1,708 research outputs found
NMR conformational study of the lanthanide(III) complexes of DOTA in aqueous solution
No full textMarques, M.P.M. ; Geraldes, C.F.G.C. ; Sherry, A.D. ; Merbach, A.E. ; Powell, H. ; Pubanz, D. ; Aime, S. ; Botta, M
Numerical Analysis of Damage Iinitiation and Development in Bends of Steel Pipelines
No full textGasses and fluids are transported via an extensive infrastructure of steel pipelines. In the design of pipeline systems the use of elbows (pipe bends) is important because their flexibility makes them able to sustain significant deformations. These bends can be subjected to permanent deformations due to various load combinations which can lead to progressive material damage. There are three stages commonly observed in ductile damage: void nucleation, growth and coalescence. When subjected to varying bending loads low cycle fatigue damage may occur. Within this research project Finite Element Analysis is used to simulate the response of pipeline bends. Two element types are implemented to model a pipe bend, the classical shell element and an efficient tube element (pipe elbow element), respectively. To predict the structural response when subjected to monotonic loading a damage model is implemented for both elements. When subjected to cyclic loading three phases can be identified. During the first few cycles the permanent deformation increases rapidly. After some cycles, the rate of permanent deformation stabilizes until the point of response degradation. In order to capture this response a new material model, based upon the afore mentioned model, is proposed. Experiments have indicated that this model is well suited to determine the point of material failure.Structural MechanicsCivil Engineering and Geoscience
Metal Complexes as MRI Contrast Enhancement Agents
No full textMagnetic resonance imaging is one of the most efficient diagnostic modalities in clinical radiology and biomedical research. To enhance image contrast, paramagnetic complexes, mainly Gd3+ chelates, are used. Today, around one third of all medical MR images are generated with the use of a contrast medium and this number is expected to increase with the development of new applications and new agents. Recently, molecular imaging has emerged as a new area aiming at non-invasive visualisation of expression and function of bioactive molecules at the cellular level. Since any molecular imaging application requires a specific imaging probe, new chemical approaches become increasingly important. In this chapter, we discuss first proton relaxivity, the parameter that directly translates to the effectiveness of an MRI contrast agent. Many microscopic factors, including the hydration number, the water exchange rate, the rotational dynamics, as well as the electron spin relaxation, influence proton relaxivity for Gd3+ complexes. We show how the structure, the charge or the size of the chelate affects these factors. We also review the different strategies derived to obtain high-relaxivity probes. Non-toxicity of these agents is primordial for their application; therefore we also address the main physico-chemical aspects related to the in vivo stability of Gd3+-based agents, such as thermodynamic stability and kinetic inertness. The second part of the chapter is devoted to new-generation MRI contrast media, such as smart or responsive contrast agents that are capable of reporting on the physico-chemical environment in tissues. Among the huge number of systems reported in the field of smart MRI probes, we focus only on sensing of pH, redox state and metal ions. Many pathologies, such as stroke, infections, kidney disease and cancer are associated with significant pH variations. Accurate, high resolution, in vivo MRI pH mapping would be of great interest not only for diagnostic purposes but also for monitoring disease progression, choice and response to therapy. The partial oxygen pressure, pO2, is also significant in metabolic processes of cells, and its variation from normal values often indicates pathologies (ischemic diseases, strokes, tumors). As for metal ions, several of them play a crucial role in biological processes, whereas others are toxic. Alteration of the metal concentration in the body can often be correlated to disease states. Our objective here is to illustrate, via a few selected examples of Gd3+-based or Paramagnetic Chemical Exchange Saturation Transfer (PARACEST) agents, the major design principles in coordination chemistry to derive smart MRI probes using lanthanide complexes.LCI
CLASSICAL STUDIES:TO 155-TH ANNIVERSARY OF A.E. ALEKTOROV
No full textThe article, written in the genre of the response to read the book, devoted to the 155 anniversary since the birth of A. E. Alektorov. The author attempts to comprehend and describe the publishing and pedagogical activity of A.E. Alektorov for example, fundamental bibliographic work
The A.E. Coppard Papers at Syracuse
No full textSome of the most choice collections in the Manuscript Department of Syracuse University Libraries are also among the most modest in extent. The papers of English author and poet A.E. Coppard fit into both categories. Housed comfortably in a single box, fifty-five letters, three short stories in holograph and one speech provide a close look at Coppard\u27s literary theories, criticism, opinions of his own work and that of a few others, reaction to approaches regarding dramatizing, filming or televising his prose works, dealings with publishers, and his activities on behalf of world peace through the Authors\u27 World Peace Appeal in the early 1950\u27s
Covariance matrix-based fire and flame detection method in video
No full textThis paper proposes a video-based fire detection
system which uses color, spatial and temporal information.
The system divides the video into spatio-temporal blocks and
uses covariance-based features extracted from these blocks
to detect fire. Feature vectors take advantage of both the spatial and the temporal characteristics of flame-colored regions. The extracted features are trained and tested using a support vector machine (SVM) classifier. The system does not use a background subtraction method to segment moving regions and can be used, to some extent, with non-stationary cameras. The computationally efficient method can process 320×240 video frames at around 20 frames per second in an ordinary PC with a dual core 2.2 GHz processor. In addition, it is shown to outperform a previous method in terms of detection performance
The Ethical Economy of Customer Coproduction
No full textIn this article, the author argues that customer coproduction should be understood as an expression of a large-scale trend toward the increasing power and relevance of social production. Social production consists in the self-organized systems of (mostly immaterial) production that have evolved around the diffusion of networked information and communication tech-nologies. An analysis of the genealogy of social production is shared; this includes tracing it to the process of re-mediation of social relations put in motion by the expansion of the capitalist economy into the fields of culture and consciousness and the concomitant socialization of production relations. The author then argues that social production, including customer coproduction, follows a very particular economic logic—that is, an ethical economy where value is related to social impact rather than monetary accumulation. A detailed analysis of the logic of this ethical economy is offered; it draws out some implications for the successful management of ever more customer-centric brands, whereby the consumers are directly involved in the processes that add value
Raman and infrared study of hexamethylphosphoramide complexes of lanthanide perchlorates
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