Search

This study reports the use of 1-butyl-3-methyl imidazolium methanesulfonate ionic liquid as a template in the synthesis of zeolites. It is found that the silicon source determines the formation of beta (BEA), mordenite framework inverted (MFI), or analcime (ANA) zeolites. Depending on this source, different preorganized complexes are obtained that drive the formation of the different zeolite structures. In the presence of ethanol, the ionic liquid form preorganized complexes that drive the formation of MFI. In its absence, BEA is obtained. Whereas, the large amount of sodium present when using sodium metasilicate leads to ANA formation. A molecular simulation study of the relative stability of the template-framework system and location of the template provides further insight into the mechanism of synthesis. [ABSTRACT FROM AUTHOR]

The present study proposes an important contribution to the understanding of ionic liquid role as structure directing agent for zeolite synthesis. A series of imidazolium based ionic liquids are used for this purpose. While the anionic counterpart influences the micellar organization during the synthesis, the imidazolium cation clearly directs the structure to one or another zeolite family as a function of its substituents and their interaction with the zeolite framework. The experimental observations are contrasted with molecular modeling explaining the distinct zeolite families obtained on the basis of different preferential orientation of the ionic liquids to the Si 33 precursor. [Display omitted] • The imidazolium cation clearly directs the zeolite structure to one or another family. • TON structure is observed when [Emim]+ is used as template unlike for [Bmim]+ and [Hexmim]+ where MFI was the main phase. • Computational results shown that [Emim]+ had a preferential orientation respect to the Si 33 precursor leading to TON structure. [ABSTRACT FROM AUTHOR]

Research on personal adornments depends on the reliable characterisation of materials to trace provenance and model complex social networks. However, many analytical techniques require the transfer of materials from the museum to the laboratory, involving high insurance costs and limiting the number of items that can be analysed, making the process of empirical data collection a complicated, expensive and time-consuming routine. In this study, we compiled the largest geochemical dataset of Iberian personal adornments (n = 1243 samples) by coupling X-ray fluorescence compositional data with their respective X-ray diffraction mineral labels. This allowed us to develop a machine learning-based framework for the prediction of bead-forming minerals by training and benchmarking 13 of the most widely used supervised algorithms. As a proof of concept, we developed a multiclass model and evaluated its performance on two assemblages from different Portuguese sites with current mineralogical characterisation: Cova das Lapas (n = 15 samples) and Gruta da Marmota (n = 10 samples). Our results showed that decisión-tres based classifiers outperformed other classification logics given the discriminative importance of some chemical elements in determining the mineral phase, which fits particularly well with the decision-making process of this type of model. The comparison of results between the different validation sets and the proof-of-concept has highlighted the risk of using synthetic data to handle imbalance and the main limitation of the framework: its restrictive class system. We conclude that the presented approach can successfully assist in the mineral classification workflow when specific analyses are not available, saving time and allowing a transparent and straightforward assessment of model predictions. Furthermore, we propose a workflow for the interpretation of predictions using the model outputs as compound responses enabling an uncertainty reduction approach currently used by our team. The Python-based framework is packaged in a public repository and includes all the necessary resources for its reusability without the need for any installation. [ABSTRACT FROM AUTHOR]

The discovery of a set of beads, comprising both Sicilian amber and resin-coated beads in the Middle Bronze Age burial site of Cova del Gegant (Sitges, Barcelona, Spain), has sparked inquiries into whether the coating was intended for imitation or counterfeiting of amber. We assert that human-made materials, such as bead coatings, are intentionally conceived, designed, and crafted to fulfill specific functions. Thus, for an object to effectively fulfill its intended purpose, it must meet particular performance criteria influenced by situational factors. This paper aims to construct an empirically grounded narrative elucidating the development and function of resin-coated bead technology. Our methodology includes a comprehensive quantitative analysis of the coating and beads, an exploration of the interplay between technical choices and situational factors, and an investigation into whether the simulation of sensory performance characteristics played a pivotal role in the concept and design of resin-coated beads. Additionally, we synthesize data to unveil broader patterns related to the crafting and utilization of resin-coated and amber beads across time and space. We have documented resin-coated beads in the Iberian Peninsula from the Neolithic period (5th to 3rd millennia BCE) until at least the Middle Bronze Age (first half of the 2nd millennium BCE), where they coexisted with amber beads. Analysis employing ATR-FTIR and μ-CT imaging has revealed a composite coating comprising pine resin, beeswax, and carotene, adhered to shell beads with bone glue. This composite material represents the earliest known development in human history, unique to the Iberian Peninsula and without parallel in Prehistoric Europe. Our examination of the performance characteristics and functional roles of resin-coated beads suggests their potential as substitutes for amber beads, particularly in regions where amber was scarce or inaccessible. Despite being crafted from commonplace materials, these coated beads exhibit intentional design choices likely aimed at simulating the visual performance characteristics of amber. This deliberate effort, alongside their widespread distribution across time and space, indicates that composite-coated beads held symbolic and social significance akin to amber beads. • Our study quantitatively examines the development of coated beads in prehistoric Iberia, offering a thorough hypothesis of their past function and use. • Our study uses ATR-FTIR and μ-CT scans for a comprehensive analysis of these artifacts' composition and structure, appealing to a broad audience. • Our findings show the oldest evidence of humanmade composite material, bonded to a shell by bone glue, indicating advanced prehistoric design. • We uncover how these beads were designed to visually mimic amber, aiming for a specific color and aging process. • Our study highlights the social and symbolic significance of amber-like beads in high-status adornment, analyzing factors driving this technology. • The Tagus estuary concentration of these beads suggests a nuanced understanding of genuine amber scarcity and the need for innovative adornment technology. [ABSTRACT FROM AUTHOR]

The study of adornments found in the necropolis at Valle de las Higueras (Huecas, Toledo) has determined the morphotypology and mineral composition of one quadrangular pendant and 341 stone beads. Most of the beads are short (length = 5 mm), but within this regularity series can be differentiated that might be the result of standardised fabrication processes and different times of acquisition. Portable X-ray fluorescence (p-XRF) and X-ray diffraction (XRD) analysis identified the use of phyllosilicates as sepiolite and clinochlore, and above all variscite, a mineral that became especially important for adornments in the Iberian Peninsula in the 3rd millennium BC. The inland location of the necropolis, distant from source areas, certifies its remote origin, as far away as northwest Zamora according to the chronological framework. It is still not possible to determine for sure the source of the variscite at Valle de las Higueras. However, the inland location of the necropolis, distant from source areas, certifies its remote origin. The chronology suggests that it might have come from the north-west, in the area of Zamora. Archaeological and chronological data obtained in tombs in the necropolis, together with other inland sites, contribute to understanding variscite circulation in the Iberian Peninsula in the Chalcolithic. It was restricted to a few individuals, both adults and children, who wore necklaces and bracelets. Distance did not condition the arrival of variscite, but the small amounts suggest it was traded together with other ostentation elements, such as sea shells, cinnabar and amber. The heterogeneous regional panorama displays differences in the demand, use and acquisition of variscite depending on the socioeconomic organisation and connection to exchange networks. [ABSTRACT FROM AUTHOR]

A group of beads from the artificial cave of La Molina (Lora de Estepa, Sevilla) and Cova del Gegant (Sitges, Barcelona) were made from a biogenic raw material and intentionally covered by a layer of resin. This is the first time this type of treatment has been documented on elements of adornment in the Late Prehistory of the Iberian Peninsula. The composition and nature of the coatings are analysed and the symbolic role of such alterations and imitations of prehistoric adornments is discussed. [ABSTRACT FROM AUTHOR]

The identification of archaeological amber has been used in Iberian prehistory to evidence long-distance exchanges and engage Iberia in networks that connect western Europe with central and northern Europe, the emergence of social complexity, and the consolidation of trade networks. However, until now, no comprehensive analytical study of the Iberian amber has been produced to support any of the interpretive models currently in use. This paper approaches the analysis of Iberian Peninsula amber artefacts by considering their provenance (based on FTIR characterization), chronology, and spatial relationship with other exotica. Our work increases the number of analyzed artefacts to 156 (24%), out of the c. 647 currently known for the Iberian Peninsula. Based on these new data and a review of Murillo-Barroso and Martinón-Torres (2012), this overview outlines amber consumption patterns from the 6th to 2nd millennia BCE and demonstrates long-distance amber exchange connecting Iberia with the Mediterranean region from the Neolithic period onwards. [ABSTRACT FROM AUTHOR]