Mechanisms that limit the thermotropic alignment of a liquid crystal semiconducting polymer on a rubbed polyimide film were studied using three different molecular weights of ...poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), one of a large class of polyfluorene polymers currently being investigated for use in highly polarized light-emitting diodes and high-performance polymer-based transistors. The molecular weight was found to influence the melting temperature of the polymer, the speed at which the polymer aligns to a rubbed surface, and the ultimate molecular alignment that can be achieved. The alignment of F8BT with the highest molecular weight was severely limited by the viscosity of the polymer, while the films with low and intermediate molecular weights reached a maximum alignment in reasonable processing times. The maximum saturated dichroic ratio (D max) was consistently higher, the largest D max observed was over 29, in the lowest molecular weight films. Optical microscopy revealed that the lower dichroic ratio could be attributed to an inability of the domains in the higher molecular weight film to reorient to the templating direction; thus, the final film retains a multidomain structure. This has serious implications on the charge transport through these materials since any domain boundaries will adversely affect the charge carrier mobility. Therefore, despite the advantages that higher molecular weights could have on optoelectronic device performance, the long chain lengths will also limit macroscopic liquid crystalline alignment. For F8BT, the maximum molecular weight in which monodomain alignment is still achieved appears to be in the range 62 000−129 000.
Metallic nanoparticles embedded into the structure of metal oxides may play a role of catalytic substances. Such composites are mostly applied in oxidation reactions. The paper presents two ...one-step-methods for obtaining nanocomposites of gold embedded in the structure of iron oxide matrices (nanoAu/Fe
2
O
3
). Gold nanoparticles were formed in situ in the process of iron hydroxide dehydration. Thanks to the use of tannic acid it was possible to effectively reduce gold ions and stabilize the forming metal nanoparticles. The composites were prepared in the fields of microwave, ultraviolet radiation. The physicochemical properties of products were determined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray analysis and high-resolution transmission electron microscopy technique with EDS and elemental mapping mode. Also, the catalytic activity of the nanocomposites obtained was evaluated based on the process of methyl orange degradation. It was observed that products obtained according to the microwave radiation method are characterized by improved applying properties.
This paper introduces a new model that enables researchers to conduct protein folding simulations. A two-step
in silico process is used in the course of structural analysis of a set of fast-folding ...proteins. The model assumes an early stage (ES) that depends solely on the backbone conformation, as described by its geometrical properties—specifically, by the
V-angle between two sequential peptide bond planes (which determines the radius of curvature, also called R-radius, according to a second-degree polynomial form). The agreement between the structure under consideration and the assumed model is measured in terms of the magnitude of dispersion of both parameters with respect to idealized values. The second step, called late-stage folding (LS), is based on the “fuzzy oil drop” model, which involves an external hydrophobic force field described by a three-dimensional Gauss function. The degree of conformance between the structure under consideration and its idealized model is expressed quantitatively by means of the Kullback–Leibler entropy, which is a measure of disparity between the observed and expected hydrophobicity distributions. A set of proteins, representative of the fast-folding group – specifically, cold shock proteins – is shown to agree with the proposed model.
► Two-step process for protein folding process is presented using down-hill proteins. ► The accordance with assumed early and late-stage intermediate is presented. ► The early-stage intermediate is analyzed using backbone conformation. ► The late-stage intermediate is characterized by hydrophobic core structure. ► The accordance is measured using elements of information theory.
Abstract
Background
The use of electronic nicotine delivery systems (ENDS) is becoming increasingly prevalent. Yet, its association with risk of stroke is still uncertain and not well-established.
...Purpose
To synthesize more conclusive evidence about the association between ENDS use and risk of stroke through a systematic review and meta-analysis of available observational studies.
Methods
PubMed, Scopus, and Web of Science databases were searched from inception until February 20, 2023, to identify observational studies (either cross sectional, cohort, or case-control studies) that assessed the association of ENDS use with risk of stroke compared with non-users. Adjusted risk estimates of stroke form each relevant study were extracted and pooled as odds ratio (OR) with 95% confidence interval (CI) under the random-effects meta-analysis model. We also performed a leave-one-out sensitivity analysis to evaluate the robustness of the combined result. The I2 statistic was used to quantify heterogeneity.
Results
Six studies (four cross-sectional and two prospective cohort studies) with a total of 822,162 participants (ENDS users=38,539 and non-users=783,623) matched our criteria and were included in this meta-analysis. The analysis revealed that ENDS use was associated with a statistically significant increased risk of stroke (OR: 1.48 95% CI: 1.07 to 2.05; I2: 82%; Figure 1A) compared with non-users. This result was sensitive (i.e., became statistically insignificant) to the removal of one study by Bricknell and co-authors l (OR: 1.44 95% CI: 0.96 to 2.18; I2: 85%; Figure 1B).
Conclusion
The usage of ENDS appears to be associated with a greater risk of stroke when compared with a lack of use. Further well-designed longitudinal investigations are needed to validate these findings and investigate the potential mechanisms implicated with this association.
Figure 1: (A) results of meta-analysis of the included studies that assessed the association of ENDS use with risk of stroke (B) results of the leave-one-out sensitivity analysis.
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