86,696 research outputs found
The key role of nitric oxide in hypoxia: hypoxic vasodilation and energy supply-demand matching
No full textSignificance: a mismatch between energy supply and demand induces tissue hypoxia with the potential to cause cell death and organ failure. Whenever arterial oxygen concentration is reduced, increases in blood flow - 'hypoxic vasodilation' - occur in an attempt to restore oxygen supply. Nitric oxide is a major signalling and effector molecule mediating the body's response to hypoxia, given its unique characteristics of vasodilation (improving blood flow and oxygen supply) and modulation of energetic metabolism (reducing oxygen consumption and promoting utilization of alternative pathways). Recent advances: this review covers the role of oxygen in metabolism and responses to hypoxia, the hemodynamic and metabolic effects of nitric oxide, and mechanisms underlying the involvement of nitric oxide in hypoxic vasodilation. Recent insights into nitric oxide metabolism will be discussed, including the role for dietary intake of nitrate, endogenous nitrite reductases, and release of nitric oxide from storage pools. The processes through which nitric oxide levels are elevated during hypoxia are presented, namely (i) increased synthesis from nitric oxide synthases, increased reduction of nitrite to nitric oxide by heme- or pterin-based enzymes and increased release from nitric oxide stores, and (ii) reduced deactivation by mitochondrial cytochrome c oxidase. Critical issues: several reviews covered modulation of energetic metabolism by nitric oxide, while here we highlight the crucial role NO plays in achieving cardiocirculatory homeostasis during acute hypoxia through both vasodilation and metabolic suppression Future directions: we identify a key position for nitric oxide in the body's adaptation to an acute energy supply-demand mismatc
Big Tech corporations and AI: A Social License to Operate and Multi-Stakeholder Partnerships in the Digital Age
No full textThe pervasiveness of AI-empowered technologies across multiple sectors has led to drastic changes concerning traditional social practices and how we relate to one another. Moreover, market-driven Big Tech corporations are now entering public domains, and concerns have been raised that they may even influence public agenda and research. Therefore, this chapter focuses on assessing and evaluating what kind of business model is desirable to incentivise the AI for Social Good (AI4SG) factors. In particular, the chapter explores the implications of this discourse for SDG #17 (global partnership) and how this goal may encourage Big Tech corporations to strengthen multi-stakeholder partnerships that promote effective public-private and civil society partnerships and the meaningful co-presence of non-market and market values. In doing so, the chapter proposes an analysis of the sociological notion of "social license to operate" (SLO) elaborated in the mining and extractive industry literature and introduces it into the discourse on sustainable digital business models and responsible management of risks in the digital age. This serves to explore how such a social license can be adopted as a practice by digital business models to foster trust, collaboration and coordination among different actors - AI researchers and initiatives, institutions and civil society at large - for the support of SDGs interrelated targets and goals
From Subjectivity to Objectivity: Bernard Lonergan's Philosophy as a Grounding for Value Sensitive Design
No full textThis article explores the potential of Bernard Lonergan’s philosophy of subjectivity as objectivity as a grounding for value sensitive design (VSD) and the design turn in applied ethics. The rapid pace of scientific and technological advancement has created a gap between technical abilities and our moral assessments of those abilities, calling for a reflection on the philosophical tools we have for applying ethics. In particular, applied ethics often presents interconnected problems that require a more general framework for ethical reflection. Lonergan’s philosophy, which emphasizes the importance of selfunderstanding and self‐transcendence in achieving objectivity, can provide a valuable perspective on VSD and the design turn in applied ethics. The article examines how Lonergan’s philosophy can be applied to VSD and the design turn, and how scientific knowledge can be integrated into an ethics of science without reducing it to an external reflection. By adopting Lonergan’s perspective, we can address the ethical challenges arising from scientific and technological advancements while promoting a more holistic approach to applied ethics
ALE simulation of orthogonal cutting: a new approach to model heat transfer phenomena at the tool-chip interface
No full textThis paper presents a new procedure to evaluate the global heat transfer coefficient in orthogonal cutting. The knowledge of the actual heat transfer conditions is a fundamental issue as far as the life, tool wear and tool substitution interval are regarded. More in detail, an Arbitrary Lagrangian-Eulerian approach was utilised to model orthogonal cutting process and the numerical simulations were validated by making experimental tests for identifying cutting forces and internal tool temperatures. A mild steel was cut utilising both an uncoated (WC) and a coated (TiN) tool. On the basis of both experimental and simulative data, a consistent model of the global heat transfer coefficient as function of the local pressure and temperature at the tool-workpiece interface was developed
A simple model for predicting the thermal flow on the tool in orthogonal cutting process
No full textWear Modeling in Mild Steel Orthogonal Cutting when using Uncoated Carbide Tools
No full textWear prediction in machining has been recently studied by FEM although the use of numerical methods for such applications is still a very challenging research issue. In fact, wear phenomenon involves many aspects related to process mechanics which require a very accurate modelling. In other words, only a very punctual code set-up can help the researchers in order to obtain consistent results in FE analysis. The high relative velocity between chip and tool requires effective material models as well as friction modelling at the interface. Moreover the prediction of temperature distribution is another critical task; in the paper some different procedures are discussed. Subsequently a wear model is presented and calibrated in order to obtain a suitable tool to be implemented in a FE code with the aim to describe the wear evolution during the simulation process. A proper designed experimental campaign supplied some reference data for model set-up and verify in the practical application. All these aspects are carefully discussed in the pape
Finite Element Modeling of Microstructural Changes in Turning of AA7075-T651 Alloy and Validation
No full textThe surface characteristics of a machined product strongly influence its functional performance. During machining, the grain size of the surface is frequently modified, thus the properties of the machined surface are different to that of the original bulk material. These changes must be taken into account when modeling the surface integrity effects resulting from machining. In the present work, grain size changes induced during turning of AA 7075-T651 (160 HV) alloy are modeled using the Finite Element (FE) method and a user subroutine is implemented in the FE code to describe the microstructural change and to simulate the dynamic recrystallization, with the consequent formation of new grains. In particular, a procedure utilizing the Zener-Hollomon and Hall-Petch equations is implemented in the user subroutine to predict the evolution of the material grain size and the surface hardness when varying the cutting speeds (180 - 720 m/min) and tool nose radii (0.4 - 1.2 mm). All simulations were performed for dry cutting conditions using uncoated carbide tools. The effectiveness of the proposed FE model was demonstrated through its capability to predict grain size evolution and hardness modification from the bulk material to machined surface. The model is validated by comparing the predicted results with those experimentally observed
Impiego di Tecniche Sperimentali per l'Analisi della Formazione di White Layer in seguito al Processo per Asportazione di Truciolo su acciai Induriti
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