1,721,321 research outputs found
Basics of NMR Spectroscopy (for Novices)
No full textThe NMR phenomenon is based on the detection of how an atomic nucleus with a non-null spin interacts with a magnetic field. Thus, NMR spectroscopy can be used to study any chemical element having a spinning nucleus. For organic chemists, this is a technique par excellence employed to retrieve the structure of “small” molecular compounds, by detecting 1H and 13C nuclei; however, with a few adaptations, it constitutes a very useful tool of general applicability for the detection of other elements and for the
characterization of complex systems such as supramolecular aggregates,
biomolecules and organic or inorganic materials. This, in turn, opens the
way to diverse applications in industrial, biomedical and environmental
contexts. NMR is a very versatile technique: indeed, it should be rather
considered as a constellation of different interrelated techniques, e.g. 1D
and 2D (correlation spectroscopy) spectroscopy in the liquid phase, NOEbased, TOCSY and solid-state techniques, relaxometry, and so on. Any
chemist is perfectly aware of the topics covered in this chapter; therefore, the following presentation aims at outlining the fundamental concepts and aspects of modern NMR for those people (engineers, biologists, environmentalists, physicians, etc.) who are not familiar with the subject. For a more detailed and exhaustive discussion, interested readers are strongly advised to consult the reference textbooks listed at the end of this presentation
The Use of NMR Techniques in Cultural Heritage
No full textAir pollution is deeply involved in the progressive degradation of Cultural Heritage. Therefore, environment technologies have to deal also with the analysis and preservation of monuments and artistic artefacts in general. Solid-state and mobile NMR techniques can be particularly helpful for monitoring the conservation state of Cultural Heritage, and for planning preservation actions in this sense. This chapter focuses on the basic principles of CP-MAS NMR and MOUSE NMR and on their applications in the context of artwork preservation. Some interesting cases of study are presented
Nuclear magnetic resonance with fast field-cycling setup: A valid tool for soil quality investigation
Full text linkNuclear magnetic resonance (NMR) techniques are largely employed in several fields. As an example, NMR spectroscopy is used to provide structural and conformational information on pure systems, while affording quantitative evaluation on the number of nuclei in a given chemical environment. When dealing with relaxation, NMR allows understanding of molecular dynamics, i.e., the time evolution of molecular motions. The analysis of relaxation times conducted on complex liquid-liquid and solid-liquid mixtures is directly related to the nature of the interactions among the components of the mixture. In the present review paper, the peculiarities of low resolution fast field-cycling (FFC) NMR relaxometry in soil science are reported. In particular, the general aspects of the typical FFC NMR relaxometry experiment are firstly provided. Afterwards, a discussion on the main mathematical models to be used to “read” and interpret experimental data on soils is given. Following this, an overview on the main results in soil science is supplied. Finally, new FFC NMR-based hypotheses on nutrient dynamics in soils are described
The Meaning of Pollution and the Powerfulness of NMR Techniques
No full textA short survey is presented herein on the use of the various Nuclear Magnetic Resonance (NMR) based techniques in the context of environmental analysis and environmental remediation. Starting from the general concept of “pollution” and its multifaceted aspects, a brief overview on the diverse use that NMR-related techniques may find in monitoring environmental problems and in providing useful tools for the implementation of smart solutions for environmental remediation is given. Future perspectives and challenges are briefly addressed
DFMKE: A dual fusion multi-modal knowledge graph embedding framework for entity alignment
No full textEntity alignment is critical for multiple knowledge graphs (KGs) integration. Although researchers have made significant efforts to explore the relational embeddings between different KGs, existing approaches may not describe multi-modal knowledge well in some tasks, e.g., entity alignment. In this paper, we propose DFMKE, a dual fusion multi-modal knowledge graph embedding framework, to address entity alignment. We first devise an early fusion method for fusing features of multi-modal entity representations of a KG. Simultaneously, multiple representations of various types of knowledge are generated independently by various techniques and fused by a low-rank multi-modal late fusion method. Finally, the outputs of early and late fusion methods are combined using a dual fusion scheme. DFMKE provides an ultimate fusion solution by leveraging the advantages of early and late fusion methods. Extensive experiments on two public datasets show that the DFMKE outperforms state-of-the-art methods by a significant margin achieving at least 10% more regard to Hits@n and MRR metrics
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
NMR Techniques for the Evaluation of Biochar Characteristics
No full textBiochar, a carbonaceous material, has emerged as a valuable tool for environmental remediation and soil fertility enhancement. Its activity - i.e., its ability to either change soil properties or affect the fate of organic and inorganic pollutants - depends on both biochar's physical and chemical characteristics. The most recent literature evidenced that conventional chemical analyses are insufficient to fully understand biochar’s functionality in environmental compartments. Therefore, new, and more sophisticated technologies are needed to unveil the mechanisms underlying biochar’s actions. In this chapter, the different NMR techniques for biochar evaluation are presented, and limits and advantages for each technique are acknowledged
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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