Measuring the polymerization stress of self-adhesive resin composite cements by crack propagation.

OBJECTIVES: To test the polymerization stress of nine self-adhesive resin composite cements (G-CEM, iCEM, Bifix SE, Maxcem Elite, PANAVIA SA, SoloCem, SmartCem 2, SpeedCEM, RelyX Unicem 2) and one glass ionomer cement (control group; Ketac Cem). MATERIALS AND METHODS: The crack propagation of a feldspar ceramic (n = 130) was determined by measuring crack lengths that originated from Vickers indentations, prior to and after the application and polymerization of the self-adhesive resin cements. Results for crack propagation were converted to polymerization stress values, and statistical analysis was performed using one-way ANOVA followed by Scheffé post hoc test. RESULTS: SmartCem 2 presented higher stress values than iCEM, SoloCem, and Ketac Cem, while Ketac Cem showed lower values than Bifix SE, Maxcem Elite, SmartCem 2, SpeedCEM, and RelyX Unicem 2. CONCLUSIONS: Self-adhesive resin composite cements differ in their polymerization stress, which may affect the durability of the restoration. For restorations made from ceramics with lower flexural strength, such as feldspar ceramics, resin composite cement materials with less polymerization stress should be preferred. CLINICAL RELEVANCE: As a high polymerization shrinkage may increase crack propagation, the determination of the polymerization stress of self-adhesive resin composite cements employed for fixing all-ceramic restorations is an important factor.

On Demand Light-Degradable Polymers Based on 9,10-Dialkoxyanthracenes.

Light induced degradation of polymers has drawn increasing interest due to the need for externally controllable modulation of materials properties. However, the portfolio of polymers, that undergo precisely controllable degradation, is limited and typically requires UV light. A novel class of backbone-degradable polymers that undergo aerobic degradation in the presence of visible light, yet remain stable against broad-spectrum light under anaerobic conditions is reported. In this design, the polymer backbone is comprised of 9,10-dialkoxyanthracene units that are selectively cleaved by singlet oxygen in the presence of green light as confirmed by NMR and UV/vis spectroscopy. The resulting polymers have been processed by electrohydrodynamic (EHD) co-jetting into bicompartmental microfibers, where one hemisphere is selectively degraded on demand.

Total organic carbon quantification in soils and sediments: Performance test of a modified sample preparation method.

The total organic carbon (TOC) concentration of particulate samples is a key parameter to characterize soils and sediments. To demonstrate the applicability and reliability of a modified sample preparation method for the direct measurement of TOC contents in suspended particulate samples, we analyzed five certified reference materials (CRMs) with varying TOC concentrations using a Shimadzu TOC-L CPH analyzer. Measured values were calibrated with a multi-point curve that cover the full range of the expected TOC concentrations and the results were validated using statistical values and measures. The method validation reveals that the measurements are accurate and precise for CRMs from marine and soil contexts, but show a low accuracy for the CRM containing polycyclic aromatic hydrocarbons (PAHs). This demonstrates the applicability and reliability of the modified preparation method for direct TOC determination of suspended particulate samples. Therefore, it is relevant for a broader community, beyond geosciences, and for users employing devices of other manufacturers to analyze TOC in suspended particulate samples.•Modified preparation method uses reduced sample weights and yields accurate and precise results.•Cost-efficient and environmentally friendly alternative: reduces waste by saving acid and ultrapure water.•Avoids incomplete dissolution of dolomite by heating acidified samples.

Correction: Selective area growth of GaN nanowires and nanofins by molecular beam epitaxy on heteroepitaxial diamond (001) substrates.

[This corrects the article DOI: 10.1039/D1NA00221J.].

Selective area growth of GaN nanowires and nanofins by molecular beam epitaxy on heteroepitaxial diamond (001) substrates.

GaN-on-diamond is a promising route towards reliable high-power transistor devices with outstanding performances due to better heat management, replacing common GaN-on-SiC technologies. Nevertheless, the implementation of GaN-on-diamond remains challenging. In this work, the selective area growth of GaN nanostructures on cost-efficient, large-scale available heteroepitaxial diamond (001) substrates by means of plasma-assisted molecular beam epitaxy is investigated. Additionally, we discuss the influence of an AlN buffer on the morphology of the GaN nanostructures. The nanowires and nanofins are characterized by a very high selectivity and controllable dimensions. Low temperature photoluminescence measurements are used to evaluate their structural quality. The growth of two GaN crystal domains, which are in-plane rotated against each other by 30°, is observed. The favoring of a certain domain is determined by the off-cut direction of the diamond substrates. By X-ray diffraction we show that the GaN nanostructures grow perpendicular to the diamond surface on off-cut diamond (001) substrates, which is in contrast to the growth on diamond (111), where the nanostructures are aligned with the substrate lattice. Polarity-selective wet chemical etching and Kelvin probe force microscopy reveal that the GaN nanostructures grow solely in the Ga-polar direction. This is a major advantage compared to the growth on diamond (111) and enables the application of GaN nanostructures on cost-efficient diamond for high-power/high-frequency applications.

Stiffness Estimates for Composites with Elliptic Cylindrical Voids.

A two-step homogenization procedure is presented to investigate the stiffness of a unidirectional continuous fiber-reinforced composite material containing voids of different shapes and volume contents. Since the Mori-Tanaka scheme is limited to moderate volume contents of the inhomogeneity phase, fiber and matrix are homogenized with semi-empirical relations with use of the adjusted fiber volume content in a first step. In the second step, the Mori-Tanaka scheme is applied to obtain the homogenized stiffness tensor of a transversely isotropic material containing voids aligned with the fiber direction. The voids are modelled with infinite length, but an elliptic base characterized by the aspect ratio. The tensor components of the Eshelby tensor for this case are presented in closed form for a transversely isotropic material depending on the aspect ratio and matrix material properties. The scheme is solved directly for easy implementation and the use of fast calculations of the effective engineering constants of a composite material containing voids. Experimental results from literature for different void contents and shapes are compared to the predicted moduli with cylindrical voids. From the results it is further concluded that the aspect ratio of the void and the manufacturing process of the composite should be considered.

The furnace and the goat-A spatio-temporal model of the fuelwood requirement for iron metallurgy on Elba Island, 4th century BCE to 2nd century ce.

Scholars frequently cite fuel scarcity after deforestation as a reason for the abandonment of most of the Roman iron smelting sites on Elba Island (Tuscan Archipelago, Italy) in the 1st century bce. Whereas the archaeological record clearly indicates the decrease in smelting activities, evidence confirming the 'deforestation narrative' is ambiguous. Therefore, we employed a stochastic, spatio-temporal model of the wood required and consumed for iron smelting on Elba Island in order to assess the availability of fuelwood on the island. We used Monte Carlo simulations to cope with the limited knowledge available on the past conditions on Elba Island and the related uncertainties in the input parameters. The model includes both, wood required for the furnaces and to supply the workforce employed in smelting. Although subject to high uncertainties, the outcomes of our model clearly indicate that it is unlikely that all woodlands on the island were cleared in the 1st century bce. A lack of fuel seems only likely if a relatively ineffective production process is assumed. Therefore, we propose taking a closer look at other reasons for the abandonment of smelting sites, e.g. the occupation of new Roman provinces with important iron ore deposits; or a resource-saving strategy in Italia. Additionally, we propose to read the development of the 'deforestation narrative' originating from the 18th/19th century in its historical context.

Optimizing Organ Donation: Expert Opinion from Austria, Germany, Spain and the U.K.

BACKGROUND Organ donation-rates using deceased donors and organizational approaches to organ donation differ drastically between countries at a similar level of health care as measured by the Euro Health Consumer Index (EHCI). MATERIAL AND METHODS Expert opinions from intensive care nurses, physicians, transplant coordinators and transplant surgeons from Austria, Germany, Spain, and the U.K. were obtained in semi-structured interviews followed by qualitative content analysis. Results were reported back to all interview partners to identify potential controversies and consensus recommendations. RESULTS No controversies could be detected. On a variety of beneficial factors an interprofessional consensus between interview partners could be reached: A) The relevance of standardization of the screening for potential donors, the family approach and training; B) standards and best-practice procedures should be regulated and supervised by state authorities; C) full transparency and the prevention of scandals is essential; D) overburdened intensive care unit (ICU) doctors need to be supported by full-time in-house special nurses who organize donor evaluation, transport logistics and pastoral care, if required; E) public awareness campaigns are helpful; F) a broad public consensus on the concept of donation after brain and cardiac death is essential; G) incentives for the reporting of potential organ donors are inappropriate; H) an opt-out system alone is not sufficient. CONCLUSIONS Expert opinions from different professional backgrounds from different European health care systems reach a broad consensus on the most relevant issues for the improvement of organ donation.

Substrate-Independent Micropatterning of Polymer Brushes Based on Photolytic Deactivation of Chemical Vapor Deposition Based Surface-Initiated Atom-Transfer Radical Polymerization Initiator Films.

Precise microscale arrangement of biomolecules and cells is essential for tissue engineering, microarray development, diagnostic sensors, and fundamental research in the biosciences. Biofunctional polymer brushes have attracted broad interest in these applications. However, patterning approaches to creating microstructured biointerfaces based on polymer brushes often involve tedious, expensive, and complicated procedures that are specifically designed for model substrates. We report a substrate-independent, facile, and scalable technique with which to prepare micropatterned biofunctional brushes with the ability to generate binary chemical patterns. Employing chemical vapor deposition (CVD) polymerization, a functionalized polymer coating decorated with 2-bromoisobutyryl groups that act as atom-transfer radical polymerization (ATRP) initiators was prepared and subsequently modified using UV light. The exposure of 2-bromoisobutyryl groups to UV light with wavelengths between 187 and 254 nm resulted in selective debromination, effectively eliminating the initiation of ATRP. In addition, when coatings incorporating both 2-bromoisobutyryl and primary amine groups were irradiated with UV light, the amines retained their functionality after UV treatment and could be conjugated to activated esters, facilitating binary chemical patterns. In contrast, polymer brushes were selectively grown from areas protected from UV treatment, as confirmed by atomic force microscopy, time-of-flight secondary ion mass spectrometry, and imaging ellipsometry. Furthermore, spatial control over biomolecular adhesion was achieved in three ways: (1) patterned nonfouling brushes resulted in nonspecific protein adsorption to areas not covered with polymer brushes; (2) patterned brushes decorated with active binding sides gave rise to specific protein immobilization on areas presenting polymer brushes; (3) and primary amines were co-patterned along with clickable polymer brushes bearing pendant alkyne groups, leading to bifunctional reactivity. Because this novel technique is independent of the original substrate's physicochemical properties, it can be extended to technologically relevant substrates such as polystyrene, polydimethylsiloxane, polyvinyl chloride, and steel. With further work, the photolytic deactivation of CVD-based initiator coatings promises to advance the utility of patterned biofunctional polymer brushes across a spectrum of biomedical applications.

PhenoFluor: Practical Synthesis, New Formulation, and Deoxyfluorination of Heteroaromatics.

We report a practical synthesis method of the reagent PhenoFluor on decagram scale, provide a new formulation of PhenoFluor as a toluene solution, which should decrease challenges associated with the moisture sensitivity of the reagent, and expand the substrate scope of deoxyfluorination with PhenoFluor to heteroaromatics.

Inflammatory response against different carbon fiber-reinforced PEEK wear particles compared with UHMWPE in vivo.

Poly(ether ether ketone) (PEEK) and its composites are recognized as alternative bearing materials for use in arthroplasty because of their mechanical properties. The objective of this project was to evaluate the biological response of two different kinds of carbon fiber-reinforced (CFR) PEEK compared with ultra-high molecular weight polyethylene (UHMWPE) in vivo as a standard bearing material. Wear particles of the particulate biomaterials were injected into the left knee joint of female BALB/c mice. Assessment of the synovial microcirculation using intravital fluorescence microscopy as well as histological evaluation of the synovial layer were performed 7 days after particle injection. Enhanced leukocyte-endothelial cell interactions and an increase in functional capillary density as well as histological investigations revealed that all tested biomaterials caused significantly (P < 0.05) increased inflammatory reactions compared with control animals (injected with sterile phosphate-buffered saline), without any difference between the tested biomaterials (P > 0.05). These data suggest that wear debris of CFR-PEEK is comparable with UHMWPE in its biological activity. Therefore, CFR-PEEK represents an alternative bearing material because of its superior mechanical and chemical behavior without any increased biological activity of the wear particles, compared with a standard bearing material.