4-π-Photocyclization of 1,2-Dihydropyridazines: An Approach to Bicyclic 1,2-Diazetidines with Rich Synthetic Potential.

The 4-π-photocyclization of a range of 1,2-dihydropyridazines is described, generating bicyclic 1,2-diazetidines in high yields on multigram scale. The key bicyclic 1,2-diazetidines are versatile synthetic intermediates and were easily converted into a range of novel derivatives, including functionalized 1,2-diazetidines, cyclobutenes, cyclobutanes, and 1,3-dienes

Dirac spinor fields in the teleparallel gravity: comment on "Metric-affine approach to teleparallel gravity"

We show that the coupling of a Dirac spinor field with the gravitational field in the teleparallel equivalent of general relativity is consistent. For an arbitrary SO(3,1) connection there are two possibilities for the coupling of the spinor field with the gravitational field. The problems of consistency raised by Y. N. Obukhov and J. G. Pereira in the paper {\it Metric-affine approach to teleparallel gravity} [gr-qc/0212080] take place only in the framework of one particular coupling. By adopting an alternative coupling the consistency problem disappears.Comment: 8 pages, Latex file, no figures, to appear in the Phys. Rev. D as a Commen

Molecule‐Induced Radical Formation (MIRF) Reactions—A Reappraisal

Radical chain reactions are commonly initiated through the thermal or photochemical activation of purpose‐built initiators, through photochemical activation of substrates, or through well‐designed redox processes. Where radicals come from in the absence of these initiation strategies is much less obvious and are often assumed to derive from unknown impurities. In this situation, molecule‐induced radical formation (MIRF) reactions should be considered as well‐defined alternative initiation modes. In the most general definition of MIRF reactions, two closed‐shell molecules react to give a radical pair or biradical. The exact nature of this transformation depends on the σ‐ or π‐bonds involved in the MIRF process, and this Minireview specifically focuses on reactions that transform two σ‐bonds into two radicals and a closed‐shell product molecule

RAFT-based polystyrene and polyacrylate melts under thermal and mechanical stress

Although controlled/living radical polymerization processes have significantly facilitated the synthesis of well-defined low polydispersity polymers with specific functionalities, a detailed and systematic knowledge of the thermal stability of the products-highly important for most industrial processes-is not available. Linear polystyrene (PS) carrying a trithiocarbonate mid-chain functionality (thus emulating the structure of the Z-group approach via reversible addition-fragmentation chain transfer (RAFT) based macromolecular architectures) with various chain lengths (20 kDa ≤ Mn,SEC ≤ 150 kDa, 1.27 ≤ Crossed D sign = Mw/Mn ≤ 1.72) and chain-end functionality were synthesized via RAFT polymerization. The thermal stability behavior of the polymers was studied at temperatures ranging from 100 to 200 C for up to 504 h (3 weeks). The thermally treated polymers were analyzed via size exclusion chromatography (SEC) to obtain the dependence of the polymer molecular weight distribution on time at a specific temperature under air or inert atmospheres. Cleavage rate coefficients of the mid-chain functional polymers in inert atmosphere were deduced as a function of temperature, resulting in activation parameters for two disparate Mn starting materials (Ea = 115 ± 4 kJ·mol-1, A = 0.85 × 109 ± 1 × 109 s-1, M n,SEC = 21 kDa and Ea = 116 ± 4 kJ·mol -1, A = 6.24 × 109 ± 1 × 109 s-1, Mn,SEC = 102 kDa). Interestingly, the degradation proceeds significantly faster with increasing chain length, an observation possibly associated with entropic effects. The degradation mechanism was explored in detail via SEC-ESI-MS for acrylate based polymers and theoretical calculations suggesting a Chugaev-type cleavage process. Processing of the RAFT polymers via small scale extrusion as well as a rheological assessment at variable temperatures allowed a correlation of the processing conditions with the thermal degradation properties of the polystyrenes and polyacrylates in the melt. © 2013 American Chemical Society.C.B.-K and M.W. gratefully acknowledge financial support from the German Research Council (DFG). M.L.C gratefully acknowledges generous allocations of supercomputing time from the Australian National Computing Facility, financial support from the Australian Research Council (ARC) Centre of Excellence for Free-radical Chemistry and Biotechnology and an ARC Future Fellowship. C.B.-K. acknowledges additional funding from the Karlsruhe Institute of Technology (KIT) in the context of the Helmholtz programs

Separating Convective from Diffusive Mass Transport Mechanisms in Ionic Liquids by Redox Pro-fluorescence Microscopy

The study of electrochemical reactivity requires analytical techniques capable of probing the diffusion of reactants and products to and from electrified interfaces. Information on diffusion coefficients is often obtained indirectly by modeling current transients and cyclic voltammetry data, but such measurements lack spatial resolution and are accurate only if mass transport by convection is negligible. Detecting and accounting for adventitious convection in viscous and wet solvents, such as ionic liquids, is technically challenging. We have developed a direct, spatiotemporally resolved optical tracking of diffusion fronts which can detect and resolve convective disturbances to linear diffusion. By tracking the movement of an electrode-generated fluorophore, we demonstrate that parasitic gas evolving reactions lead to 10-fold overestimates of macroscopic diffusion coefficients. A hypothesis is put forward linking large barriers to inner-sphere redox reactions, such as hydrogen gas evolution, to the formation of cation-rich overscreening and crowding double layer structures in imidazolium-based ionic liquids

Disubstituted Aminoanthraquinone-Based Multicolor Photoinitiators: Photoinitiation Mechanism and Ability of Cationic Polymerization under Blue, Green, Yellow, and Red LEDs

The investigation and clarification of the photoinitiation mechanism of novel systems are of importance for the design and development of compounds with high photoinitiation efficiency of photopolymerization. Some disubstituted aminoanthraquinone derivatives have been reported to exhibit interesting photochemical/photophysical properties and have the potential to act as high performance multicolor photoinitiators under the irradiation of various wavelengths of visible light from light-emitting diodes (LEDs). Herein, three disubstituted aminoanthraquinone derivatives, i.e., 1-amino-4-hydroxyanthraquinone, 1,4-diaminoanthraquinone, and 1,5-diaminoanthraquinone, with iodonium salt and N-vinylcarbazole as additives, have been investigated. Their photoinitiation mechanism was studied using fluorescence spectroscopy, laser flash photolysis, steady state photolysis, computational quantum chemistry, and electron spin resonance spin trapping techniques. Then, their photoinitiation ability for the cationic photopolymerization of epoxide and divinyl ether monomers under the irradiation of diverse LEDs (i.e., blue, green, yellow, and red LEDs) was investigated. The types and positions of substituents were found to play a vital role in the photoreactivity and photoinitiation ability of the disubstituted aminoanthraquinone derivative-based photoinitiating systems.P.X. acknowledges funding from the Australian Research Council Future Fellowship (FT170100301). M.L.C. gratefully acknowledges a Georgina Sweet ARC Laureate Fellowship (FL170100041) and generous allocations of supercomputing time on the National Facility of the Australian National Computational Infrastructur

Mothers behaving badly: chaotic hedonism and the crisis of neoliberal social reproduction

This article focuses on the significance of the plethora of representations of mothers ‘behaving badly’ in contemporary anglophone media texts, including the films Bad Moms, Fun Mom Dinner and Bad Mom’s Christmas, the book and online cartoons Hurrah for Gin and the recent TV comedy dramas Motherland, The Let Down and Catastrophe. All these media texts include representations of, first, mothers in the midst of highly chaotic everyday spaces where any smooth routine of domesticity is conspicuous by its absence; and second, mothers behaving hedonistically, usually through drinking and partying, behaviour that is more conventionally associated with men or women without children. After identifying the social type of the mother behaving badly (MBB), the article locates and analyses it in relation to several different social and cultural contexts. These contexts are: a neoliberal crisis in social reproduction marked by inequality and overwork; the continual if contested role of women as ‘foundation parents’; and the negotiation of longer-term discourses of female hedonism. The title gestures towards a popular British sitcom of the 1990s, Men Behaving Badly, which popularized the idea of the ‘new lad’; and this article suggests that the new lad’s counterpart, the ladette, is mutating into the mother behaving badly, or the ‘lad mom’. Asking what work this figure does now, in a later neoliberal context, it argues that the mother behaving badly is simultaneously indicative of a widening and liberating range of maternal subject positions and symptomatic of a profound contemporary crisis in social reproduction. By focusing on the classed and racialised dynamics of the MBB – by examining who exactly is permitted to be hedonistic, and how – and by considering the MBB’s limited and partial imagining of progressive social change, the article concludes by emphasizing the urgency of creating more connections between such discourses and ‘parents behaving politically’

Development of Modeling Approaches for Nuclear Thermal Propulsion Test Facilities

No abstract availabl

Labetalol Versus Nifedipine as Antihypertensive Treatment for Chronic Hypertension in Pregnancy: A Randomized Controlled Trial

Data from randomized controlled trials to guide antihypertensive agent choice for chronic hypertension in pregnancy are limited; this study aimed to compare labetalol and nifedipine, additionally assessing the impact of ethnicity on treatment efficacy. Pregnant women with chronic hypertension (12+0-27+6 weeks' gestation) were enrolled at 4 UK centers (August 2014 to October 2015). Open-label first-line antihypertensive treatment was randomly assigned: labetalol- (200-1800 mg/d) or nifedipine-modified release (20-80 mg/d). Analysis included 112 women (98%) who completed the study (labetalol n=55, nifedipine n=57). Maximum blood pressure after randomization was 161/101 mm Hg with labetalol versus 163/105 mm Hg with nifedipine (mean difference systolic: 1.2 mm Hg [-4.9 to 7.2 mm Hg], diastolic: 3.3 mm Hg [-0.6 to 7.3 mm Hg]). Mean blood pressure was 134/84 mm Hg with labetalol and 134/85 mm Hg with nifedipine (mean difference systolic: 0.3 mm Hg [-2.8 to 3.4 mm Hg], and diastolic: -1.9 mm Hg [-4.1 to 0.3 mm Hg]). Nifedipine use was associated with a 7.4-mm Hg reduction (-14.4 to -0.4 mm Hg) in central aortic pressure, measured by pulse wave analysis. No difference in treatment effect was observed in black women (n=63), but a mean 4 mm Hg reduction (-6.6 to -0.8 mm Hg; P=0.015) in brachial diastolic blood pressure was observed with labetalol compared with nifedipine in non-black women (n=49). Labetalol and nifedipine control mean blood pressure to target in pregnant women with chronic hypertension. This study provides support for a larger definitive trial scrutinizing the benefits and side effects of first-line antihypertensive treatment. CLINICAL TRIAL REGISTRATION: URL: https://www.isrctn.com. Unique identifier: ISRCTN40973936

Discrete and Stereospecific Oligomers Prepared by Sequential and Alternating Single Unit Monomer Insertion

Natural biopolymers, such as DNA and proteins, have uniform microstructures with defined molecular weight, precise monomer sequence, and stereoregularity along the polymer main chain that affords them unique biological functions. To reproduce such structurally perfect polymers and understand the mechanism of specific functions through chemical approaches, researchers have proposed using synthetic polymers as an alternative due to their broad chemical diversity and relatively simple manipulation. Herein, we report a new methodology to prepare sequence-controlled and stereospecific oligomers using alternating radical chain growth and sequential photoinduced RAFT single unit monomer insertion (photo-RAFT SUMI). Two families of cyclic monomers, the indenes and the N-substituted maleimides, can be alternatively inserted into RAFT agents, one unit at a time, allowing the monomer sequence to be controlled through sequential and alternating monomer addition. Importantly, the stereochemistry of cyclic monomer insertion into the RAFT agents is found to be trans-selective along the main chains due to steric hindrance from the repeating monomer units. All investigated cyclic monomers provide such trans-selectivity, but analogous acyclic monomers give a mixed cis- and trans-insertion