1,721,008 research outputs found
Dati preliminari sul Neogene Marino dell'Algeria Nord-Occidentale (bacino dello Chélif) e del Marocco Nord-Orientale (area di Melilla).
No full textNumerical dynamic characterisation of concrete bridge stays
No full textFollowing the recent collapse of a cable-stayed bridge in Genoa, Italy, an interest has arisen to understand if it would have been possible for unknown localised material deterioration and/or decrease in prestress levels to introduce noticeable changes in the dynamic behaviour of RC stays. As such, in this study we start by reviewing past research work, experimental and analytical, on the effects that prestress level may or may not have on the dynamic response of RC beam elements. We then review also available analytical formulations used to determine the natural frequency of vibration of prestressed beams, and, subsequently, complete the preliminary investigation on the effects of prestress levels, and local damage, through the analysis of finite element models of prestressed beams and stays. The comparison of analytical and numerical estimations with results obtained from an in-situ dynamic characterisation campaign on a RC bridge stay is also undertaken. In the second part of the study, we explicitly consider the Morandi bridge case-study, for which finite element models of the stays alone, as well as of the full bridge, are developed and analysed. The obtained results are then also compared with the observations made in pre-collapse in situ dynamic characterisation endeavours. All results obtained and discussed lead to the conclusion that, most regrettably, dynamic characterisation endeavours do not have the capability of providing insight on possible localised material deterioration or partial reduction of the average state of compression in this type of structural elements
Critical review and modelling of the construction sequence and loading history of the collapsed Morandi bridge
No full textThe Viaduct over the Polcevera River, designed by Riccardo Morandi, was a very strategic and important bridge, built in Genoa (Italy) in the mid-60s. In addition to being a renowned engineering work, due to a very innovative design at that period, the bridge was also considered as one of the symbols of the city. On the 14th of August 2018, however, a portion of this bridge suffered a catastrophic sudden collapse that caused 43 casualties. In order to be able to understand, within the context of the necessary numerical forensic investigations, the stress state to which the bridge was subjected to at the moment of collapse, it is first necessary to reproduce both its construction sequence, as well as the loading history the structure was subjected to throughout its life. This work is thus focussed on such task, as well as on showing the differences between the construction sequence that had been initially envisaged at the design stage and the one that was then actually followed during construction. The analyses carried out highlight how important is the correct modelling of the construction sequence, showing how the use of unknowingly incorrect inputs, may give rise to erroneous stress state estimations, which can then in turn mislead post-collapse forensic studies. In addition, the changes in permanent loading (e.g. addition of asphalt layers, replacement of road barriers) and time-dependent effects (e.g. concrete creep and prestress relaxation) over the course of the 51 years of life of the structure, are also scrutinised and discussed, with a view to try to reproduce as accurately as possible the stress state conditions of the structure at the time of its failure
How to: Diagnose inborn errors of intrinsic and innate immunity to viral, bacterial, mycobacterial, and fungal infections
No full textBackground: Inborn errors of intrinsic and innate immunity constitute the focus of a growing research field that investigates the molecular mechanisms underlying susceptibility to infections previously not considered part of the spectrum of inborn errors of immunity. These so-called nonconventional inborn errors of immunity often occur as infections caused by a narrow spectrum of microorganisms in otherwise healthy subjects. Objectives: This review aimed to provide a framework for identifying and evaluating patients with viral, bacterial, mycobacterial, and fungal infection needing further assessment for inborn errors of intrinsic and innate immunity. Sources: A literature search was performed using PubMed, from inception until 1 May 2022. The search included the following keywords: “inborn errors of immunity”; “inborn errors of innate immunity”; “primary immune deficiency”; “primary immunodeficiency”; “infections”; “infectious susceptibility”; “virus”; “pyogenic bacteria”; “mycobacteria”; “fungi”. All article types were considered. Content: We review the definition of what can be considered an inborn error of immunity and how the definition changed over the last ∼25 years. We further provide criteria to rule out secondary immunodeficiencies, identify patients needing further clinical and laboratory immunological assessment, and suspect and diagnose an inborn error of intrinsic and innate immunity. These steps are proposed as part of an algorithm. Implications: Patients with unexplained life-threatening infections, including otherwise healthy subjects, should be systematically screened for known inborn errors of immunity. The early diagnosis can prevent recurrence of life-threatening infections in the patients and reduce the total burden of infectious diseases
Inborn errors of immunity underlying a susceptibility to pyogenic infections: from innate immune system deficiency to complex phenotypes
No full textBackground: Pyogenic bacteria are associated with a wide range of clinical manifestations, ranging from common and relatively mild respiratory and cutaneous infections to life-threatening localized or systemic infections, such as sepsis and profound abscesses. Despite vaccination and the widespread use of effective antibiotic treatment, severe infection is still observed in a subset of affected patients. Objectives: We aim to summarize the available data regarding inborn errors of immunity that result in a high risk of severe pyogenic infections. Sources: Case series, as well as review and original articles on human genetic susceptibility to pyogenic infections were examined. Content: We review host-associated factors resulting in inborn errors of immunity and leading to a susceptibility to pyogenic infections, including deficiency in major components of the immune system (e.g., neutrophils, complement, immunoglobulin, and spleen function) and novel monogenic disorders resulting in specific susceptibility to pyogenic infection. Specifically, innate immune system deficiency involving toll-like receptors and associated signaling typically predispose to a narrow spectrum of bacterial diseases in otherwise healthy people, making a diagnosis more difficult to suspect and confirm. More complex syndromes, such as hyper IgE syndrome, are associated with a high risk of pyogenic infections due to an impairment of the interleukin-6 or -17 signaling, demonstrating the pivotal role of these pathways in controlling bacterial infections. Implications: In clinical practice, awareness of such conditions is essential, especially in the pediatric setting, to avoid a potentially fatal diagnostic delay, set the most proper and prompt treatment, and ensure prevention of severe complications
Failure analysis of the impact of a falling object on a bridge deck
No full textEven if not explicitly considered in most structural design codes, nor studied in-depth in past literature, reports from all over the world seem to indicate that accidental dropping of large heavy objects from transportation trucks can occur. The impact of such heavy objects onto the deck of a bridge can potentially give rise to the development of internal forces higher than those for which the bridge was designed to. To this end, the assessment of the response of bridges subjected to potential impacts from falling objects should be undertaken through idoneous numerical modelling. In recent years, the Applied Element Method (AEM) has been extensively employed to explicitly model complete structural response from the initial elastic stage all the way up to collapse and ensuing debris distribution. The present study, therefore, explores the capability of the AEM to model impact scenarios on bridge decks. It starts with a validation against experimental data available in the literature, and then passes onto the modelling of a case-study, the Morandi bridge, which at the time of its collapse, in August 2018, was being crossed by a truck carrying a heavy steel coil. However, initially use is also made of simplified analytical expressions available in the literature to estimate the forces generated by an impact of this type, with a view to gain additional confidence and reassurance on the obtained numerical results. A local model of the bridge span that the steel coil could have impacted is first developed to preliminarily assess different potential impact scenarios, followed by the analysis of a full model of the collapsed viaduct, including the estimation of debris distribution
NEONATAL INVASIVE HERPES INFECTIONS. INBORN ERRORS OF IMMUNITY AND PHENOCOPIES AS PREDISPOSING FACTORS
No full textHerpetic infection is a condition with high rates of neonatal morbidity and mortality; to date, there is no universally recognized strategy for the perinatal management of the risk of Herpes Simplex Virus (HSV) transmission based on the prognostic value attributed to maternal risk factors. Starting from the analysis of a clinical case of neonatal herpes meningoencephalitis, a literature review was conducted concerning the management of herpetic infection during pregnancy and in the neonatal period in terms of prevention and early diagnosis. The paper describes a case of a newborn with neonatal herpes meningoencephalitis transmitted by a mother with recurrent herpetic infection without clinically evident genital lesions at birth, despite the correct application of gynecological-neonatal protocols stratified by risk categories. An integrative model to the current guidelines should consider the following prophylactic strategies: performance of serological screening for HSV between the 24th and 28th week of pregnancy; provision of counseling regarding the main maternal-fetal and neonatal transmission risk factors for HSV; administration of antiviral prophylaxis with acyclovir to seropositive pregnant women starting from the 36th week of gestation; expansion of neonatal HSV-related screening tests even in cases where primary or recurrent genital lesions are present within ninety days before delivery. The diagnosis of neonatal herpetic meningoencephalitis suggests an underlying congenital error in innate immunity, related to an alteration in the TLR3/IFNα-β-λ axis, which presents with minimal/absent alterations in the immunological balance of I/II level, associated with infectious susceptibility to a restricted spectrum of viral pathogens, and deserves early immunological specialist evaluation
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