Chasing the “Killer” Phonon Mode for the Rational Design of Low‐Disorder,High‐Mobility Molecular Semiconductors

Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly to the electron–phonon coupling and ensuing thermal energetic disorder in some of the most widely studied high‐mobility molecular semiconductors, state‐of‐the‐art quantum mechanical simulations of the vibrational modes and the ensuing electron–phonon coupling constants are combined with experimental measurements of the low‐frequency vibrations using inelastic neutron scattering and terahertz time‐domain spectroscopy. In this way, the long‐axis sliding motion is identified as a “killer” phonon mode, which in some molecules contributes more than 80% to the total thermal disorder. Based on this insight, a way to rationalize mobility trends between different materials and derive important molecular design guidelines for new high‐mobility molecular semiconductors is suggested.     

Pore‐Scale Flow Characterization of Polymer Solutions in Microfluidic Porous Media

Polymer solutions are frequently used in enhanced oil recovery and groundwater remediation to improve the recovery of trapped nonaqueous fluids. However, applications are limited by an incomplete understanding of the flow in porous media. The tortuous pore structure imposes both shear and extension, which elongates polymers; moreover, the flow is often at large Weissenberg numbers, Wi, at which polymer elasticity in turn strongly alters the flow. This dynamic elongation can even produce flow instabilities with strong spatial and temporal fluctuations despite the low Reynolds number, Re. Unfortunately, macroscopic approaches are limited in their ability to characterize the pore‐scale flow. Thus, understanding how polymer conformations, flow dynamics, and pore geometry together determine these nontrivial flow patterns and impact macroscopic transport remains an outstanding challenge. This review describes how microfluidic tools can shed light on the physics underlying the flow of polymer solutions in porous media at high Wi and low Re. Specifically, microfluidic studies elucidate how steady and unsteady flow behavior depends on pore geometry and solution properties, and how polymer‐induced effects impact nonaqueous fluid recovery. This work thus provides new insights for polymer dynamics, non‐Newtonian fluid mechanics, and applications such as enhanced oil recovery and groundwater remediation.     

Secondhand smoke levels in Scottish pubs: the effect of smoke-free legislation

Objective

To compare levels of particulate matter, as a marker of secondhand smoke (SHS) levels, in pubs before and 2 months after the implementation of Scottish legislation to prohibit smoking in substantially enclosed public places.

Design

Comparison of SHS levels before and after the legislation in a random selection of 41 pubs in 2 Scottish cities.

Methods

Fine particulate matter <2.5 μm in diameter (PM_2.5) was measured discreetly for 30 min in each bar on 1 or 2 visits in the 8 weeks preceding the starting date of the Smoking, Health and Social Care (Scotland) Act 2005 and then again 2 months after the ban. Repeat visits were undertaken on the same day of the week and at approximately the same time of the day.

Results

PM_2.5 levels before the introduction of the legislation averaged 246 μg/m³ (range 8–902 μg/m³). The average level reduced to 20 μg/m³ (range 6–104 μg/m³) in the period after the ban. Levels of SHS were reduced in all 53 post‐ban visits, with the average reduction being 86% (range 12–99%). PM_2.5 concentrations in most pubs post‐ban were comparable to the outside ambient air PM_2.5 level.

Conclusions

This study has produced the largest dataset of pre‐ and post‐ban SHS levels in pubs of all worldwide smoke‐free legislations introduced to date. Our results show that compliance with the Smoking, Health and Social Care (Scotland) Act 2005 has been high and this has led to a marked reduction in SHS concentrations in Scottish pubs, thereby reducing both the occupational exposure of workers in the hospitality sector and that of non‐smoking patrons.Public health policy in a growing number of countries has moved to control non‐smokers'' exposure to secondhand smoke (SHS), with recent legislation introduced in Ireland, Italy, Spain and Norway. The Smoking, Health and Social Care (Scotland) Act 2005 to ban smoking in substantially enclosed public places was implemented on 26 March 2006 with the aim of protecting non‐smokers from the health effects of SHS.¹A recent review of occupational exposure to SHS suggested that workers in the hospitality sector have among the highest exposures to SHS of all occupational groups.² Data on exposure to SHS across a wide range of entertainment establishments indicated that airborne nicotine concentrations were up to 18.5 times higher than in offices or domestic residences.³ Studies have shown that non‐smoking bar workers have salivary cotinine levels four times those of non‐smokers who live with partners who smoke.⁴ Data from New Zealand indicate that non‐smoking hospitality workers in establishments that permit smoking have salivary cotinine levels between 3 and 4 times those of non‐smoking workers in smoke‐free premises.⁵ One estimate indicates that between 1500 and 2000 non‐smokers'' deaths per year in Scotland can be attributed to SHS exposure.⁶ It has been suggested that SHS exposure may lead to the deaths of over 50 hospitality sector workers in the UK each year.⁷The introduction of smoke‐free legislation in other countries has been shown to dramatically reduce SHS levels. A recent analysis of the effect of the Norwegian legislation⁸ showed that total dust levels in 13 bars and restaurants reduced from an average level of 262 to 77 μg/m³, a 70% reduction, whereas a study in the USA indicated that respirable dust levels in a selection of 8 hospitality venues reduced to approximately 9% of the pre‐ban level.⁹ Similar work in New York State in a mixture of bars and restaurants measured levels of particulate matter <2.5 μm in diameter (PM_2.5), and found that mean levels decreased from 412 to 27 μg/m³ (93.5%).¹⁰ Mulcahy et al¹¹ measured changes in airborne nicotine levels as a result of the Irish smoking ban. Their study of 20 pubs showed nicotine reductions of approximately 83%.Although there are currently no air quality standards for PM_2.5 in the UK, both the US Environmental Protection Agency (EPA) and the World Health Organization (WHO) have issued air quality guidance for outdoor air pollution levels measured in PM_2.5.^12,13 The US EPA air quality guidance is divided into bands, and for PM_2.5 these bands are arranged at cut points of <15.4 μg/m³ (good), 15.5–40.4 μg/m³ (moderate), 40.5–65.4 μg/m³ (unhealthy for sensitive groups), 65.5–150.4 μg/m³ (unhealthy), 150.5–250.4 μg/m³ (very unhealthy) and >250.5 μg/m³ (hazardous). The US EPA standard for PM_2.5 has a 24 h averaged target of 65 μg/m³, with an annualised average of 15 μg/m³. The WHO recently revised its outdoor air quality guidance and now recommends a 24 h average limit of 25 μg/m^3, with an annual average not exceeding 10 μg/m³ measured in PM_2.5.¹³This paper describes our methods of measurement of SHS concentrations in a selection of Scottish pubs and examines the changes in SHS levels that occurred as a result of the implementation of the ban on 26 March 2006. It forms part of a comprehensive evaluation strategy to measure the effects of the introduction of the Scottish smoke‐free legislation.¹⁴     

Comparative genomics of the environmental stress response in ascomycete fungi

Unicellular fungi thrive in diverse niches around the world, and many of these niches present unique and stressful challenges that must be contended with by their inhabitants. Numerous studies have investigated the genomic expression responses to environmental stress in 'model' ascomycete fungi, including Saccharomyces cerevisiae, Candida albicans and Schizosaccharomyces pombe. This review presents a comparative-genomics perspective on the environmental stress response, a common response to diverse stresses. Implications for the role of this response, based on its presence or absence in fungi from disparate ecological niches, are discussed.     

Single-particle aerosol mass spectrometry for the detection and identification of chemical warfare agent simulants

Single-particle aerosol mass spectrometry (SPAMS) was used for the real-time detection of liquid nerve agent simulants. A total of 1000 dual-polarity time-of-flight mass spectra were obtained for micrometer-sized single particles each of dimethyl methyl phosphonate, diethyl ethyl phosphonate, diethyl phosphoramidate, and diethyl phthalate using laser fluences between 0.58 and 7.83 nJ/microm2, and mass spectral variation with laser fluence was studied. The mass spectra obtained allowed identification of single particles of the chemical warfare agent (CWA) simulants at each laser fluence used although lower laser fluences allowed more facile identification. SPAMS is presented as a promising real-time detection system for the presence of CWAs.     

Allylamine plasma‐polymerization on PLLA surface evaluation of the biodegradation

Biodegradation of poy(L ‐lactide) (PLLA) films and filaments recovered with hydrophilic layer (contact angle = 14°, surface energy γ_s = 70.9 mJ m^?2) from allylamine plasma polymerization was investigated under aerobic conditions in sludge. XPS and FTIR‐ATR analysis of the plasma layer showed 14.4% N and 16.6% O mainly as amide group. Optical microscopy showed much bacteria colonies on treated PLLA surface than on untreated one. Weight loss and oxygen consumption after 65 days were 4–5% and 4 mg h^?1 per gram polymer respectively. The fact that biodegradation lag‐phase for treated PLLA was released quicker (7 days) than untreated one (14 days), could be related to the presence of hydrophilic plasma layer that improved swelling‐dissolution of hydrolyzed molecular fragments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Silicon analogues of the retinoid agonists TTNPB and 3-methyl-TTNPB, disila-TTNPB and disila-3-methyl-TTNPB: chemistry and biology

Twofold sila-substitution (C/Si exchange) in the saturated ring of the tetrahydronaphthalene skeleton of the retinoid agonists TTNPB (1 a) and 3-methyl-TTNPB (2 a) leads to disila-TTNPB (1 b) and disila-3-methyl-TTNPB (2 b), respectively. The silicon compounds 1 b and 2 b were synthesized in multiple steps, and their identities were established by elemental analyses, multinuclear NMR experiments, and single-crystal X-ray diffraction studies. Like TTNPB (1 a) and 3-methyl-TTNPB (2 a), the analogous silicon-based arotinoids 1 b and 2 b are strong pan-RAR agonists and display the same strong differentiation and apoptosis-inducing activity in NB4 promyelocytic leukemia cells as the parent carbon compounds. These results are in keeping with the nearly isomorphous structures of 1 a and 1 b bound to the complex of the RARbeta ligand-binding domain with the nuclear receptor (NR) box 2 peptide of the SRC-1 coactivator. The contacts within the ligand-binding pocket are identical except for helix H11, for which two turns are shifted in the disila-TTNPB (1 b) complex. This study represents the first comprehensive structure-function analysis of a carbon/silicon switch in a signaling molecule and demonstrates that silicon analogues can have the same biological functionalities and conserved structures as their parent carbon compounds, and it illustrates at the same time that silicon analogues of biologically active compounds have the potential to induce alternative allosteric effects, as in the case of helix H11, which might allow for novel options in drug design.     

Microbial biosorption of copper and lead from aqueous systems

Biosorption of metal ions from aqueous systems was evaluated using a culture of acioic soil isolates grown in a completely mixed, aerobic, semi-batch culture reactor. The laboratory scale system was used to test single and bimetallic solutions of copper and lead with sulfates, chlorides, or nitrates. To elucidate the key factors influencing biosorption and to characterize metal uptake by cellular and extra cellular components of the microbial system, a dialysis testing procedure was developed. A direct contact technique was used to determine the rate of metal sorption on cellular surfaces. The effectiveness of biosorption was influenced by pH, initial metal concentrations, and anionic composition. Respirometric tests were carried out to identify potential inhibitory effects of metal accumulation on microbial oxygen uptake rates.     

Exploiting the Hydrophobic Terrain in Fucosidases with Aryl‐Substituted Pyrrolidine Iminosugars

Fucosidase inhibition shows potential in numerous therapeutic contexts. Substitution of fucose‐like iminosugars with hydrophobic “aglycons” yields significant improvements in potency of fucosidase inhibition. Here we have prepared three new 2‐aryl‐3,4‐dihydroxy‐5‐methylpyrrolidines featuring phenyl substituents in variable orientations with respect to the iminocyclitol core and at various distances from it to explore the key binding interactions that stabilise the enzyme–inhibitor complex. The presence of a triazole linker in one structure resulted in nanomolar inhibition of the fucosidase from bovine kidney (K_i=4.8 nM ), thus giving rise to one of the most potent pyrrolidine‐type inhibitors of this enzyme known to date.