Numerical modelling of composite laminates with through-thickness-reinforcements

The main objective of the present research study was to develop numerical models to investigate the mechanical properties and effectiveness of z-fibre reinforced laminates. A survey of relevant literature on through-thickness reinforcements (TTR) was undertaken and z-fibre pinning was chosen as the main topic of study. The development of numerical tools was mainly based on the finite element (FE) method and was carried out at different model scale levels. At a micro-mechanical level of analysis, two models were presented. Firstly a unit cell FE model based on the actual geometric configuration of a z-pinned composite was used. Calculations were performed to understand how the through-thickness reinforcement modified the engineering elastic constants and local stress distributions. Secondly the study of an analytical micro-mechanical model was undertaken. The model simulated a z-fibre bridging a delamination crack tinder mixed-mode loads. A constitutive law relating the z-pin bridging forces with the crack displacements was defined as the "bridging law". Numerical examples for z-fibre bridging laws under Mode I and Mode II loads were computed along with design evaluations of the effect of several micro-mechanical parameters on the bridging laws. This analytical model was then implemented into a MATLAB code specifically written by the author. The code generated constitutive relationship for interface elements simulating the bridging laws of a single z-pin to be used in a FE analysis. A detailed numerical study of the mode I interlaminar fracture of composite laminates with z-pins was then carried out. AFL• model of a double cantilever beam (DCB) was developed. The numerical analysis focused on the large scale bridging (LSB) caused by z-pins mechanics, which increased the laminate resistance against delamination growth. The numerical results were validated against experimental data. Computational curves for the energy balance and energy rates were also determined showing that the LSB process consumed a significant amount of irreversible energy. The assumption made by the linear elastic fracture mechanics (LEFM) that all energy dissipations were included in the fracture energy and confined within the damage front, was not valid for z-pinned laminates. The FE analysis was then extended to study a curved single-lap shear joint, to prove the effectiveness of TTR against debond failure of the joint. The presence of TTR was shown to delay the propagation of the debonding and generally to enhance the load carrying capability of the joint. TTR is proved to be more effective in reducing the Mode I component of debonding driving force than that of the Mode II. Finally a global-local approach was proposed to implement the TTR elements into large composite stnictural FE models. Possible future studies for TTR numerical modelling were also addressed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

G-genotyping of rotaviruses in stool samples in Salento, Italy

Rotaviruses are the most common agents of diarrhoeal illnessin infants and young children. Gastroenteritis caused byrotaviruses is also more likely to be associated with severe dehydration compared to other viral gastroenteritis.We determined the G-genotype of rotaviruses circulating in theSalento. During 2004, 144 stool samples were collected fromsubjects with a positive screening test and stored at -20 °C untilconfirmation could take place using molecular biology techniques. A reverse transcription-polymerase chain reaction (RTPCR) assay for the amplification of gene VP7 of rotavirus wasdeveloped and used; G-genotype was determined by sequencing and phylogenetic analysis. A total of 101 stool samples were detected positive by RT-PCRand 35 were sequence analyzed and classified into G1, G2, G4,G9 and G12 type. The overall relative incidence of G-types inSalento is different to that of other developed countries. Themost prevalent genotype was G2 while genotype G1 was present at low levels. It is also interesting to note the presence ofG9 rotavirus, which is now recognized as the fifth globallyimportant rotavirus genotype.In this study, therefore, we demonstrate the usefulness of a simple method for correctly determining the G genotypes circulating in a geographic region

Unusual cause of right iliac fossa pain: sigmoid perforation due to ingested rabbit bone. Case report

Disorders of an organ not usually found in the right iliac fossa, such as the sigmoid colon, are an uncommon cause of right iliac fossa pain. We present a case of right iliac fossa pain caused by a sigmoid perforation due to involuntary ingestion of a rabbit bone, and describe the main features of this condition

Can Sleep microstructure improve diagnosis of OSAS? Integrative information from CAP parameters

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Teacher Stress and burnout: a study using MIMIC modelling

A number of recent studies carried out in the education sector have revealed the incidence of burnout in school environments and have highlighted the principal psycho-social sources of burnout syndrome among teachers. This study attempts to look further at the results of a previous research carried out on a sample of 882 Italian teachers. Using advanced statistical techniques such as MIMIC modelling, it intends to verify whether the following psycho-social stress factors are significant as predictors: interpersonal relations, workload, organisational conflict, role ambiguity, perceived role image, work-home interface. Considering that in Italy the recent regulations regarding retirement are triggering new stressful conditions for teachers, this study also aims to assess the role played by age in relation to the sources of psycho-social stress and burnout. The scales we have adopted are the Maslach Burnout Inventory (MBI-ES) and the Cooper’s Occupational Stress Indicator (OSI) specifically adapted for Italian schools. Results have shown the clear predictive role of factors such as interpersonal conflict and home-work interface in determining the onset of emotional exhaustion and depersonalization among teachers

Smoking E-CigaRette and HEat-noT-burn Products: the SECRHET study, a large observational survey among young people in Italy

Aim: Electronic cigarettes (eCig) and heated tobacco products (HTP), that heat a solution (e-liquid) to create vapour and tobacco at a temperature below the point of combustion, respectively, are emerging forms of smoking device widely diffused. The aim of this study was to investigate knowledge, attitudes and behaviour toward HTP among young people in Italy. Methods: The Smoking E-CigaRette and HEat-noT-burn products (SECRHET) study was an online survey carried out in April 2019 using the platform Skuola.net, a platform where 2.5 million students are registered. Questions were related to knowledge about new generation smoking products, such as “Do you know what happens to tobacco when you use a heat-not-burn product?”, “Do you think electronic cigarettes create addiction?”, “Are products that use heated tobacco harmful to health?”, “Are electronic cigarettes harmful to health?”, “Have you ever heard of products that use heated tobacco?”, “Is nicotine present in products that use heated tobacco?”  Results: A total of 13882 people completed the questionnaire, of which 8056 (58%) were females. Regarding smoking habits, 3393 (24.4%) declared to be current cigarette smokers, while 802 (5.8%) and 3173 (22.9%) were current and former e-cigarette smokers, respectively. Moreover, 715 (5.2%) and 1148 (8.3%) declared to be current and former heat-not-burn cigarette smokers. The variables associated to both eCig and HTP use were current smoking, age over 18 years, male gender, and residence in Central and Southern Regions. Concerning knowledge issues, almost half of respondents believe that electronic cigarettes are addictive and are harmful to health. Moreover, most of respondents do not know what happens to tobacco when using a heated tobacco device and if heated tobacco products are harmful to health. Conclusion: The prevalence of eCig and HTP use is higher among young people in Italy compared to adults and older people, and requires adequate public health interventions.     Conflicts of interest: None declared.   Funding: This research received no external funding.   Acknowledgments: The authors are grateful to the personnel of skuola.net

Smoking E-CigaRette and HEat-noT-burn Products: the SECRHET study, a large observational survey among young people in Italy

Aim: Electronic cigarettes (eCig) and heated tobacco products (HTP), that heat a solution (e-liquid) to create vapour and tobacco at a temperature below the point of combustion, respectively, are emerging forms of smoking device widely diffused. The aim of this study was to investigate knowledge, attitudes and behaviour toward HTP among young people in Italy. Methods: The Smoking E-CigaRette and HEat-noT-burn products (SECRHET) study was an online survey carried out in April 2019 using the platform Skuola.net, a platform where 2.5 million students are registered. Questions were related to knowledge about new generation smoking products, such as “Do you know what happens to tobacco when you use a heat-not-burn product?”, “Do you think electronic cigarettes create addiction?”, “Are products that use heated tobacco harmful to health?”, “Are electronic cigarettes harmful to health?”, “Have you ever heard of products that use heated tobacco?”, “Is nicotine present in products that use heated tobacco?”  Results: A total of 13882 people completed the questionnaire, of which 8056 (58%) were females. Regarding smoking habits, 3393 (24.4%) declared to be current cigarette smokers, while 802 (5.8%) and 3173 (22.9%) were current and former e-cigarette smokers, respectively. Moreover, 715 (5.2%) and 1148 (8.3%) declared to be current and former heat-not-burn cigarette smokers. The variables associated to both eCig and HTP use were current smoking, age over 18 years, male gender, and residence in Central and Southern Regions. Concerning knowledge issues, almost half of respondents believe that electronic cigarettes are addictive and are harmful to health. Moreover, most of respondents do not know what happens to tobacco when using a heated tobacco device and if heated tobacco products are harmful to health. Conclusion: The prevalence of eCig and HTP use is higher among young people in Italy compared to adults and older people, and requires adequate public health interventions. &nbsp

Genetic deletion of α7 nicotinic acetylcholine receptors induces an age-dependent Alzheimer's disease-like pathology.

The accumulation of amyloid-beta peptide (Aβ) and the failure of cholinergic transmission are key players in Alzheimer's disease (AD). However, in the healthy brain, Aβ contributes to synaptic plasticity and memory acting through α7 subtype nicotinic acetylcholine receptors (α7nAChRs). Here, we hypothesized that the α7nAChR deletion blocks Aβ physiological function and promotes a compensatory increase in Aβ levels that, in turn, triggers an AD-like pathology. To validate this hypothesis, we studied the age-dependent phenotype of α7 knock out mice. We found that α7nAChR deletion caused an impairment of hippocampal synaptic plasticity and memory at 12 months of age, paralleled by an increase of Amyloid Precursor Protein expression and Aβ levels. This was accompanied by other classical AD features such as a hyperphosphorylation of tau at residues Ser 199, Ser 396, Thr 205, a decrease of GSK-3β at Ser 9, the presence of paired helical filaments and neurofibrillary tangles, neuronal loss and an increase of GFAP-positive astrocytes. Our findings suggest that α7nAChR malfunction might precede Aβ and tau pathology, offering a different perspective to interpret the failure of anti-Aβ therapies against AD and to find novel therapeutical approaches aimed at restoring α7nAChRs-mediated Aβ function at the synapse