1,720,976 research outputs found
Towards enantioselective total synthesis of metabolites from Laurencia species: an NMR-based approach to structural discrimination
Get PDFI. Il singolare caso dell'Itomanallene B: Suzuki vs Vairappan
Il presente lavoro si propone di validare l'ipotesi dei chemical shift attraverso la sintesi degli epimeri cis e trans dell'Itomanallene B, utilizzando la metodologia sviluppata per la reazione di Alchilazione Allilica Asimmetrica di Tsuji-Trost. A quanto ci risulta, si tratta del primo tentativo di sintetizzare queste molecole, presentanti sia un bromoallene stereodefinito sia un diene skippato.
II. Studio del meccanismo di diossigenazione elettrossidativa degli alleni
Un aspetto centrale di questa ricerca è lo sviluppo e l'ottimizzazione di una nuova blanda ossidazione, per gli alleni.
Particolare attenzione sarà dedicata alla comprensione del meccanismo di reazione, studiato attraverso l'uso di voltammetria ciclica (CV), studi computazionali e analisi tramite ReactNMR.
Inoltre, viene proposto un nuovo intermedio: vinil-TEMPO, che potrebbe rappresentare un intermedio cruciale per la trifunzionalizzazione degli alleni. Esempi preliminari vengono forniti a supporto, suggerendo la potenziale applicazione di questa strategia in contesti sintetici futuri.I. The strange case of Itomanallene B: Suzuky vs Vairappan
The aim of this work is to validate our hypothesis about the chemical shift by synthesizing both the CIS and TRANS epimers of Itomanallene B, using the previously developed methodology for the Tsuji-Trost Asymmetric Allylic Alkylation reaction. To the best of our knowledge, this will be the first attempt to synthesize these molecules which incorporate both a stereodefined bromoallene and a skipped diene.
II. Elucidating the mechanism of electrooxidative allene dioxygenation
A key aspect of this research will involve studying and optimizing a novel mild oxidation method specifically tailored for allenes. Special emphasis will be placed on elucidating the reaction mechanism, which will be investigated through cyclic voltammetry (CV), computational studies, and the ReactNMR method.
Moreover, we propose the involvement of a novel intermediate, a vinyl-TEMPO, which may serve as a key step towards achieving allene trifunctionalization. Preliminary examples supporting this pathway have been provided, further suggesting its potential applicability in future synthetic strategies
Do Drones dream of a Resilient and Sustainable Urban Distribution? A Literature Review
Get PDFOver the last 20 years, the demand for transport services has grown thanks to increasing globalization and e-commerce exponentially. This led to the rise in externalities (e.g., air pollution, climate change, noise pollution, traffic congestion), an issue that is particularly relevant in urban contexts. The improvement of last-mile delivery processes comes as a natural necessity. The considerable pressure on urban systems was further pushed by the outbreak of COVID-19, which highlighted the need for a delivery system able to provide a fast, resilient and safe contactless solution to reach isolated or quarantined areas with ease. To cope with the abovementioned issues, many authors have been looking toward adopting unmanned aerial vehicles (a.k.a. drones) in logistics. Therefore, this work aims to identify how drones can improve last-mile logistics resilience and sustainability and understand the impact of drones on urban distribution. The following research questions will be answered to achieve these objectives: Which applications of drones to urban distribution have been researched? What is the impact of drones on urban distribution in terms of resilience and sustainability? This paper follows a Systematic Literature Review (SLR) approach. The SLR was conducted on the Scopus database and is based on 159 articles. This literature review provides insights into the current state of drone-enhanced urban distribution scientific literature, finds existing gaps and suggests future research opportunities to develop a resilient and sustainable urban distribution system
Modelling the environmental performance of logistics distribution processes: a business case in the agri-food supply chain
Get PDFPurpose – Logistics practitioners face a significant challenge in meeting local and international regulations and the United Nations’ Sustainable Development Goals(SDGs) due to the complexities of measuring and assessing the CO2e emissions of logistics processes. This challenge is pronounced in distribution processes, where the literature currently lacks a structured approach based on existing guidelines and regulations or real-case
implementation examples.
Design/methodology/approach – To analyse the environmental performance of distribution processes, a model with Visual Basic for Applications (VBA) algorithms compliant with the Global Logistics Emissions Council (GLEC) framework was developed. An integrative review identified key elements for evaluating the environmental impact of distribution processes, leading to model development. The model was validated through a business case in the agri-food supply chain, demonstrating its applicability and enabling the analysis of optimisation scenarios.
Findings – The findings suggest potential savings in CO2e emissions of up to 50% by improving vehicle efficiency and maximising vehicle capacity utilisation. Further savings of up to 30% are highlighted for the business case company by increasing intermodal transport modes use.
Originality/value – This study offers several academic and managerial contributions. On the one hand, it offers a structured approach to assess the environmental performance of the logistics distribution processes based on a comprehensive European standard and enriches the literature by providing an industrial application of GLEC framework guidelines. On the other hand, it empowers logistics practitioners with a model to assess the environmental impact of distribution processes, and it enables an enhanced decision making process in selecting transport modes to achieve the company’s sustainability goals
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Ground Segmentation From Large-Scale Terrestrial Laser Scanner Data of Industrial Environments
No full textInmany 3-D perception applications, ground segmentation is a necessary preprocessing phase together with point cloud cleaning and outlier removal. This letter presents a method for ground segmentation in large-scale point clouds of industrial environments acquired using a terrestrial laser scanner (TLS). TLSs provide high-precision, dense 3-D measurements, and therefore, such instruments are becoming the state of the art technology for surveying tasks. In contrast to many previousworks, where ground segmentation has been investigated using a single scan (e.g., in LiDAR-equipped vehicles), experiments have been performed in large-scale point clouds that contain over 1010 points measured from multiple scan stations. The proposed solution is based on a robust estimation of points belonging to the ground below each scan station and it can be applied even in challenging scenarios with nonplanar regions
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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