Chemical Composition of Polymer Surfaces Imaged by Atomic ForceMicroscopy and Complementary Approaches

In this article we review the recent developments in the field of high resolution lateral mapping of the surface chemical composition of polymers by atomic force microscopy (AFM) and other complementary imaging techniques. The different AFM approaches toward nanometer scale mapping with chemical sensitivity based on chemical force microscopy (CFM) are discussed as a means to unravel, for instance, the lateral distribution of surface chemistry, the stability of various types of functional groups in various environments, or the interactions with controlled functional groups at the tip surface. The applicability and current limitations of CFM, which allows one to image chemical functional group distributions with a resolution in principle down to the 10–20 nm scale, are critically discussed. In addition, complementary imaging techniques are briefly reviewed and compared to the AFM-based techniques. The complementary approaches comprise various spectroscopies (infrared and Raman), secondary ion mass spectrometry (SIMS), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), X-ray photoelectron spectroscopy (XPS or ESCA), and near-field optical techniques used for imaging

Expectations, visions and sense of empowerment: in the face of a vocational rehabilitation process for people with psychiatric disabilities

The aim of this study is to reveal the meaning some people with psychiatric disabilities assigned to important experiences related to long periods of participation restrictions owing to unemployment and sick leave. The data comprise open-ended interviews with eight informants. A hermeneutic approach together with a comparative analysis was used to analyze the data. The results showed six types of mechanisms important for the outcome of the rehabilitation process: support, understanding, time, control, self-image and vision of the future. Our results indicate that environmental factors such as experience of support and understanding of professionals and time-efficacy seemed to have a great effect on the individuals' attitudes concerning the activities and measures they expected to carry out during their coming rehabilitation. These experiences seemed to affect their belief in their own abilities, their sense of control, and their belief in successful performance. Theories about empowerment closely related to social emotions like pride and shame are also discussed in an attempt to deepen the understanding of the studied phenomena

Lamellae-controlled electrical properties of polyethylene-morphology, oxidation and effects of antioxidant on the DC conductivity

Destruction of the spherulite structure in low-density polyethylene (LDPE) is shown to result in a more insulating material at low temperatures, while the reverse effect is observed at high temperatures. On average, the change in morphology reduced the conductivity by a factor of 4, but this morphology-related decrease in conductivity was relatively small compared with the conductivity drop of more than 2 decades that was observed after slight oxidation of the LDPE (at 25 \ub0C and 30 kV mm-1). The conductivity of LDPE was measured at different temperatures (25-60 \ub0C) and at different electrical field strengths (3.3-30 kV mm-1) for multiple samples with a total crystalline content of 51 wt%. The transformation from a 5 μm coherent structure of spherulites in the LDPE to an evenly dispersed random lamellar phase (with retained crystallinity) was achieved by extrusion melt processing. The addition of 50 ppm commercial phenolic antioxidant to the LDPE matrix (e.g. for the long-term use of polyethylene in high voltage direct current (HVDC) cables) gave a conductivity ca. 3 times higher than that of the same material without antioxidants at 60 \ub0C (the operating temperature for the cables). For larger amounts of antioxidant up to 1000 ppm, the DC conductivity remained stable at ca. 1 7 10-14 S m-1. Finite element modeling (FEM) simulations were carried out to model the phenomena observed, and the results suggested that the higher conductivity of the spherulite-containing LDPE stems from the displacement and increased presence of polymeric irregularities (formed during crystallization) in the border regions of the spherulite structures

Tuneable conductivity at extreme electric fields in ZnO tetrapod-silicone composites for high-voltage power cable insulation

Resistive Field Grading Materials (RFGM) are used in critical regions in the electrical insulation system of high-voltage direct-current cable systems. Here, we describe a novel type of RFGM, based on a percolated network of zinc oxide (ZnO) tetrapods in a rubber matrix. The electrical conductivity of the composite increases by a factor of 108 for electric fields > 1\ua0kV\ua0mm-1, as a result of the highly anisotropic shape of the tetrapods and their significant bandgap (3.37\ua0eV). We demonstrate that charge transport at fields < 1\ua0kV\ua0mm-1 is dominated by thermally activated hopping of charge carriers across spatially, as well as energetically, localized states at the ZnO-polymer interface. At higher electric fields (> 1\ua0kV\ua0mm-1) band transport in the semiconductive tetrapods triggers a large increase in conductivity. These geometrically enhanced ZnO semiconductors outperform standard additives such as SiC particles and ZnO micro varistors, providing a new class of additives to achieve variable conductivity in high-voltage cable system applications

Spiropyran modified micro-fluidic chip channels as photonically controlled self-indicating system for metal ion accumulation and release

In this paper, we show how through integrating the beneficial characteristics of micro-fluidic devices and spiropyrans dyes, a simple and very innovative chip configured as an on-line photonically controlled self-indicating system for metal ion accumulation and release can be realised. The micro-fluidic device consists of five independent 94 μm depth, 150 μm width channels fabricated in polydimethylsiloxane. The spiropyran 1’-(3-carboxypropyl)-3,3’-dimethyl-6-nitrospiro-1-benzopyran-2,2’-indoline is immobilised by physical adsorption into a polydimethylsiloxane matrix and covalently on the ozone plasma activated polydimehylsiloxane micro-channel walls. When the colourless, inactive, spiropyran coating absorbs UV light it switches to the highly coloured merocyanine form, which also has an active binding site for certain metal ions. Therefore metal ion uptake can be triggered using UV light and subsequently reversed on demand by shining white light on the coloured complex, which regenerates the inactive spiropyran form, and releases the metal ion. When stock solutions of several metal ions (Ca2+, Zn2+, Hg2+, Cu2+, Co2+) are pumped independently through the five channels, different optical responses were observed for each metal, and the platform can therefore be regarded as a micro-structured device for online self-indicating metal ion complexation, accumulation and release

The Mechanical Properties of Epoxy Composites Filled with Rubbery Copolymer Grafted SiO\u3csub\u3e2\u3c/sub\u3e

This study demonstrated a method for toughening a highly crosslinked anhydride cured DGEBA epoxy using rubbery block copolymer grafted SiO2 nanoparticles. The particles were synthesized by a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. The inner rubbery block poly(n-hexyl methacrylate) (PHMA) had a glass transition temperature below room temperature. The outer block poly(glycidyl methacrylate) (PGMA) was matrix compatible. A rubbery interlayer thickness of 100% and 200% of the particle core radius was achieved by grafting a 20 kg/mol and a 40 kg/mol PHMA at a graft density of 0.7 chains/nm2 from the SiO2 surface. The 20 kg/mol rubbery interlayer transferred load more efficiently to the SiO2 cores than the 40 kg/mol rubbery interlayer and maintained the epoxy modulus up to a loading of 10 vol% of the rubbery interlayer. Both systems enabled cavitation or plastic dilatation. Improvement of the strain-to-break and the tensile toughness was found in both systems. We hypothesize that plastic void growth in the matrix is the primary mechanism causing the improvement of the ductility

Effectiveness of multimodal treatment for young people with body dysmorphic disorder in two specialist clinics

Body dysmorphic disorder (BDD) typically originates in adolescence and is associated with considerable adversity. Evidence-based treatments exist but research on clinical outcomes in naturalistic settings is extremely scarce. We evaluated the short- and long-term outcomes of a large cohort of adolescents with BDD receiving specialist multimodal treatment and examined predictors of symptom improvement. We followed 140 young people (age range 10-18) with a diagnosis of BDD treated at two national and specialist outpatient clinics in Stockholm, Sweden (n=96) and London, England (n=44), between January 2015 and April 2021. Participants received multimodal treatment consisting of cognitive behaviour therapy and, in 72% of cases, medication (primarily selective serotonin reuptake inhibitors). Data were collected at baseline, post-treatment, and 3, 6, and 12 months after treatment. The primary outcome measure was the clinician-rated Yale-Brown Obsessive-Compulsive Scale Modified for BDD, Adolescent version (BDD-YBOCS-A). Secondary outcomes included self-reported measures of BDD symptoms, depressive symptoms, and global functioning. Mixed-effects regression models showed that BDD-YBOCS-A scores decreased significantly from baseline to post-treatment (coefficient [95% confidence interval]=-16.33 [-17.90 to -14.76], p<0.001; within-group effect size (Cohen’s d)=2.08 (95% confidence interval, 1.81 to 2.35). At the end of the treatment, 79% of the participants were classified as responders and 59% as full or partial remitters. BDD symptoms continued to improve throughout the follow-up. Improvement was also seen on all secondary outcome measures. Linear regression models identified baseline BDD symptom severity as a predictor of treatment outcome at post-treatment, but no consistent predictors were found at the 12-month follow-up. To conclude, multimodal treatment for adolescent BDD is effective in both the short- and long-term when provided flexibly within a specialist setting. Considering the high personal and societal costs of BDD, specialist care should be made more widely available

Functional single-cell analysis of T-cell activation by supported lipid bilayer-tethered ligands on arrays of nanowells

Supported lipid bilayers are an important biomolecular tool for characterizing immunological synapses. Immobilized bilayers presenting tethered ligands on planar substrates have yielded both spatio-temporal and structural insights into how T cell receptors (TCRs) reorganize during the initial formation of synapses upon recognition of peptide antigens bound to major histocompatibility complex (MHC) molecules. The prototypical configuration of these assays, however, limits the extent to which the kinetics and structure of the supramolecular activation clusters of the synapse (that occur in seconds or minutes) can be related to subsequent complex cellular responses, such as cytokine secretion and proliferation, occurring over hours to days. Here we describe a new method that allows correlative measures of both attributes with single-cell resolution by using immobilized lipid bilayers and tethered ligands on the surface of dense arrays of subnanoliter wells. This modification allows each nanowell to function as an artificial antigen-presenting cell (APC), and the synapses formed upon contact can be imaged by fluorescence microscopy. We show that the lipid bilayers remain stable and mobile on the surface of the PDMS, and that modifying the ligands tethered to the bilayer alters the structure of the resulting synapses in expected ways. Finally, we demonstrate that this approach allows the subsequent characterization of secreted cytokines from the activated human T cell clones by microengraving in both antigen- and pan-specific manners. This new technique should allow detailed investigations on how biophysical and structural aspects of the synapse influence the activation of individual T cells and their complex functional responses.National Institute of Allergy and Infectious Diseases (U.S.) (5P01AI045757)National Cancer Institute (U.S.) (Cancer Center Support (Core) Grant P30-CA14051