Data Mining - Concepts and Techniques.

How to Do Things With Words

Global energy consumption is projected to increase, even in the face of substantial declines in energy intensity, at least 2-fold by midcentury relative to the present because of population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of CO2 emissions in the atmosphere demands that holding atmospheric CO2 levels to even twice their preanthropogenic values by midcentury will require invention, development, and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable energy resources, solar energy is by far the largest exploitable resource, providing more energy in 1 hour to the earth than all of the energy consumed by humans in an entire year. In view of the intermittency of insolation, if solar energy is to be a major primary energy source, it must be stored and dispatched on demand to the end user. An especially attractive approach is to store solar-converted energy in the form of chemical bonds, i.e., in a photosynthetic process at a year-round average efficiency significantly higher than current plants or algae, to reduce land-area requirements. Scientific challenges involved with this process include schemes to capture and convert solar energy and then store the energy in the form of chemical bonds, producing oxygen from water and a reduced fuel such as hydrogen, methane, methanol, or other hydrocarbon species.

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Powering the planet: Chemical challenges in solar energy utilization

語用論(Pragmatics)を考える

The site-selective formation of carbon-carbon bonds through direct functionalizations of otherwise unreactive carbon-hydrogen bonds constitutes an economically attractive strategy for an overall streamlining of sustainable syntheses. In recent decades, intensive research efforts have led to the development of various reaction conditions for challenging C-H bond functionalizations, among which transition-metal-catalyzed transformations arguably constitute thus far the most valuable tool. For instance, the use of inter alia palladium, ruthenium, rhodium, copper, or iron complexes set the stage for chemo-, site-, diastereo-, and/or enantioselective C-H bond functionalizations. Key to success was generally a detailed mechanistic understanding of the elementary C-H bond metalation step, which depending on the nature of the metal fragment can proceed via several distinct reaction pathways. Traditionally, three different modes of action were primarily considered for CH bond metalations, namely, (i) oxidative addition with electronrich late transition metals, (ii) σ-bond metathesis with early transition metals, and (iii) electrophilic activation with electrondeficient late transition metals (Scheme 1). However, more recent mechanistic studies indicated the existence of a continuum of electrophilic, ambiphilic, and nucleophilic interactions. Within this continuum, detailed experimental and computational analysis provided strong evidence for novel C-H bond metalationmechanisms relying on the assistance of a bifunctional ligand bearing an additional Lewis-basic heteroatom, such as that found in (heteroatom-substituted) secondary phosphine oxides or most prominently carboxylates (Scheme 1, iv). This novel insight into the nature of stoichiometric metalations has served as stimulus for the development of novel transformations based on cocatalytic amounts of carboxylates, which significantly broadened the scope of C-H bond functionalizations in recent years, with most remarkable progress being made in palladiumor ruthenium-catalyzed direct arylations and direct alkylations. These carboxylate-assisted C-H bond transformations were mostly proposed to proceed via a mechanism in which metalation takes place via a concerted base-assisted deprotonation. To mechanistically differentiate these intramolecular metalations new acronyms have recently been introduced into the literature, such as CMD (concerted metalationdeprotonation), IES (internal electrophilic substitution), or AMLA (ambiphilic metal ligand activation), which describe related mechanisms and will be used below where appropriate. This review summarizes the development and scope of carboxylates as cocatalysts in transition-metal-catalyzed C-H functionalizations until autumn 2010. Moreover, experimental and computational studies on stoichiometric metalation reactions being of relevance to the mechanism of these catalytic processes are discussed as well. Mechanistically related C-H bond cleavage reactions with ruthenium or iridium complexes bearing monodentate ligands are, however, only covered with respect to their working mode, and transformations with stoichiometric amounts of simple acetate bases are solely included when their mechanism was suggested to proceed by acetate-assisted metalation.

Carboxylate-assisted transition-metal-catalyzed C-H bond functionalizations: mechanism and scope.

Crystallization of Na2VOP2O7 from its aqueous solution results in formation of a one-dimensional inorganic polymer {Na2VO(H2O)P2O7·7H2O}n (1). When this polymer is dehydrated at elevated temperatures this polymer undergoes a phase transition to form the two-dimensional framework β-Na2VOP2O7, which although previously reported had been difficult to access. Exchanging lithium for sodium via ion-exchange chromatography results in formation of a discrete, cyclic, tetramer species, Li8[VOP2O7(H2O)·4H2O]4 (2). Isolation of crystalline β-Li2VOP2O7 using a dehydration procedure analogous to the one employed for the sodium derivative was unsuccessful. In contrast, we show that β-K2VOP2O7 can be obtained from the amorphous phase K2VOP2O7·nH2O (n = 0–7) upon thermal dehydration.

Facile Synthesis of Zero-, One-, and Two-Dimensional Vanadyl Pyrophosphates.

Herein is reported the structural characterization and scalable preparation of the elusive iron–phosphido complex FpP(tBu)(F) (2-F, Fp = (Fe(η5-C5H5)(CO)2)) and its precursor FpP(tBu)(Cl) (2-Cl) in 51% and 71% yields, respectively. These phosphide complexes are proposed to be relevant to an organoiron catalytic cycle for phosphinidene transfer to electron-deficient alkenes. Examination of their properties led to the discovery of a more efficient catalytic system involving the simple, commercially available organoiron catalyst Fp2. This improved catalysis also enabled the preparation of new phosphiranes with high yields (tBuPCH2CHR; R = CO2Me, 41%; R = CN, 83%; R = 4-biphenyl, 73%; R = SO2Ph, 71%; R = POPh2, 70%; R = 4-pyridyl, 82%; R = 2-pyridyl, 67%; R = PPh3+, 64%) and good diastereoselectivity, demonstrating the feasibility of the phosphinidene group-transfer strategy in synthetic chemistry. Experimental and theoretical studies suggest that the original catalysis involves 2-X as the nucleophile, while for the new Fp2-catalyzed reaction they implicate a diiron–phosphido complex Fp2(PtBu), 4, as the nucleophile which attacks the electron-deficient olefin in the key first P–C bond-forming step. In both systems, the initial nucleophilic attack may be accompanied by favorable five-membered ring formation involving a carbonyl ligand, a (reversible) pathway competitive with formation of the three-membered ring found in the phosphirane product. A novel radical mechanism is suggested for the new Fp2-catalyzed system.

Synthesis of phosphiranes via organoiron-catalyzed phosphinidene transfer to electron-deficient olefins

Language relies on theory of mind, as language users have to entertain and recognise communicative intentions (e.g. Moore, 2016; Scott-Philips, 2014). Theory of mind abilities in turn profit from language, as language provides a means for expressing mental states explicitly (e.g. Bar-On, 2013), and for transmitting one’s understanding of minds to others (e.g. younger members of the population) (Heyes & Frith, 2014). Given this interdependence, it has been hypothesised that language and theory of mind have co-evolved (e.g. Malle, 2002). We present an agent-based model to formalise this hypothesis, which builds on a model described in Woensdregt, Kirby, Cummins, and Smith (2016). This model focuses on the ability to take others’ perspectives, which is part of (the development of) theory of mind (e.g. Apperly, 2011), and has a clear and concrete role to play in everyday referential signalling (e.g. Clark & Wilkes-Gibbs, 1986). In this model, the communicative behaviour of an agent is determined not just by their language but also by their perspective on the world. Each agent has a perspective which, in interaction with a given context, determines the salience of potential topics to them. Because all objects in the world are considered potential topics, learners have no other way of inferring the intended referent of an utterance than by gaining knowledge of the speaker’s perspective and lexicon (i.e. crosssituational learning is not possible). However, neither a speaker’s perspective nor their lexicon are directly observable. Learners thus have to infer both of these simultaneously, using Bayesian inference. Simulation results show that learners can solve this task by bootstrapping one from the other, but only if the speaker uses a language that is at least somewhat informative (Woensdregt et al., 2016). Given this model of how an agent’s perspective in combination with a context gives rise to a mental state, we can compare two different types of agents. Literal agents choose an utterance purely based on whether or not the signal is associated with the intended referent in their lexicon. A listener then interprets the utterance by inverting this speaker model (using the lexicon and perspective hypothesis they selected for this speaker after a learning phase). Listeners of this type thus use their perspective-taking ability for interpreting utterances, but literal speakers do 531

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A model of cultural co-evolution of language and perspectivetaking

Constraint-based approaches to pragmatics have customarily focused on the hearer, and offered accounts of the optimal interpretation of utterances. Blutner 2006, i.a. has argued that it is necessary also to consider the role of the speaker, and thus motivates a bidirectional Optimality Theory OT approach to pragmatics. However, as he notes, this may have limited explanatory potential from a processing viewpoint. A recent account, focusing on expressions of quantity, aims instead to model the speaker's choice of expression by means of unidirectional OT mechanisms. In this paper I discuss the merits of this approach versus OT-based alternatives. In particular, I explore the implications of this account for the hearer, who is required to solve the problem of utterance interpretation in a non-OT fashion in this model, and explore how this task can be made tractable. I briefly discuss the novel predictions about interpretation and processing that arise from such a development, and consider the theoretical implications for pragmatics in general.

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A Speaker-Referring OT Pragmatics of Quantity Expressions

Dihydrogen metaphosphate can be synthesized via protonation, and can react with a dehydrating agent to afford tetrametaphosphate anhydride. A monohydrogen tetra-metaphosphate organic ester can be derived from the anhydride. A metal tetrametaphosphate complex can be prepared using a metal salt and a dihydrogen tetrametaphosphate.

Christopher C. Cummins

Papers

Facile Synthesis of Zero-, One-, and Two-Dimensional Vanadyl Pyrophosphates.

Synthesis of phosphiranes via organoiron-catalyzed phosphinidene transfer to electron-deficient olefins

A model of cultural co-evolution of language and perspectivetaking

A Speaker-Referring OT Pragmatics of Quantity Expressions

Dihydrogen tetrametaphosphate, its derivatives, and preparation thereof