Oxa[7]superhelicene: A π‐Extended Helical Chromophore Based on Hexa‐peri‐hexabenzocoronenes

A novel π‐extended “superhelicene” based on hexa‐peri‐hexabenzocoronenes (HBCs) has been synthesized by an efficient four‐step synthetic procedure starting from diphenyl ether. Comprehensive structural analysis of the helicene was performed by NMR spectroscopy and mass spectrometry measurements together with X‐ray analysis. Physicochemical analysis of the superhelicene and suitable HBC references revealed it had outstanding fluorescent features with quantum yields of over 80 %.     

Effect of radial-electric-field polarity on wire-array Z-pinch dynamics

The formation of plasma in wire-array Z-pinch experiments was found to depend upon the polarity of the radial-electric field near the wires. Reversing the radial-electric field midway along the length of an array resulted in the ablation rate of one-half of the array being reduced by 50%, significantly delaying the start of its implosion and altering its acceleration towards the axis. The observed phenomena cannot be explained by the standard magnetohydrodynamic models of array behavior, suggesting that effects such as electron emission may be important, especially during wire initiation.     

The role of noise sensitivity in the noise-response relation: a comparison of three international airport studies

In order to examine the role of noise sensitivity in response to environmental noise, this paper presents detailed comparisons of socio-acoustic studies conducted around international airports in Amsterdam, Sydney, and London. Earlier findings that noise sensitivity moderates the effect of noise on annoyance were examined to see if they could be replicated in each of the datasets, independent of the technique of measuring noise sensitivity. The relation between exposure to aircraft noise and noise annoyance was studied separately for groups of individuals with low, medium, and high noise sensitivity, with statistical adjustment for relevant confounders. Results support the previous findings that noise sensitivity is an independent predictor of annoyance and adds to the prediction of noise annoyance afforded by noise exposure level by up to 26% of explained variance. There is no evidence of a moderating effect, whereby the covariation between noise exposure level and annoyance is weak for people who score at the extreme high or low end of the sensitivity scale, and strong for people who score in the middle of the sensitivity scale. Generally, noise sensitivity appears to increase annoyance independently of the level of noise exposure after adjustment for relevant confounders. These findings were consistent across the three datasets.     

Development and intercomparison of a reusable radon-in-water standard

Radium-free standards are not readily available for proficiency testing of laboratories that conduct radon (²²²Rn) analyses of water. For this study, 33 identical, reusable, radon-in-water standards were prepared using a ²²⁶Ra-loaded filter sandwiched in polyethylene sheeting. The ²²²Rn concentrations in the ²²⁶Ra-free standards were measured by liquid scintillation counting and compared to 10 reference solutions containing ²²⁶Ra. The ²²²Rn concentrations measured in the standards were consistent (standard deviation of <2%), but averaged substantially less than concentrations determined in the ²²⁶Ra reference standards. At full ingrowth, 86% of the ²²²Rn produced by the sandwiched ²²⁶Ra sources emanated into the water. An intercomparison of radon-in-water standards, performed to examine the accuracy of analyses by commercial, government, and private companies, showed that 18 of the 21 participants reported concentrations within 25% of the known (693 Bq l^?1).     

Microsecond timescale MD simulations at the transition state of PmHMGR predict remote allosteric residues

Understanding the mechanisms of enzymatic catalysis requires a detailed understanding of the complex interplay of structure and dynamics of large systems that is a challenge for both experimental and computational approaches. More importantly, the computational demands of QM/MM simulations mean that the dynamics of the reaction can only be considered on a timescale of nanoseconds even though the conformational changes needed to reach the catalytically active state happen on a much slower timescale. Here we demonstrate an alternative approach that uses transition state force fields (TSFFs) derived by the quantum-guided molecular mechanics (Q2MM) method that provides a consistent treatment of the entire system at the classical molecular mechanics level and allows simulations at the microsecond timescale. Application of this approach to the second hydride transfer transition state of HMG-CoA reductase from Pseudomonas mevalonii (PmHMGR) identified three remote residues, R396, E399 and L407, (15–27 Å away from the active site) that have a remote dynamic effect on enzyme activity. The predictions were subsequently validated experimentally via site-directed mutagenesis. These results show that microsecond timescale MD simulations of transition states are possible and can predict rather than just rationalize remote allosteric residues.

Transition state force fields enable MD simulations at the transition state of HMGCoA reductase that sample the transition state ensemble on the μs timescale to identify remote residues that affect the reaction rate.