Mechanisms of reduced implant stability in osteoporotic bone

The determining factors for the fixation of uncemented screws in bone are the bone-implant interface and the peri-implant bone. The goal of this work was to explore the role of the peri-implant bone architecture on the mechanics of the bone-implant system. In particular, the specific aims of the study were to investigate: (i) the impact of the different architectural parameters, (ii) the effects of disorder, and (iii) the deformations in the peri-implant region. A three-dimensional beam lattice model to describe trabecular bone was developed. Various microstructural features of the lattice were varied in a systematic way. Implant pull-out tests were simulated, and the stiffness and strength of the bone-implant system were computed. The results indicated that the strongest decrease in pull-out strength was obtained by trabecular thinning, whereas pull-out stiffness was mostly affected by trabecular removal. These findings could be explained by investigating the peri-implant deformation field. For small implant displacements, a large amount of trabeculae in the peri-implant region were involved in the load transfer from implant to bone. Therefore, trabecular removal in this region had a strong negative effect on pull-out stiffness. Conversely, at higher displacements, deformations mainly localized in the trabeculae in contact with the implant; hence, thinning those trabeculae produced the strongest decrease in the strength of the system. Although idealized, the current approach is helpful for a mechanical understanding of the role played by peri-implant bon

Experimental exploration of the origin of magnetostriction in single crystalline iron

The magnetostrictive atomic strain in a pure Fe single crystal was measured by differential x-ray absorption spectroscopy. The obtained tetragonal magnetostriction constant, (3/2)λ100, was determined to be 45 ppm, consistent with the previously reported theoretical value calculated from a spin-orbit coupling theory. These results provide a foundation for understanding the origin of magnetostriction in pure Fe as well as Fe-based binary alloys

Fracture of Polyjet 3D printed materials: a preliminary investigation

Additive manufacturing (AM), in particular 3D printing, gained a lot of interest in the past few years. This work is focused in particular on the Polyjet 3D process by means of which photo-curable polymers with strongly different physical and mechanical properties can be injected (in the form of liquid droplets) and cured through the use of a UV lamp. In previous works [1,2] we already highlighted the important influence that the interphase between different constituents can have on the viscoelastic properties of the 3D printed composite materials. In view of extending our research beyond small deformations and towards the determination of the fracture properties of Polyjet composites, a preliminary investigation was carried out to characterize the fracture behaviour of base constituents, and to verify the applicability of conventional fracture mechanics approaches to this particular class of AM materials/structures. As a first step, the effect of several parameters on the apparent fracture properties was determined: material composition (rubber content), printing orientation, presence of support material and ageing time. For this study, two polymers were considered: VeroWhitePlus (RGD835) and VeroGray (RGD850). They both share the same glassy matrix, but VeroGray also includes a secondary rubbery phase. Tensile and scratch experiments were performed to evaluate bulk and surface mechanical properties, later to be considered as a basis to analyze fracture data obtained on three point bending notched samples, tested according to ISO 13586 to determine apparent toughness and fracture energy values, KIC and GIC. The applicability of a fracture mechanics framework to these materials was discussed

The mineralization of osteonal cement line depends on where the osteon is formed

The cement line (CL) is a thin layer, 1-3 μm in width, separating secondary osteons from interstitial bone and other osteons. Despite the possible role for bone quality, the CL is still one of the least understood features of bone. This study aims to investigate how the mineral content of the CL varies not only with osteon age but also with the surrounding environment. Using quantitative backscattered electron imaging to measure the mineral content, we analyzed 35 osteons from femoral bone of two male individuals (40 and 81 yr old). We implemented a new approach to investigate the mineral content based on a spatially resolved analysis in layers along the CL and incorporating regions both inside the osteon (formed soon after CL deposition) and outside (already present at the time of CL deposition). We found that the CLs had always higher mineral content than the corresponding osteon (p < .001), and that not only the osteon, but also the CL increases its mineral content with time. Including areas outside the osteon in the analysis improved considerable our understanding of CL mineralization. After a rapid primary phase where the CL incorporates more mineral than the osteon, secondary mineralization is about 60% slower in the CL than in the osteon. One key finding is that the mineralization of the CL is not universal but depends on the region in which the osteon is formed. This is supported by a strong correlation between the mineral content of the CL and outside the osteon (R = 0.75, p < .001), but not inside. One possible explanation is that mineral released during bone resorption may contribute to the mineralization of the cement line, as higher mineral content in resorbed bone was associated with greater mineralization in the cement line

Practical and regioselective amination of arenes using alkyl amines

© 2019 Crown. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted Manuscript version of a Published Work that appeared in final form in Nature Chemistry. To access the final edited and published work see https://doi.org/10.1038/s41557-019-0254-5The formation of carbon–nitrogen bonds for the preparation of aromatic amines is among the top five reactions carried out globally for the production of high-value materials, ranging from from bulk chemicals to pharmaceuticals and polymers. As a result of this ubiquity and diversity, methods for their preparation impact the full spectrum of chemical syntheses in academia and industry. In general, these molecules are assembled through the stepwise introduction of a reactivity handle in place of an aromatic C–H bond (that is, a nitro group, halogen or boronic acid) and a subsequent functionalization or cross-coupling. Here we show that aromatic amines can be constructed by direct reaction of arenes and alkyl amines using photocatalysis, without the need for pre-functionalization. The process enables the easy preparation of advanced building blocks, tolerates a broad range of functionalities, and multigram scale can be achieved via a batch-to-flow protocol. The merit of this strategy as a late-stage functionalization platform has been demonstrated by the modification of several drugs, agrochemicals, peptides, chiral catalysts, polymers and organometallic complexes

Plant cell culture technology in the cosmetics and food industries : current state and future trends

The production of drugs, cosmetics, and food which are derived from plant cell and tissue cultures has a long tradition. The emerging trend of manufacturing cosmetics and food products in a natural and sustainable manner has brought a new wave in plant cell culture technology over the past 10 years. More than 50 products based on extracts from plant cell cultures have made their way into the cosmetics industry during this time, whereby the majority is produced with plant cell suspension cultures. In addition, the first plant cell culture-based food supplement ingredients, such as Echigena Plus and Teoside 10, are now produced at production scale. In this mini review, we discuss the reasons for and the characteristics as well as the challenges of plant cell culture-based productions for the cosmetics and food industries. It focuses on the current state of the art in this field. In addition, two examples of the latest developments in plant cell culture-based food production are presented, that is, superfood which boosts health and food that can be produced in the lab or at home

Spatial and Temporal Variations in the Annual Pollen Index Recorded by Sites Belonging to the Portuguese Aerobiology Network

This study presents the findings of a 10-year survey carried out by the Portuguese Aerobiology Network (RPA) at seven pollen-monitoring stations: five mainland stations (Oporto, Coimbra, Lisbon, Évora and Portimão) and two insular stations [Funchal (Madeira archipelago) and Ponta Delgada (Azores archipelago)]. The main aim of the study was to examine spatial and temporal variations in the Annual Pollen Index (API) with particular focus on the most frequently recorded pollen types. Pollen monitoring (2003–2012) was carried out using Hirst-type volumetric spore traps, following the minimum recommendations proposed by the European Aerobiology Society Working Group on Quality Control. Daily pollen data were examined for similarities using the Kruskal–Wallis nonparametric test and multivariate regression trees. Simple linear regression analysis was used to describe trends in API. The airborne pollen spectrum at RPA stations is dominated by important allergenic pollen types such as Poaceae, Olea and Urticaceae. Statistically significant differences were witnessed in the API recorded at the seven stations. Mean API is higher in the southern mainland cities, e.g. Évora, Lisbon and Portimão, and lower in insular and littoral cities. There were also a number of significant trends in API during the 10-year study. This report identifies spatial and temporal variations in the amount of airborne pollen recorded annually in the Portuguese territory. There were also a number of significant changes in API, but no general increases in the amount of airborne pollen