1,721,117 research outputs found
One-electron oxidation and protonation of diferrocenylphenylphosphine
No full textThe one-electron oxidation and protonation of diferrocenylphenylphosphine (Fc2PhP) leads to the formation of two distinct, stable cationic phosphorus species, namely the radical cation [Fc2PhP][B(C6F5)4] and the phosphonium ion [Fc2PhPH][B(C6F5)4]. Although their solid-state structures are remarkably similar, the bathochromic shift in the UV-Vis absorption spectrum of the radical cation, signals with distinct multiplicities in the 31P NMR spectra, as well as contrasting quadrupole splitting values in the 57Fe Mößbauer spectra, elucidated the differences between the two cations
Bayesian approaches to assigning the source of an odour detected by an electronic nose
Full text linkAfter a brief review of electronic nose technology, the use of an Australian electronic nose to identify an unknown odour out of a set of known odours is described. Multivariate supervised learning is accomplished by applying Bayes’ theorem to data from metal oxide semiconductor sensors responding to each of a number of target odours. An odour from an unknown source is then assigned a probability of membership of each of the training sets by applying either a Naïve Bayes algorithm to the deemed independent data from each sensor, or to a multinormal distribution of the data. A flat prior (equal probabilities of each outcome) is usually adopted, but for particular situations where one odour is known to predominate, then suitably weighted priors can be used. A source ‘none of the above’, which has a small likelihood covering the space of the possible sensor responses, is included for completeness. This also avoids the assignment to a source that has an extremely small probability but which is greater than that of any other source. Examples are given of a single source (detecting diabetes from a patient’s breath), and three sources of unpleasant odours in a meat processing plant
Flow-based assembly of nucleic acid-loaded polymer nanoparticles
Full text linkSince the development of messenger RNA (mRNA)-based SARS-CoV-2 (COVID-19) vaccines, there is increased public awareness of the importance of nanoparticles, in this case lipid nanoparticles, to ensure safe delivery of an active compound. To ensure the formation of high-quality nanoparticles with reproducible results, these lipid nanoparticles are assembled with the nucleic acid drug using flow-based devices. Although flow assembly using lipid nanoparticles for nucleic acid delivery is well described in the literature, only a few examples use polymers. This is surprising because the field of polymers for nucleic acid delivery is substantial as hundreds of polymers for nucleic acid delivery have been reported in the literature. In this review, we discuss several aspects of flow-based assembly of nucleic acid-loaded polymer nanoparticles. Initially, we introduce the concept of chip-based or capillary-based systems that can be either used as single-phase or multiphase systems. Initially, researchers have to choose the type of mixing, which can be active or passive. The type of flow, laminar or turbulent, also significantly affects the quality of the nanoparticles. We then present the type of polymers that have so far been assembled with mRNA, small interfering RNA (siRNA) or plasmid DNA (pDNA) using flow devices. We discuss effects such as flow rate, concentration and polymer lengths on the outcome. To conclude, we highlight how flow assembly is an excellent way to generate well-defined nanoparticles including polyplexes in a reproducible manner
A potentially polymerizable heterodinuclear FeIIIZnII purple acid phosphatase mimic. Synthesis, characterization, and phosphate ester hydrolysis studies
No full textAn analogue of the purple acid phosphatase biomimetic 2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-(((2-hydroxybenzyl)(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol has been synthesized. The analogue, 2-((bis(pyridin-2-ylmethyl)amino)methyl)-6-(((2-hydroxy-4-(4-vinylbenzyloxy)benzyl)(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol (H2BPBPMPV) possesses a pendant olefin suitable for copolymerization. Complexation with Fe-III/Zn-II resulted in the complex [(FeZnII)-Zn-III (BPBPMPV)(CH3COO)(2)](ClO4), characterized with mass spectrometry, microanalysis, UV/vis, and IR spectrometry. The catalytic activity of the complex toward bis-(2,4-dinitrophenyl) phosphate was determined, resulting in K-m of 4.1 +/- 0.6 mM, with k(cat) 3.8 +/- 0.2 x 10(-3) s(-1) and a bell-shaped pH-rate profile with pK(a) values of 4.31, 5.66, 8.96, the profile exhibiting residual activity above pH 9.5
Self-assembled monolayers: a journey from fundamental tools for understanding interfaces to commercial sensing technologies
Full text linkSelf-assembled monolayers were first described in the 1980s and have now become ubiquitous in many interfacial technologies. In this account, we discuss different self-assembled monolayer systems, outlining their positives and negatives. We then overview other researchers’ work and our own group’s journey in using self-assembled monolayers to develop new concepts in sensing and addressing general challenges faced by many types of sensors. Finally, we reflect on some of the challenges monolayer chemistry needs to address to facilitate further use of this powerful surface chemistry in commercial devices
Cobalt oxide-based catalysts for acidic oxygen evolution reactions
No full textProton exchange membrane water electrolysis (PEMWE) is a cornerstone technology for green hydrogen production, yet the sluggish oxygen evolution reaction (OER) in acidic media remains a major bottleneck. Noble metal oxides such as IrO2 and RuO2 are effective but suffer from high cost and scarcity. As a non-precious alternative, spinel cobalt oxide (Co3O4) has attracted attention due to its promising performance results from its mixed-valence structure, tunable electronic properties and catalytic potential. However, its practical application is challenged by poor conductivity, moderate activity and instability under acidic conditions due to proton attack and lattice degradation. This review summarises recent advances in Co3O4-based electrocatalysts for acidic OER. We first introduce three key OER pathways: adsorbate evolution mechanism (AEM), lattice oxygen mechanism (LOM) and oxide path mechanism (OPM) and their relevance to Co3O4 performance. Then, we introduce the structural and electronic characteristics of Co3O4 that influence its catalytic behaviour. Next, we review a range of engineering strategies, including element doping, heterostructure construction, surface modification and defect engineering, all aimed at enhancing the activity and durability of Co3O4. Finally, we highlight critical challenges and offer perspectives for advancing Co3O4 as a viable acidic OER catalyst
HFIP-assisted Brønsted acid catalysed synthesis of furan derivatives
Full text linkThe furan framework is ubiquitous in naturally occurring compounds, and furan-containing
structures are also key intermediates to many industrially important chemicals and materials.
There have been reports of numerous methods to synthesise furans, however most of them
use transition metal catalysts or Brønsted acid catalysts under harsh conditions. This work
describes the development of a new non-metal Brønsted acid catalytic method for the synthesis
of 2-aryl-3-carboxylate ester furans and 2,3-diaryl furans from ynone substrates. The method was
shown to be efficient under very mild reaction conditions with up to 94% product yield
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
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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