incorporation into bio-based thermoplastic polymers through conventional melt extrusion. In vitro tests were carried out at different concentrations to assess skin compatibility. The obtained results provided a physical–chemical, morphological and cytocompatibility knowledge platform for the correct selection and further development of such nanomaterials, allowing them to be applied in different products. In particular, chitin nanofibrils and the CN-NL complex containing glycyrrhetinic acid can combine excellent thermal stability and skin compatibility to provide a nanostructured system potentially suitable for industrial applications