1,721,286 research outputs found
Tritium hazard and measurement
No full textTritium hazard is related to its radioactive nature. It has characteristics that present a special challenge for health-risk assessment and measurement procedures. Tritium hazard will be investigated considering tritiated water in liquid phase, gaseous form, tritium oxide (HTO) and special tritium compounds. The different ways of tritium irradiation will be considered. External irradiation will be discussed and the higher effort will be devoted to the analysis of the tritium intake in the human body through inhalation, ingestion and diffusion through body skin. The main health physics aspects connected with tritium will be exposed considering the following: parameters for risk estimation, risks due to multiple exposition from different physical and chemical form of tritium, compounds and from additional radiation sources, specific dose contributions due to the intake of tritium in its different forms, intake prevention and recovery, low level tritium exposure, regulatory limits for tritium release and disposal. Methods for sampling and measuring tritium will then be exposed. Among the others the following techniques will be considered: Removable contamination collection with a smear-test filter, Tritium in air measurement with ion-chamber and gas flow proportional counters, Tritium in water analysis with low-level liquid scintillation counters, Passive tritium oxide sampling for indoor atmosphere monitoring. Consideration about measurement effectiveness for obtaining the needed levels of accuracy will be issued taking into account the determination of the main parameters need to characterize a tritium contaminated area. Radio-toxicological analysis for assessing the tritium intake will be also described and discussed. ©2013 Nova Science Publishers, Inc. All rights reserved
Characterization and Design of Multilayer PBO FRCM Composite Reinforcements for Concrete Structures
No full textFiber-reinforced cementitious matrix (FRCM) composites can be preferred to other techniques to strengthen reinforced concrete (RC) members. Due to the limited cross-sectional area of textiles in FRCM, multilayer composites are often needed to provide adequate strength increase. Although multilayer FRCM composites have been already employed, quite limited research is available regarding the bond behavior of multilayer FRCM-concrete joints. Direct shear tests of FRCM-concrete joints and bending tests of FRCM-strengthened RC beams showed that when one or two textile layers are employed, debonding at the matrix-fiber interface generally occurs. When more than two layers are employed, detachment of the FRCM strip was observed in FRCM-strengthened RC beams, while limited studies of corresponding FRCM bond behavior were performed. The bond behavior of a multilayer bidirectional polyparaphenylene benzobisoxazole (PBO) FRCM composite applied onto a concrete substrate is investigated in this paper. Single-lap direct shear tests of PBO FRCM-concrete joints comprising two or four textile layers are performed, along with tensile tests of bare textile strips and single-layer FRCM coupons. Tests were conducted in both textile directions. The results obtained provide fundamental information on the effect of the textile direction and number of layers to be considered when designing the reinforcing system
Terlipressin as rescue treatment of refractory shock in a neonate
No full textPatients with septic shock may develop refractory hypotension despite maximal inotropic support with impairment of clinical outcome. Terlipressin, a long-acting vasopressin analogue, is reported to be effective as rescue treatment of refractory septic shock in adult and paediatric patients, while clinical experience in neonates is definitely scarce. We report a neonate with systemic inflammatory response syndrome after surgery for abdominal neuroblastoma who received terlipressin as rescue treatment after failure of volume load and catecholamines. Terlipressin promptly reversed hypotension and improved tissue perfusion without adverse effects. Conclusion: Terlipressin appears an effective rescue treatment in patients with refractory vasodilatory septic shock. Further studies are required to assess its efficacy and safety in neonatal population. © 2008 The Author(s)
Web Engineering at the frontiers of the Web 2.0: Design Patterns for online 3D Multiuser Spaces
No full textOnline 3D Shared Spaces (3DSSs) can be regarded as a frontier of the Web 2.0, where users as participants contribute to create a meaningful, engaging experience. Like other complex web applications, the development and evolution of high-quality 3DSS applications requires methodological support—through models, methods, and principles.
Yet, the application of structured, engineered approaches to this domain is largely unexplored. The purpose of this paper is to contribute to bridging Web Engineering to the 3DSS world by means of design patterns. We present five patterns that focus on two
factors deemed necessary for effective experiences in a 3DSS: Presence (i.e. the feeling of “being there”, typical of “virtual worlds”) and Long-Term Engagement (typical of successful Web 2.0 communities). The patterns presented in the paper distil our large scale
experiences with 3DSSs (that have involved so far over 9,000 youngsters from 3 continents) and are discussed in the light of existing literature
Experimental procedures for the mechanical characterization of composite reinforced mortar (CRM) systems for retrofitting of masonry structures
Full text linkFiber-reinforced composites can be arranged in the form of bi-dimensional grids and employed as internal reinforcement of mortar plasters to realize composite reinforced mortar (CRM) systems. Recently, CRM were applied as externally bonded reinforcement of existing masonry members showing promising improvements of load-carrying and deformation capacities. However, since CRM systems are still in their infancy, limited research is available regarding their mechanical properties and their bond behavior with respect to masonry substrates. In this paper, a series of experimental tests are performed on a CRM system comprising a glass fiber-reinforced composite grid and a lime-based matrix. Namely, tensile tests of bare grid yarns and of CRM coupons, shear tests of grid joints, and single-lap direct shear tests of CRM-masonry joints were performed. These tests are aimed at providing a comprehensive mechanical characterization of the CRM, which results can be used to design strengthening applications with this system. Namely, the tensile properties of bare grid yarns in warp and weft direction are obtained and compared with those of CRM coupons tested following the indications of the Italian and U.S. acceptance criteria for inorganic-matrix composites. Furthermore, the grid joints are subjected to shear tests to determine if the yarns orthogonal to the applied load direction provide a contribution to the system load-carrying capacity. Finally, CRM-masonry joints are subjected to single-lap direct shear tests to study the CRM bond behavior. This work provides an insight on the behavior of CRM that can be useful to formulate reliable design procedures for these systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dopamine administration in very low birth weight preterm infants: Emerging issues on endocrine effects
No full textPreterm newborns weighing less than 1500 g (very low birth weight infants, VLBW) represent a critical population with high prevalence of morbidities, often requiring hemodynamic stabilization. Dopamine is a natural cathecolamine widely used for this purpose because it exerts pleiotropic anti-shock effects on cardiovascular, renal and endocrine systems, acting on adrenergic and dopaminergic receptors. Dopamine is a first choice drug in VLBW infants for inotropic support and optimisation of renal and splanchnic perfusion, mostly indicated for the treatment of hypotension, symptomatic patent ductus arteriosus and renal failure. Dopamine reversibly suppresses pituitary functions in adults but its effects on endocrine balance have been poorly studied in VLBW infants. Recent studies showed a dose-dependant reduction of TSH and T4 plasmatic levels in dopamine-treated VLBW infants and a positive correlation between dopamine infusion and incidence of transient hypothyroxinemia of prematurity. Further studies demonstrated that dopamine infusion also reduces PRL secretion in VLBW infants. TSH, T4 and PRL suppression rapidly reverses after dopamine withdrawal, when a significant hormonal rebound is observed. Therefore, such iatrogenic suppression probably cannot involve long-term injuries and T4 substitutive administration appears unecessary during short course dopamine treatment. Recent observations suggest that dopamine infusion can prevent early diagnosis of congenital hypothyroidism (CH) when screening programs are merely based on TSH plasmatic levels. Considering the severe neurodevelopmental outcome of undiagnosed CH, other screening strategies should be considered in treated neonates, such as simultaneous T4 and TSH testing and hormonal re-evaluation after dopamine discontinuation. © 2007 Bentham Science Publishers Ltd
Diagonal shear behavior of historic walls strengthened with composite reinforced mortar (CRM)
No full textComposite reinforced mortar (CRM) represents an innovative strengthening solution for existing masonry structures. CRM is comprised of a composite grid embedded within an inorganic matrix (mortar) and it is applied as externally bonded reinforcement of masonry members. The composite grid bears the tensile stresses whereas the inorganic matrix is responsible for the stress-transfer between the composite grid and the substrate. CRM showed promising results in improving the mechanical properties of different masonry members, such as walls and arches. However, a full understanding of the mechanical behavior of CRM strengthened masonry members is still missing, which hinders the formulation of reliable CRM design guidelines. In this paper, an experimental investigation of the in-plane behavior of masonry walls made by historical bricks and strengthened with a CRM comprised of a glass fiber composite grid embedded in a lime-based mortar is presented and discussed. The parameters studied are the wall dimension and type (double leaf with and without diatoni). Furthermore, the effect of steel anchors on the strengthened wall capacity is investigated. The results obtained are finally analyzed using simple analytical formulations
Fatigue tensile testing of glass fiber-reinforced polymer reinforcing bars
No full textGlass fiber-reinforced polymer (GFRP) bars are a valid alternative to traditional steel bars for reinforcing concrete structures in specific situations. Although the elastic modulus of GFRP bars is generally 20–25% of that of steel bars, which entails for a higher cross-sectional area of GFRP than of steel bars for the same axial stiffness, they have superior durability with respect to the steel counterpart, which makes them suitable for applications in aggressive environments, such as those exposed to the chloride attack. Among these, RC bridge decks represent a typical case where GFRP bars strongly increases the structure durability, since they do not suffer for the chloride attack caused by the use of deicing agents. Bridge decks are subjected to cyclic loads that may induce fatigue issues. However, quite limited studies are available in the literature regarding the fatigue behavior of GFRP bars. In this paper, the test method for tensile fatigue provided by the European standard ISO 10406–1 is discussed and modified to account for the actual cyclic stresses applied to representative RC members subjected to fatigue, namely bridge decks. The results of a tensile test of a GFRP bar according to the modified procedure are then presented and discussed
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