Literature Review of Radical-Polar Crossover Reaction

Described are Radical-Polar Crossover (RPC) reactions, which have played an important role in the organic synthesis, but very few review articles previously mentioned this concept. Using both photoredox catalysis and non-photoredox catalysis can achieve the RPC transformation within a one-pot mechanism under very mild condition. Besides this, RPC reactions provide many practical advantages such as rapid increasing in molecular complexity and good functional group tolerance. Therefore, this potentially valuable reaction can provide a lot of research opportunities. Overall, the comparison of different authors’ views, critical analyses of the methods, and an overall summary of the literature will be described in this review. The purpose of this work is to narrate both photoredox RPC reactions and non-photoredox RPC reactions in a systematic fashion and to grasp the valuable point of view from different authors. Applications of RPC reactions to the pharmaceutical sciences and industry will be presented at the end

Challenges in Exposure Modeling of Nanoparticles in Aquatic Environments

Managing the potential environmental risks of nanoparticles requires methods to link nanoparticle properties with macro-scale risks. This study outlines challenges in exposure modeling of nanoparticles in aquatic environments, such as the role of natural organic matter, natural colloids, fractal dimensions of agglomerates, coatings and doping of particles, and uncertainties regarding nanoparticle emissions to aquatic environments. The pros and cons of the exposure indicators mass concentration, particle number concentration, and surface area are discussed. By applying colloid chemistry kinetic equations describing particle agglomeration and sedimentation for the case of titanium dioxide nanoparticles, a limited exposure assessment including some of the factors mentioned is conducted with particle number concentration as the exposure indicator. The results of the modeling indicate that sedimentation, shear flows, and settling are of less importance with regard to particle number based predicted environmental concentrations. The inflow of nanoparticles to the water compartment had a significant impact in the model, and the collision efficiency (which is affected by natural organic matter) was shown to greatly affect model output. Implications for exposure modeling, regulation and science are discussed. A broad spectrum of scientific disciplines must be engaged in the development of exposure models where nano-level properties are linked to macro-scale risk

How to make policy-relevant life cycle assessments of future products? Lessons learned from nanomaterials

Many new nanomaterials are currently being developed, and there is a great demand from policy-makers such as governments and agencies to understand the future environmental impact of nanomaterials. However, assessing the life cycle environmental impacts, e.g. in terms of emissions and energy use, related to these materials and products that contain them constitutes a great challenge, which makes it difficult to meet such needs from policy-makers. The challenge is much due to the many uncertainties that surround new nanomaterials at an early point of technological development, which makes environmental assessment methods such as life cycle assessment difficult to apply. These uncertainties include the future areas of application of the nanomaterial, future designs of products within those areas, and future production processes. When one or more of these uncertainties are present, we say that the life cycle or product chain is embryonic. This embryonic nature of nanomaterial life cycles differentiates them from the life cycles of more established products, such as cups and cucumbers. Assessing the environmental impacts of embryonic nanomaterial life cycles requires the assessor to understand the future, or rather some aspects of a number of possible futures. Hence, we need to make use of methods belonging to the field of future studies, including monitoring of trends in technology development (e.g. via patent analysis) and application areas as well as predicting and exploring by trend analysis, expert judgement, and sometimes even fantasizing. We illustrate the theoretical concept of embryonic life cycles with a number of examples of embryonic nanomaterial life cycles, including carbon nanotubes in composites, titanium dioxide nanoparticles in self-cleaning cement and graphene in electronic devices and composites. We show that a range of future study approaches may enrich, or even be essential to, policy-relevant life cycle assessments. We also show that environmental assessments such as life cycle assessment can be misused or used in questionable ways when applied to embryonic life cycles with the purpose of obtaining policy-relevant results

Prospective Life Cycle Assessment of Graphene Production by Ultrasonication and Chemical Reduction

One promising future bulk application of graphene is as composite additive. Therefore, we compare two production routes for insolution graphene using a cradle-to-gate lifecycle assessment focusing on potential differences in energy use, blue water footprint, human toxicity, and ecotoxicity. The data used for the assessment is based on information in scientific papers and patents. Considering the prospective nature of this study, environmental impacts from background systems such as energy production were not included. The production routes are either based on ultrasonication or chemical reduction. The results show that the ultrasonication route has lower energy and water use, but higher human and ecotoxicity impacts, compared to the chemical reduction route. However, a sensitivity analysis showed that solvent recovery in the ultrasonication process gives lower impacts for all included impact categories. The sensitivity analysis also showed that solvent recovery is important to lower the blue water footprint of the chemical reduction route as well. The results demonstrate the possibility to conduct a life cycle assessment study based mainly on information from patents and scientific articles, enabling prospective life cycle assessment studies of products at early stages of technological development

Expertise, policy-making and democracy

This book offers a concise and accessible introduction to debates about expertise, policy-making and democracy. It uniquely combines an overview of recent research on the policy role of experts with discussions in political philosophy and the philosophy of expertise. Starting with the fact that well-functioning democracies require experts and expert knowledge, the book examines two types of objections against granting experts a larger role in policy-making: concerns that focus on the nature and limits of expert knowledge, and those that concentrate on tensions between expertization and democracy. With this, the book discusses how expert arrangements can be organized to ensure the epistemic qualities of policies and democratic credentials, at the same time.The book will be of interest to scholars and students of political theory and democracy, public policy and administration, and to anyone interested in the role of expertise in society.The politics and administration of institutional chang

The upgraded ISOLDE yield database - A new tool to predict beam intensities

At the CERN-ISOLDE facility a variety of radioactive ion beams are available to users of the facility. The number of extractable isotopes estimated from yield database data exceeds 1000 and is still increasing. Due to high demand and scarcity of available beam time, precise experiment planning is required. The yield database stores information about radioactive beam yields and the combination of target material and ion source needed to extract a certain beam along with their respective operating conditions. It allows to investigate the feasibility of an experiment and the estimation of required beamtime. With the increasing demand for ever more exotic beams, needs arise to extend the functionality of the database and website not only to provide information about yields determined experimentally, but also to predict yields of isotopes, which can only be measured with sophisticated setups. For the prediction of yields, in-target production and information about release properties of target materials must be known. While the former were estimated in a simulation campaign using FLUKA and ABRABLA codes, the latter is available from measurement data as already stored in the database. We have compiled the information necessary to predict yields, and made available a yield prediction tool as web application. This currently undergoes extensive testing and will be available as powerful tool to the ISOLDE user community.Peer reviewe

Superradiance from an ultrathin film of three-level V-type atoms: Interplay between splitting, quantum coherence and local-field effects

We carry out a theoretical study of the collective spontaneous emission (superradiance) from an ultrathin film comprised of three-level atoms with $V$-configuration of the operating transitions. As the thickness of the system is small compared to the emission wavelength inside the film, the local-field correction to the averaged Maxwell field is relevant. We show that the interplay between the low-frequency quantum coherence within the subspace of the upper doublet states and the local-field correction may drastically affect the branching ratio of the operating transitions. This effect may be used for controlling the emission process by varying the doublet splitting and the amount of low-frequency coherence.Comment: 15 pages, 5 figure

Neutral and Cationic Rare Earth Metal Alkyl and Benzyl Compounds with the 1,4,6-Trimethyl-6-pyrrolidin-1-yl-1,4-diazepane Ligand and Their Performance in the Catalytic Hydroamination/Cyclization of Aminoalkenes

A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L) was prepared. Reacting L with trialkyls M(CH2SiMe3)3(THF)2 (M = Sc, Y) and tribenzyls M(CH2Ph)3(THF)3 (M = Sc, La) yielded trialkyl complexes (L)M(CH2SiMe3)3 (M = Sc, 1; M = Y, 2) and tribenzyl complexes (L)M(CH2Ph)3 (M = Sc, 3; M = La, 4). Complexes 1 and 2 can be converted to their corresponding ionic compounds [(L)M(CH2SiMe3)2(THF)][B(C6H5)4] (M = Sc, Y) by reaction with [PhNMe2H][B(C6H5)4] in THF. Complexes 3 and 4 can be converted to cationic species [(L)M(CH2Ph)2]+ by reaction with [PhNMe2H][B(C6F5)4] in C6D5Br in the absence of THF. The neutral complexes 1-4 and their cationic derivatives were studied as catalysts for the hydroamination/cyclization of 2,2-diphenylpent-4-en-1-amine and N-methylpent-4-en-1-amine reference substrates and compared with ligand-free Sc, Y, and La neutral and cationic catalysts. The most effective catalysts in the series were the cationic L-yttrium catalyst (for 2,2-diphenylpent-4-en-1-amine) and the cationic lanthanum systems (for N-methylpent-4-en-1-amine). For the La catalysts, evidence was obtained for release of L from the metal during catalysis.

Classical Evolution of Quantum Elliptic States

The hydrogen atom in weak external fields is a very accurate model for the multiphoton excitation of ultrastable high angular momentum Rydberg states, a process which classical mechanics describes with astonishing precision. In this paper we show that the simplest treatment of the intramanifold dynamics of a hydrogenic electron in external fields is based on the elliptic states of the hydrogen atom, i.e., the coherent states of SO(4), which is the dynamical symmetry group of the Kepler problem. Moreover, we also show that classical perturbation theory yields the {\it exact} evolution in time of these quantum states, and so we explain the surprising match between purely classical perturbative calculations and experiments. Finally, as a first application, we propose a fast method for the excitation of circular states; these are ultrastable hydrogenic eigenstates which have maximum total angular momentum and also maximum projection of the angular momentum along a fixed direction. %Comment: 8 Pages, 2 Figures. Accepted for publication in Phys. Rev.