Electronic Visualisation in Chemistry: From Alchemy to Art

Chemists now routinely use software as part of their work. For example, virtual chemistry allows chemical reactions to be simulated. In particular, a selection of software is available for the visualisation of complex 3-dimensional molecular structures. Many of these are very beautiful in their own right. As well as being included as illustrations in academic papers, such visualisations are often used on the covers of chemistry journals as artistically decorative and attractive motifs. Chemical images have also been used as the basis of artworks in exhibitions. This paper explores the development of the relationship of chemistry, art, and IT. It covers some of the increasingly sophisticated software used to generate these projections (e.g., UCSF Chimera) and their progressive use as a visual art form.Comment: 8 pages, 27 figures, EVA London 201

End User Query Performance: The Interaction of User Characteristics and Information Request Ambiguity

This paper investigates the effects of personality characteristics on individuals’ abilities to resolve ambiguity in an information retrieval environment. In particular, this research examines the effects on query performance of the interaction of personality characteristics (as measured using the NEO PI-R) with information requests that contained extraneous, syntactic, or both extraneous and syntactic ambiguities. The results indicate that ambiguity affected performance. The results also show that various personality dimensions significantly affect end-users’ abilities to compose accurate queries. Neuroticism, agreeableness, openness to experience, and conscientiousness affected the number of errors made in the query formulations. Conscientiousness affected the length of time taken to compose the queries and neuroticism affected the confidence end users had in the accuracy of their queries. In addition, the results indicated that, while the personality dimensions affected performance, there was no interaction between the personality dimensions and ambiguity

Si and Mn Abundances in Damped Lya Systems with Low Dust Content

We have measured the abundances of Zn, Si, Mn, Cr, Fe, and Ni in three damped Lyman alpha systems at redshifts z < 1 from high resolution echelle spectra of QSOs recorded with the Keck I telescope. In all three cases the abundances of Cr, Fe, and Ni relative to Zn indicate low levels of dust depletions. We propose that when the proportion of refractory elements locked up in dust grains is less than about 50 percent, it is plausible to assume an approximately uniform level of depletion for all grain constituents and, by applying a small dust correction, recover the intrisic abundances of Si and Mn. We use this approach on a small sample of damped systems for which it is appropriate, with the aim of comparing the metallicity dependence of the ratios [Si/Fe] and [Mn/Fe] with analogous measurements in Milky Way stars. The main conclusion is that the relative abundances of both elements in distant galaxies are broadly in line with expectations based on Galactic data. Si displays a mild enhancement at low metallicities, as expected for an alpha-capture element, but there are also examples of near-solar [Si/Fe] at [Fe/H] < -1. The underabundance of Mn at low metallicities is possibly even more pronounced than that in metal-poor stars, and no absorption system has yet been found where [Mn/Fe] is solar. The heterogeneous chemical properties of damped Lyman alpha systems, evident even from this limited set of measurements, provide further support for the conclusion from imaging studies that a varied population of galaxies gives rise to this class of QSO absorbers.Comment: 29 pages, LaTex, 7 Postscript Figures. Accepted for Publication in the Astrophysical Journa

Light-Induced TripletTriplet Electron Resonance Spectroscopy

We present a new technique, light-induced triplet-triplet electron resonance spectroscopy (LITTER), which measures the dipolar interaction between two photoexcited triplet states, enabling both the distance and angular distributions between the two triplet moieties to be determined on a nanometer scale. This is demonstrated for a model bis-porphyrin peptide that renders dipolar traces with strong orientation selection effects. Using simulations and density functional theory calculations, we extract distance distributions and relative orientations of the porphyrin moieties, allowing the dominant conformation of the peptide in a frozen solution to be identified. LITTER removes the requirement of current light-induced electron spin resonance pulse dipolar spectroscopy techniques to have a permanent paramagnetic moiety, becoming more suitable for in-cell applications and facilitating access to distance determination in unmodified macromolecular systems containing photoexcitable moieties. LITTER also has the potential to enable direct comparison with Förster resonance energy transfer and combination with microscopy inside cells

Hexanuclear Ln6L6 Complex Formation by using an Unsymmetric Ligand

Multinuclear, self‐assembled lanthanide complexes present clear opportunities as sensors and imaging agents. Despite the widely acknowledged potential of this class of supramolecule, synthetic and characterization challenges continue to limit systematic studies into their self‐assembly restricting the number and variety of lanthanide architectures reported relative to their transition metal counterparts. Here we present the first study evaluating the effect of ligand backbone symmetry on multinuclear lanthanide complex self‐assembly. Replacement of a symmetric ethylene linker with an unsymmetric amide at the centre of a homoditopic ligand governs formation of an unusual Ln6L6 complex with coordinatively unsaturated metal centres. The choice of triflate as a counterion, and the effect of ionic radii are shown to be critical for formation of the Ln6L6 complex. The atypical Ln6L6 architecture is characterized using a combination of mass spectrometry, luminescence, DOSY NMR and EPR spectroscopy measurements. Luminescence experiments support clear differences between comparable Eu6L6 and Eu2L3 complexes, with relatively short luminescent lifetimes and low quantum yields observed for the Eu6L6 structure indicative of non‐radiative decay processes. Synthesis of the Gd6L6analogue allows three distinct Gd···Gd distance measurements to be extracted using homo‐RIDME EPR experiments

Chelate-free metal ion binding and heat-induced radiolabeling of iron oxide nanoparticles† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4sc02778g Click here for additional data file.

A novel reaction for chelate-free, heat-induced metal ion binding and radiolabeling of ultra-small paramagnetic iron oxide nanoparticles (USPIOs) has been established. Radiochemical and non-radioactive labeling studies demonstrated that the reaction has a wide chemical scope and is applicable to p-, d- and f-block metal ions with varying ionic sizes and formal oxidation states from 2+ to 4+. Radiolabeling studies found that 89Zr–Feraheme (89Zr–FH or 89Zr–ferumoxytol) can be isolated in 93 ± 3% radiochemical yield (RCY) and >98% radiochemical purity using size-exclusion chromatography. 89Zr–FH was found to be thermodynamically and kinetically stable in vitro using a series of ligand challenge and plasma stability tests, and in vivo using PET/CT imaging and biodistribution studies in mice. Remarkably, ICP-MS and radiochemistry experiments showed that the same reaction conditions used to produce 89Zr–FH can be employed with different radionuclides to yield 64Cu–FH (66 ± 6% RCY) and 111In–FH (91 ± 2% RCY). Electron magnetic resonance studies support a mechanism of binding involving metal ion association with the surface of the magnetite crystal core. Collectively, these data suggest that chelate-free labeling methods can be employed to facilitate clinical translation of a new class of multimodality PET/MRI radiotracers derived from metal-based nanoparticles. Further, this discovery is likely to have broader implications in drug delivery, metal separation science, ecotoxicology of nanoparticles and beyond

Development and internal validation of the multivariable CIPHER (Collaborative Integrated Pregnancy High-dependency Estimate of Risk) clinical risk prediction model

Background: Intensive care unit (ICU) outcome prediction models, such as Acute Physiology And Chronic Health Evaluation (APACHE), were designed in general critical care populations and their use in obstetric populations is contentious. The aim of the CIPHER (Collaborative Integrated Pregnancy High-dependency Estimate of Risk) study was to develop and internally validate a multivariable prognostic model calibrated specifically for pregnant or recently delivered women admitted for critical care.Methods: A retrospective observational cohort was created for this study from 13 tertiary facilities across five high-income and six low- or middle-income countries. Women admitted to an ICU for more than 24 h during pregnancy or less than 6 weeks post-partum from 2000 to 2012 were included in the cohort. A composite primary outcome was defined as maternal death or need for organ support for more than 7 days or acute life-saving intervention. Model development involved selection of candidate predictor variables based on prior evidence of effect, availability across study sites, and use of LASSO (Least Absolute Shrinkage and Selection Operator) model building after multiple imputation using chained equations to address missing data for variable selection. The final model was estimated using multivariable logistic regression. Internal validation was completed using bootstrapping to correct for optimism in model performance measures of discrimination and calibration.Results: Overall, 127 out of 769 (16.5%) women experienced an adverse outcome. Predictors included in the final CIPHER model were maternal age, surgery in the preceding 24 h, systolic blood pressure, Glasgow Coma Scale score, serum sodium, serum potassium, activated partial thromboplastin time, arterial blood gas (ABG) pH, serum creatinine, and serum bilirubin. After internal validation, the model maintained excellent discrimination (area under the curve of the receiver operating characteristic (AUROC) 0.82, 95% confidence interval (CI) 0.81 to 0.84) and good calibration (slope of 0.92, 95% CI 0.91 to 0.92 and intercept of −0.11, 95% CI −0.13 to −0.08).Conclusions: The CIPHER model has the potential to be a pragmatic risk prediction tool. CIPHER can identify critically ill pregnant women at highest risk for adverse outcomes, inform counseling of patients about risk, and facilitate bench-marking of outcomes between centers by adjusting for baseline risk