An assessment of the causes of the errors in the 2015 UK General Election opinion polls

The opinion polls undertaken prior to the 2015 UK General Election under-estimated the Conservative lead over Labour by an average of 7 percentage points. This collective failure led politicians and commentators to question the validity and utility of political polling and raised concerns regarding a broader public loss of confidence in survey research. In this paper, we assess the likely causes of the 2015 polling errors. We begin by setting out a formal account of the statistical methodology and assumptions required for valid estimation of party vote shares using quota sampling. We then describe the current approach of polling organisations for estimating sampling variability and suggest a new method based on bootstrap re-sampling. Next, we use poll micro-data to assess the plausibility of different explanations of the polling errors. Our conclusion is that the primary cause of the polling errors in 2015 was unrepresentative sampling

Table_1_Publishing in English or Chinese: a qualitative analysis of Chinese researchers’ academic language choice.DOCX

Non-native language scholars often struggle to choose between English and their native language in scholarly publishing. This study aims to identify the mechanism by which journal attributes influence language choice by investigating the perspectives of 18 Chinese scholars through semi-structured interviews. Drawing on grounded theory, this study develops a model for how journal attributes influence researchers’ language preferences. We find that journal attributes influence researchers’ perceived value which, in turn, affects their particular language choice, with contextual factors playing a moderating role. By examining the motivations underlying Chinese scholars’ language choice, this study provides a critical understanding of the factors shaping their decision-making processes. These findings have significant implications for Chinese scholars, policymakers, and journal operators, shedding light on the issue of discrimination in academic publishing. Addressing these concerns is crucial for fostering a fair and inclusive academic environment.</p

Effect of Chain Conformation on the Single-Molecule Melting Force in Polymer Single Crystals: Steered Molecular Dynamics Simulations Study

Understanding the relationship between polymer chain conformation as well as the chain composition within the single crystal and the mechanical properties of the corresponding single polymer chain will facilitate the rational design of high performance polymer materials. Here three model systems of polymer single crystals, namely poly­(ethylene oxide) (PEO), polyethylene (PE), and nylon-66 (PA66) have been chosen to study the effects of chain conformation, helical (PEO) versus planar zigzag conformation (PE, PA66), and chain composition (PE versus PA66) on the mechanical properties of a single polymer chain. To do that, steered molecular dynamics simulations were performed on those polymer single crystals by pulling individual polymer chains out of the crystals. Our results show that the patterns of force–extension curve as well as the chain moving mode are closely related to the conformation of the polymer chain in the single crystal. In addition, hydrogen bonds can enhance greatly the force required to stretch the polymer chain out of the single crystal. The dynamic breaking and reformation of multivalent hydrogen bonds have been observed for the first time in PA66 at the single molecule level

Oxidative CO₂ Reforming of Methane in La_0.6Sr_0.4Co_0.8Ga_0.2O_3‑δ (LSCG) Hollow Fiber Membrane Reactor

CO₂ utilization in catalytic membrane reactors for syngas production is an environmentally benign solution to counter the escalating global CO₂ concerns. In this study, integration of a La_0.6Sr_0.4Co_0.8Ga_0.2O_3‑δ (LSCG) hollow fiber membrane reactor with Ni/LaAlO₃–Al₂O₃ catalyst for the oxidative CO₂ reforming of methane (OCRM) reaction was successfully tested for 160 h of reaction. High CH₄ and CO₂ conversions of ca. 94% and 73% were obtained with O₂ flux ca. 1 mL·min^–1·cm^–2 at 725 °C for the 160-h stability test. Surface temperature programmed desorption studies of the membrane were conducted with H₂, CO, and CO₂ as probe gases to facilitate understanding on the effect of H₂ and CO product gases as well as CO₂ reactant gases on the membrane surface. Scanning electron microscopy–energy dispersive X-ray (SEM-EDX), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) analysis of the postreacted membrane after 160-h stability tests suggests Sr-enriched phases with the presence of adsorbed carbonate and hydrogenated carbon. This shows the subsequent reactant spillover on the membrane surface from the catalyst bed took place due to the reaction occurring on the catalyst. However, XRD analysis of the bulk structure does not show any phase impurities, thus confirming the structural integrity of the LSCG hollow fiber membrane

Effect of Chain Conformation on the Single-Molecule Melting Force in Polymer Single Crystals: Steered Molecular Dynamics Simulations Study

Understanding the relationship between polymer chain conformation as well as the chain composition within the single crystal and the mechanical properties of the corresponding single polymer chain will facilitate the rational design of high performance polymer materials. Here three model systems of polymer single crystals, namely poly­(ethylene oxide) (PEO), polyethylene (PE), and nylon-66 (PA66) have been chosen to study the effects of chain conformation, helical (PEO) versus planar zigzag conformation (PE, PA66), and chain composition (PE versus PA66) on the mechanical properties of a single polymer chain. To do that, steered molecular dynamics simulations were performed on those polymer single crystals by pulling individual polymer chains out of the crystals. Our results show that the patterns of force–extension curve as well as the chain moving mode are closely related to the conformation of the polymer chain in the single crystal. In addition, hydrogen bonds can enhance greatly the force required to stretch the polymer chain out of the single crystal. The dynamic breaking and reformation of multivalent hydrogen bonds have been observed for the first time in PA66 at the single molecule level

Nanostructures, Linear Rheological Responses, and Tunable Mechanical Properties of Microphase-Separated Cellulose-<i>graft</i>-Diblock Bottlebrush Copolymer Elastomers

A series of cellulose-graft-diblock bottlebrush copolymer elastomers (cellulose-graft-poly(n-butyl acrylate)-block-poly(methyl methacrylate) (Cell-g-PBA-b-PMMA)) with short side chains were synthesized via successive atom transfer radical polymerization (ATRP) to study the influence of varying compositions and lengths of the graft diblock side chains on microphase morphologies and properties. The microphase-separated morphologies from misaligned spheres to cylinders were observed by atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) measurements. These bottlebrush copolymer elastomers possessed thermal stability and enhanced mechanical properties because the PMMA outer block could self-assemble into hard microdomains, which served as physical cross-links. The viscoelastic responses of these bottlebrush copolymers within the linear viscoelastic (LVE) regime were carried out by the oscillatory shear rheology. The time–temperature superposition (tTs) principle was applied to construct the master curves of the dynamic moduli, and the sequential relaxation of dense bottlebrush copolymers with different PMMA hard outer block lengths was analyzed. The rheological behaviors in this work could be utilized to build up the connection of microstructures and properties for the application of these bottlebrush copolymers as high-performance thermoplastic elastomers

Synthesis of Structure-Controlled Polyborosiloxanes and Investigation on Their Viscoelastic Response to Molecular Mass of Polydimethylsiloxane Triggered by Both Chemical and Physical Interactions

A series of polyborosiloxanes (PBSs) was synthesized by mixing hydroxy-terminated polydimethylsiloxanes (PDMS) and boric acid (BA) in toluene at 120 °C. The molecular masses of selected PDMS precursors were in a wide range, covering from below up to far above the critical entanglement molecular mass of PDMS. The reaction kinetics was followed by using Fourier transform infrared (FTIR) spectroscopy. Unreacted BA was removed from raw PBSs after the reactions. The influence of molecular mass of PDMS precursors on the rheological property of PBSs was explored by dynamic oscillatory frequency sweeps. The results showed that the plateau elastic moduli of PBSs were highly dependent on the molecular mass of PDMS precursors. The plateau elastic moduli of PBSs decreased at first and then increased with increasing molecular mass of PDMS precursors. PBS1 and PBS2 prepared from unentangled PDMS precursors showed sufficient fits by using the two-mode Maxwell model, whereas PBS3 to PBS6 prepared from highly entangled PDMS precursors showed obvious deviations from the two-mode Maxwell model. It could be concluded that the changing trend of plateau elastic modulus of PBSs versus molecular mass of PDMS precursors was determined by the number density of supramolecular interactions (Si–O:B weak bonding and hydrogen-bonding of the end groups Si–O–B­(OH)₂) and the number density of topological entanglements

Magnetoporation and Magnetolysis of Cancer Cells via Carbon Nanotubes Induced by Rotating Magnetic Fields

Weak magnetic fields (40 and 75 mT) were used either to enhance cell membrane poration (magnetoporation) or to ablate cultured human tumor cells (magnetolysis) by polymer-coated multiwalled carbon nanotubes, which form rotating bundles on exposure to magnetic fields. Findings of this study have potential clinical applications including enhanced tumor cell poration for targeted cancer chemotherapy and mechanical ablation of tumors

Speeding of Spherulitic Growth Rate at the Late Stage of Isothermal Crystallization Due to Interfacial Diffusion for Double-Layer Semicrystalline Polymer Films

In this study a unique phenomenon has been found for isothermal crystallization of double-layer semicrystalline polymer films. It is surprisingly found that there exists a speeding of poly­(l-lactic acid) (PLA) spherulitic growth rate for poly­(ethylene oxide)/poly­(l-lactic acid) (PEO/PLA) double-layer films at the late stage of isothermal crystallization, which does not exist for PLA/PEO blend films and neat PLA films. The mutual diffusion between PEO and PLA layers plays the key factor to bring out the observed speeding of spherulitic growth rate. This type of study provides an avenue for understanding the interplay between polymer crystallization and interfacial diffusion in multilayer polymer films, which is not available when employing the polymer blend films

Supertoughened Polylactide Binary Blend with High Heat Deflection Temperature Achieved by Thermal Annealing above the Glass Transition Temperature

Through thermal annealing above the glass transition temperature, a supertoughened binary blend with the highest notched Izod impact strength of 98 KJ/m² was achieved, which was about 52 times of that of neat polylactide (PLA; 1.9 KJ/m²). The binary blend was composed of biocompatible and biodegradable PLA and ethylene–acrylic ester–glycidyl methacrylate terpolymer (EGMA) elastomer at the composition of 80/20 PLA/EGMA. For one toughened binary blend with the notched Izod impact strength of 94 KJ/m², its tensile elongation at break was kept above 120%. Moreover, this supertoughened binary blend also displayed a much higher heat deflection temperature for application. Thermal annealing induced crystallization of the PLA matrix in the blend, and a linear correlation between the notched Izod impact strength and crystallinity was revealed. The possible toughening mechanism for the PLA/EGMA 80/20 blend with thermal annealing was analyzed from the viewpoint of negative pressure effects, as imposed on EGMA elastomeric particles during the quench process and thermal annealing thereafter. Decreases of the glass transition temperatures for the EGMA elastomeric particles in the blend were observed for both the quench and thermal annealing processes, which originated from asymmetric thermal shrinkages between the EGMA elastomeric phase and PLA matrix phase