Estimation of mass thickness response of embedded aggregated silica nanospheres from high angle annular dark-field scanning transmission electron micrographs

In this study we investigate the functional behavior of the intensity in high-angle annular dark field (HAADF) scanning transmission electron micrograph (STEM) images. The model material is a silica particle (20 nm) gel at 5 wt%. By assuming that the intensity response is monotonically increasing with increasing mass thickness of silica, an estimate of the functional form is calculated using a maximum likelihood approach. We conclude that a linear functional form of the intensity provides a fair estimate but that a power function is significantly better for estimating the amount of silica in the z-direction. The work adds to the development of quantifying material properties from electron micrographs, especially in the field of tomography methods and three-dimensional quantitative structural characterization from a STEM micrograph. It also provides means for direct three-dimensional quantitative structural characterization from a STEM micrograph

Multi-Scale Characterization of Lyotropic Liquid Crystals Using 2H and Diffusion MRI with Spatial Resolution in Three Dimensions

The ability of lyotropic liquid crystals to form intricate structures on a range of length scales can be utilized for the synthesis of structurally complex inorganic materials, as well as in devices for controlled drug delivery. Here we employ magnetic resonance imaging (MRI) for non-invasive characterization of nano-, micro-, and millimeter scale structures in liquid crystals. The structure is mirrored in the translational and rotational motion of the water, which we assess by measuring spatially resolved self-diffusion tensors and spectra. Our approach differs from previous works in that the MRI parameters are mapped with spatial resolution in all three dimensions, thus allowing for detailed studies of liquid crystals with complex millimeter-scale morphologies that are stable on the measurement time-scale of 10 hours. The data conveys information on the nanometer-scale structure of the liquid crystalline phase, while the combination of diffusion and data permits an estimate of the orientational distribution of micrometer-scale anisotropic domains. We study lamellar phases consisting of the nonionic surfactant C10E3 in O, and follow their structural equilibration after a temperature jump and the cessation of shear. Our experimental approach may be useful for detailed characterization of liquid crystalline materials with structures on multiple length scales, as well as for studying the mechanisms of phase transitions

Electroactive Polyhydroquinone Coatings for Marine Fouling Prevention—A Rejected Dynamic pH Hypothesis and a Deceiving Artifact in Electrochemical Antifouling Testing

Nanometer-thin coatings of polyhydroquinone (PHQ), which release and absorb protons upon oxidation and reduction, respectively, were tested for electrochemically induced anti-biofouling activity under the hypothesis that a dynamic pH environment would discourage fouling. Antifouling tests in artificial seawater using the marine, biofilm-forming bacterium Vibrio alginolyticus proved the coatings to be ineffective in fouling prevention but revealed a deceiving artifact from the reactive species generated at the counter electrode (CE), even for electrochemical bias potentials as low as |400| mV versus Ag|AgCl. These findings provide valuable information on the preparation of nanothin PHQ coatings and their electrochemical behavior in artificial seawater. The results further demonstrate that it is critical to isolate the CE in electrochemical anti-biofouling testing

Copper removal from acid mine drainage-polluted water using glutaraldehyde-polyethyleneimine modified diatomaceous earth particles

Mine waters and tailings generated from mining and mineral processing activities often have detrimental impact on the local environment. One example is acid mine drainage, in which sulphides in the mining waste react with water and oxygen to produce an acidic environment that subsequently dissolves host rock minerals from the waste containing toxic metals and trace elements. Copper is one such metal of significance, as it is mined at large volumes in sulphide containing ores. It has strong biocidal activity that greatly affects ecosystems. We have previously reported that glutaraldehyde (GA)-crosslinked polyethyleneimine (PEI) has strong affinity and selectivity for copper and that diatomaceous earth (DE) particles can be modified with the material to form a copper-extraction resin. In this study, the copper uptake of GA-PEI-DE particles was investigated from synthetic and real acid mine drainage samples under different pHs and their copper removal performance was compared with that of selected commercial resins. The results revealed that copper could effectively and preferentially bind to the material at pH 4, and that the copper could be completely eluted by lowering of the pH. In addition, effective copper uptake and elution was demonstrated using real legacy acid mine drainage water from Mount Lyell in Tasmania

Scaling exponent and dispersity of polymers in solution by diffusion NMR.

Molecular mass distribution measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) spectroscopy currently require prior knowledge of scaling parameters to convert from polymer self-diffusion coefficient to molecular mass. Reversing the problem, we utilize the scaling relation as prior knowledge to uncover the scaling exponent from within the PGSE data. Thus, the scaling exponent-a measure of polymer conformation and solvent quality-and the dispersity (Mw/Mn) are obtainable from one simple PGSE experiment. The method utilizes constraints and parametric distribution models in a two-step fitting routine involving first the mass-weighted signal and second the number-weighted signal. The method is developed using lognormal and gamma distribution models and tested on experimental PGSE attenuation of the terminal methylene signal and on the sum of all methylene signals of polyethylene glycol in D2O. Scaling exponent and dispersity estimates agree with known values in the majority of instances, leading to the potential application of the method to polymers for which characterization is not possible with alternative techniques

Polyethyleneimine for copper absorption: kinetics, selectivity and efficiency in artificial seawater

Published on 29 May 2014.Polyethyleneimine (PEI) is known to bind copper ions effectively and selectively. However, this is the first report on PEI-based materials for copper scavenging from ultra-low concentrations in seawater matrixes. The findings are relevant for water purification and sensing applications as well as extraction of copper from oceans.Johan B. Lindén, Mikael Larsson, Bryan R. Coad, William M. Skinner and Magnus Nydé

Unhindered copper uptake by glutaraldehyde-polyethyleneimine coatings in an artificial seawater model system with adsorbed swollen polysaccharides and competing ligand EDTA

Shortly after a surface is submerged in the sea, a conditioning film is generally formed by adsorption of organic molecules, such as polysaccharides. This could affect transport of molecules and ions between the seawater and the surface. An artificial seawater model system was developed to understand how adsorbed polysaccharides impact copper binding by glutaraldehyde-crosslinked polyethyleneimine coatings. Coating performance was also determined when competed against copper-chelating EDTA. Polysaccharide adsorption and copper binding and distribution were investigated using advanced analytical techniques, including depth-resolved time-of-flight secondary ion mass spectroscopy, grazing incidence X-ray absorption near-edge spectroscopy, quartz crystal microbalance with dissipation monitoring and X-ray photoelectron spectroscopy. In artificial seawater, the polysaccharides adsorbed in a swollen state that copper readily penetrated and the glutaraldehyde-polyethyleneimine coatings outcompeted EDTA for copper binding. Furthermore, the depth distribution of copper species was determined with nanometre precision. The results are highly relevant for copper-binding and copper-releasing materials in seawater

Behavioural difficulties that co-occur with specific word reading difficulties: A UK population-based cohort study

Open access articleThis is the peer reviewed version of the following article: Russell, G., Ryder, D., Norwich, B., and Ford, T. (2015), Behavioural Difficulties That Co-occur With Specific Word Reading Difficulties: A UK Population- Based Cohort Study. Dyslexia, 21, 123–141, which has been published in final form at 10.1002/dys.1496This study aimed to examine the association between specific word reading difficulties (SWRD) identified at age 7-years using a discrepancy approach and subsequent dimensional measures of behavioural difficulties reported by teachers and parents at age 11-years. Behavioural problems were assessed using the Strengths and Difficulties Questionnaire. Secondary analysis of a UK representative population-based sample of children (n-=-12-631) was conducted using linear regression models. There were 284 children (2.2%) identified with SWRD at age 7-years. Children with SWRD had significantly higher scores on all measures of behavioural difficulties in unadjusted analysis. SWRD was associated with elevated behavioural difficulties at age 11-years according to parent report, and with greater emotional problems, hyperactivity and conduct issues according to teachers, even after having controlled for baseline difficulties. These results were replicated for children with low reading attainment, but no cognitive ability discrepancy. Categories of special educational need into which children with SWRD were classed at school were varied. Given high rates of co-occurring behavioural difficulties, assessment that identifies each individual child's specific functional, rather than categorical, difficulties is likely to be the most effective way of providing classroom support.Economic & Social Research Council (ESRC

Psychiatric and psychosocial problems in adults with normal-intelligence autism spectrum disorders

<p>Abstract</p> <p>Background</p> <p>Individuals with autism spectrum disorders (ASDs) often display symptoms from other diagnostic categories. Studies of clinical and psychosocial outcome in adult patients with ASDs without concomitant intellectual disability are few. The objective of this paper is to describe the clinical psychiatric presentation and important outcome measures of a large group of normal-intelligence adult patients with ASDs.</p> <p>Methods</p> <p>Autistic symptomatology according to the DSM-IV-criteria and the Gillberg & Gillberg research criteria, patterns of comorbid psychopathology and psychosocial outcome were assessed in 122 consecutively referred adults with normal intelligence ASDs. The subjects consisted of 5 patients with autistic disorder (AD), 67 with Asperger's disorder (AS) and 50 with pervasive developmental disorder not otherwise specified (PDD NOS). This study group consists of subjects pooled from two studies with highly similar protocols, all seen on an outpatient basis by one of three clinicians.</p> <p>Results</p> <p>Core autistic symptoms were highly prevalent in all ASD subgroups. Though AD subjects had the most pervasive problems, restrictions in non-verbal communication were common across all three subgroups and, contrary to current DSM criteria, so were verbal communication deficits. Lifetime psychiatric axis I comorbidity was very common, most notably mood and anxiety disorders, but also ADHD and psychotic disorders. The frequency of these diagnoses did not differ between the ASD subgroups or between males and females. Antisocial personality disorder and substance abuse were more common in the PDD NOS group. Of all subjects, few led an independent life and very few had ever had a long-term relationship. Female subjects more often reported having been bullied at school than male subjects.</p> <p>Conclusion</p> <p>ASDs are clinical syndromes characterized by impaired social interaction and non-verbal communication in adulthood as well as in childhood. They also carry a high risk for co-existing mental health problems from a broad spectrum of disorders and for unfavourable psychosocial life circumstances. For the next revision of DSM, our findings especially stress the importance of careful examination of the exclusion criterion for adult patients with ASDs.</p