The multi-scale approach of masonry, paradigm of clay brick

Recent progress in nanoscience and engineering allows advanced characterization of materials. This type of characterization includes investigations revealing the scale dependent microstructure and mechanical as well physical properties of each component incorporated in the heterogeneous material. Its applicability and efficiency is confirmed in the field of cement based materials where the paradigm of these materials is solved, and universal buildings blocks and the multi-scale nature are well described. As a consequence, material researchers and engineers have knowledge about the impact of basic constituents and microstructure on macro behaviour of cement based materials. In the masonry field, a quite diverse situation is found. Although clay brick is among the oldest building materials, the main building blocks are still unknown. This knowledge gap is apparent in structural masonry, since the present homogenization and upscaling techniques consider only mortar joints, brick units and interface as a basic units. Here, the mechanical properties and elementary arrangement of these three components in the representative volume element (RVE) are assumed to govern the behaviour of masonry as a composite. But, it is understood that mortar may be broken down to lower scales, and its macro mechanical properties considered in the already developed approaches are governed by the lover scale components and its microstructure. Similarly, as it is shown by the authors in this contribution the brick unit may be broken down to lower scales, in which the basic material components and theirs properties are inherent. Therefore, the macro behaviour of composite masonry wall and its durability is considered to be ruled by the phenomena from the much lower scales present in the mortar, clay brick and the interface of these two

Multitechnique investigation of extruded clay brick microstructure

Despite the omnipresence of clay brick as construction material since thousands of years, fundamental knowledge about the link between composition, microstructure and mechanical performance is still scarce. In this paper, we employ a variety of advanced techniques of experimental mechanics and material characterization for extruded clay brick for masonry, that range from Scanning Electron Microscopy (SEM) coupled with Energy-dispersive X–ray Spectroscopy (EDX), Mercury Intrusion Porosimetry (MIP), to Instrumented Nanoindentation and macroscopic strength and durability tests. We find that extruded clay brick possesses a hierarchical microstructure: depending on the firing temperature, a “glassy” matrix phase, which manifests itself at sub-micrometer scales in form of neo-crystals of mullite, spinel-type phase and other accessory minerals, forms either a granular or a continuum matrix phase that hosts at sub-millimeter scale the porosity. This porous composite forms the backbone for macroscopic material performance of extruded brick, including anisotropic strength, elasticity and water absorption behavior.Authors gratefully acknowledge Portuguese Foundation for Science and Technology (FCT) for providing doctoral scholarship under the reference SFRH/BD/39232/2007 for Konrad J. Krakowiak. Special thanks to Dr. J. P. Castro Gomes, Centre of Materials and Building Technologies (C-MADE), University of Beira Interior for making feasible Mercury Intrusion measurements, as well as Dr. G. P. Souza for helpful guidance and advices related to this work

Meta-analysis of Queensland’s coastal Indigenous fisheries: examining the archaeological evidence for geographic and temporal patterning

Marine fisheries have been a critical part of Aboriginal and Torres Strait Islander people’s connection to land and sea country in Queensland, Australia for millennia. However, no archaeological studies have examined regional variability in the role of fish within subsistence regimes or the distribution of targeted fish species throughout the Holocene. We utilised a meta-analysis approach to conduct the first comprehensive assessment of Indigenous fisheries along the eastern Queensland coast. Data from 44 archaeological sites were grouped according to marine bioregion to facilitate broad comparison between sites across the study area. These sites were predominantly associated with mid-to-late Holocene occupation, and provided an assemblage of 45,052 recovered fish bones, of which 6,606 were identified most commonly to family-level. Results indicate clear geographic patterning in the ubiquity of fish species captured, and for some marine bioregions an increase through time in the range of species targeted. Archaeological data indicate mixed species fisheries, with a complex range of habitats and diverse fish species harvested by people in relative proximity to the sites. These harvesting decisions were mediated by local ecological knowledge, awareness of fish behaviour, and cultural preference for certain species. These outcomes support existing models for the region, which document a shift in subsistence regimes during the mid-to-late Holocene, particularly an increased reliance on marine resources and expansion in diet breadth. Future research needs to address geographic gaps in data availability and implement globally recognised ichthyoarchaeological quantification and identification protocols to comprehensively examine geographic and temporal variability in Queensland’s Holocene Indigenous fisheries, and contribute to regional models of long-term subsistence change

Precise Experimental Investigation of Eigenmodes in a Planar Ion Crystal

The accurate characterization of eigenmodes and eigenfrequencies of two-dimensional ion crystals provides the foundation for the use of such structures for quantum simulation purposes. We present a combined experimental and theoretical study of two-dimensional ion crystals. We demonstrate that standard pseudopotential theory accurately predicts the positions of the ions and the location of structural transitions between different crystal configurations. However, pseudopotential theory is insufficient to determine eigenfrequencies of the two-dimensional ion crystals accurately but shows significant deviations from the experimental data obtained from resolved sideband spectroscopy. Agreement at the level of 2.5 x 10^(-3) is found with the full time-dependent Coulomb theory using the Floquet-Lyapunov approach and the effect is understood from the dynamics of two-dimensional ion crystals in the Paul trap. The results represent initial steps towards an exploitation of these structures for quantum simulation schemes.Comment: 5 pages, 4 figures, supplemental material (mathematica and matlab files) available upon reques

Sustainable harvesting of Conomurex luhuanus and Rochia nilotica by Indigenous Australians on the Great Barrier Reef over the past 2000 years

Offshore island colonisation and use around the northern Australian coastline in the mid-to-late Holocene is associated with expanding Aboriginal and Torres Strait Islander populations and intensifying land-use activities. However, few explicit tests of the long-term effects of shellfish forager decision-making and associated impacts on intertidal ecosystems in these newly colonised island environments have been undertaken. We report morphometric analyses on two key reef flat Great Barrier Reef shellfish species, strawberry conch Conomurex luhuanus (n = 360) and top shell Rochia nilotica (n = 45), from two late Holocene archaeological shell midden assemblages on Lizard Island, northeast Queensland. Human foraging pressure was assessed through reconstructions of population age structure across time, highlighting the importance of determining size-at-age habitat preferences and species behaviour patterns when assessing long-term anthropogenic impacts on shellfish populations. Results show no evidence for resource depression across the late Holocene which is broadly in keeping with previous findings at other locales on the Great Barrier Reef, but contrary to expectations of resource intensification models. We conclude that the rich and abundant resources of reef flat environments were resilient to relatively low intensity and likely episodic Indigenous foraging. This sustainability contrasts with the scale and impacts of intensive industrialised harvesting in the historic period

IL-6 Plasma Levels Correlate With Cerebral Perfusion Deficits and Infarct Sizes in Stroke Patients Without Associated Infections

Introduction: We aimed to investigate several blood-based biomarkers related to inflammation, immunity, and stress response in a cohort of patients without stroke-associated infections regarding their predictive abilities for functional outcome and explore whether they correlate with MRI markers, such as infarct size or location. Methods: We combined the clinical and radiological data of patients participating in two observational acute stroke cohorts: the PREDICT and 1000Plus studies. The following blood-based biomarkers were measured in these patients: monocytic HLA-DR, IL-6, IL-8, IL-10, LBP, MRproANP, MRproADM, CTproET, Copeptin, and PCT. Multiparametric stroke MRI was performed including T2*, DWI, FLAIR, TOF-MRA, and perfusion imaging. Standard descriptive sum statistics were used to describe the sample. Associations were analyzed using Fischer's exact test, independent samples t-test and Spearmans correlation, where appropriate. Results: Demographics and stroke characteristics were as follows: 94 patients without infections, mean age 68 years (SD 10.5), 32.2% of subjects were female, median NIHSS score at admission 3 (IQR 2-5), median mRS 3 months after stroke 1 (IQR 0-2), mean volume of DWI lesion at admission 5.7 ml (SD 12.8), mean FLAIR final infarct volume 10 ml (SD 14.9), cortical affection in 61% of infarctions. Acute DWI lesion volume on admission MRI was moderately correlated to admission/maximum IL-6 as well as maximum LBP. Extent of perfusion deficit and mismatch were moderately correlated to admission/maximum IL-6 levels. Final lesion volume on FLAIR was moderately correlated to admission IL-6 levels. Conclusion: We found IL-6 to be associated with several parameters from acute stroke MRI (acute DWI lesion, perfusion deficit, final infarct size, and affection of cortex) in a cohort of patients not influenced by infections

Suppression of Superconductivity in YBCO/LCMO Superlattices

The competition of superconductivity and magnetism in superlattices composed of alternating YBa$_2$Cu$_3$O$_{7-d}$ and La$_{0.67}$Ca$_{0.33}$MnO$_{3}$ thin films is investigated using low-energy optical spectroscopy. The thickness of the superconducting YBCO layers is varied from 30 nm to 20 nm while the thickness of the magnetic LCMO layers is kept constant at 20 nm. We clearly observe that the superconducting condensate density in the superconducting state of superlattice is drastically reduced by the magnetic subsystem which may be connected with proximity effects that distort the gap symmetry and thus suppress superconductivity.Comment: 4 pages, 4 figure

Direct radiocarbon dating of fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) from Long Point, Coorong, South Australia

Accelerator Mass Spectrometry (AMS) radiocarbon dates (n=20) determined on fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) are reported from five sites at Long Point, Coorong, South Australia. The dates range from 2938–2529 to 326–1 cal. BP, extending the known period of occupation of Long Point. Previous dating at the sites indicated intensive occupation of the area from 2455–2134 cal. BP. Results provide a detailed local chronology for the region, contributing to a more comprehensive understanding of Aboriginal use of Ngarrindjeri lands and waters. This study validates the use of fish otoliths for radiocarbon dating and reveals how dating different materials can result in different midden chronologies