Logo

Publikacije (139)

Nazad
A. Masic, Marco Nicola

The unique NIR luminescence of the ancient pigments Egyptian Blue, Han Blue and Han Purple [1] has recently attracted significant interest because its existence allows fast identification these pigments even when present in minimal amounts and using non-destructive tools [2]. A more comprehensive study of this feature associated also to micro-imaging and compositional evaluations can be used as a mean to improve archaeometric studies about production technologies [3], giving also useful data to hint the provenance of the pigments and their trade routes. The three pigments, and especially Egyptian Blue (EB) were widely used in a large span of years and places. Indeed, EB was invented during the 4th millennium BCE [4] and until Middle Ages has been by far the most used blue pigment in all the Mediterranean Basin and the Near East. It was first produced probably in Egypt from where it has been heavily traded to many Mediterranean countries. However the technology of production evolved in time and spread in different places such as Mesopotamia and Italy [5]. EB invention is related to the development of close related materials such as pottery, bronze and especially glass and Egyptian faience. A large part of Egyptian faience is light blue (LBEF) and its color is to copper LBEF glaze and other glassy materials are intimately linked EB that they can show almost the same color and share a very similar elemental composition. The differences between EB and the outer layer of LBEF may relay mainly on the production technology used. However, from a chemical stand point the main difference is that EB has a structure made of CaCuSi4O10 (cuprorivaite) crystals embedded in an amorphous matrix rich in Na or K, while LBEF glaze and Cu-rich glasses are a glassy phase made of Si, Ca and O, rich in Na and/or K from the

Hyun-Chae Loh, Hee-Jeong Kim, F. Ulm, A. Masic

Concrete is one of the most used materials in the world, second only to water. One of the key advantages of this versatile material is its workability in the early stages before setting. Here, we use in situ underwater Raman microspectroscopy to investigate and visualize the early hydration kinetics of ordinary Portland cement (OPC) with submicron spatial and high temporal resolution. First, the spectral features of the C-S-H gel were analyzed in the hydroxyl stretching region to confirm the coexistence of Ca-OH and Si-OH bonds in a highly disordered C-S-H gel. Second, the disordered calcium hydroxide (Ca(OH)2) is experimentally identified for the first time in the mixture before setting, suggesting that Ca(OH)2 crystallization and growth are essential in the setting of cement paste. Finally, the phase transformations of clinker, C-S-H, and Ca(OH)2 are spatially and temporally resolved, and the hydration kinetics are studied by analyzing the spatial relationships of these phases using two-point correlation functions. The results quantitatively validate that the setting occurs as a percolation process, wherein the hydration products intersect and form an interconnected network. This time-space-resolved characterization method can map and quantitatively analyze the heterogeneous reaction of the cementitious colloidal system and thus provide potential application value in the field of cement chemistry and materials design more broadly.

K. Faber, F. Casadio, A. Masic, L. Robbiola, M. Walton

Cultural heritage materials, ranging from archaeological objects and sites to fine arts collections, are often characterized through their life cycle. In this review, the fundamentals and tools of materials science are used to explore such life cycles—first, via the origins of the materials and methods used to produce objects of function and artistry, and in some cases, examples of exceptional durability. The findings provide a window on our cultural heritage. Further, they inspire the design of sustainable materials for future generations. Also explored in this review are alteration phenomena over intervals as long as millennia or as brief as decades. Understanding the chemical processes that give rise to corrosion, passivation, or other degradation in chemical and physical properties can provide the foundation for conservation treatments. Finally, examples of characterization techniques that have been invented or enhanced to afford studies of cultural heritage materials, often nondestructively, are highlighted.

Linda M Seymour, D. Keenan‐Jones, G. Zanzi, A. Masic

Ancient Roman concrete constitutes many ancient structures that remain standing; however, little is known about how it has remained durable. Here, we investigate the mortars used in ancient water bearing infrastructure such as aqueducts, cisterns, and baths. In these structures, crushed ceramics are used as a pozzolanic additive on surfaces in continuous or frequent contact with water. The ceramic-lime mortars are probed using a multi-scale characterization approach including SEM-EDS and Raman microspectroscopy. The analysis shows the role of ceramics within these structures as a source of aluminosilicates, mapping the presence of both pozzolanic and post-pozzolanic phases. A hybrid binder consisting of cementitious hydrates and calcite is mapped at the interface of the ceramics and evidence of post-pozzolanic densification of pores and cracks is observed. Comparison across structures shows that material selection and chemistry benefit the infrastructure applications. Understanding these ancient materials provides inspiration for new, durable infrastructure materials.

Samuel J. Raymond, Janille M. Maragh, A. Masic, John R. Williams

This paper explores the use of the meshfree computational mechanics method, the Material Point Method (MPM), to model the composition and damage of typical renal calculi, or kidney stones. Kidney stones are difficult entities to model due to their complex structure and failure behavior. Better understanding of how these stones behave when they are broken apart is a vital piece of knowledge to medical professionals whose aim is to remove these stone by breaking them within a patient’s body. While the properties of individual stones are varied, the common elements and proportions are used to generate synthetic stones that are then placed in a digital experiment to observe their failure patterns. First a more traditional engineering model of a Brazil test is used to create a tensile fracture within the center of these stones to observe the effect of stone consistency on failure behavior. Next a novel application of MPM is applied which relies on an ultrasonic wave being carried by surrounding fluid to model the ultrasonic treatment of stones commonly used by medical practitioners. This numerical modeling of Extracorporeal Shock Wave Lithotripsy (ESWL) reveals how these different stones failure in a more real-world situation and could be used to guide further research in this field for safer and more effective treatments.

Linda M Seymour, Marco Nicola, Max I Kessler, Claire L Yost, Alessandro Bazzacco, Alessandro Marello, E. Ferraris, R. Gobetto et al.

The ancient pigment Egyptian blue has long been studied for its historical significance; however, recent work has shown that its unique visible induced luminescent property can be used both to identify the pigment and to inspire new materials with this characteristic. In this study, a multi-modal characterization approach is used to explore variations in ancient production of Egyptian blue from shabti statuettes found in the village of Deir el-Medina in Egypt (Luxor, West Bank) dating back to the New Kingdom (18th-20th Dynasties; about 1550–1077 BCE). Using quantitative SEM-EDS analysis, we identify two possible production groups of the Egyptian blue and demonstrate the presence of multiple phases within samples using cluster analysis and ternary diagram representations. Using both macro-scale non-invasive (X-rays fluorescence and multi-spectral imaging) and micro-sampling (SEM-EDS and Raman confocal microspectroscopy) techniques, we correlate photoluminescence and chemical composition of the ancient samples. We introduce Raman spectroscopic imaging as a means to capture simultaneously visible-induced luminesce and crystal structure and utilize it to identify two classes of luminescing and non-luminescing silicate phases in the pigment that may be connected to production technologies. The results presented here provide a new framework through which Egyptian blue can be studied and inform the design of new materials based on its luminescent property.

BACKGROUND Multiple sclerosis (MS) as chronic neurodegenerative disease significantly impact patients' quality of life (QoL). QoL instruments can be generic (EQ-5D, SF-36) and disease-specific like MSQoL-54. Use of disease-specific instruments is preferred since it captures broader symptoms related to MS than generic instruments. Mental health is impacted by MS and different psychiatric conditions significantly impact QoL. We have conducted prospective non-interventional study among MS patients. Aim was to measure and compare MS patients QoL by generic and disease-specific instrument at baseline and after one year and to identify potential correlation between these two types of measurements and to assess mental health scores among MS patients in Bosnia and Herzegovina (B&H) and other countries. SUBJECTS AND METHODS Study included 62 patients diagnosed with MS and treated at Neurology clinic in Sarajevo from April 2016 to May 2017. Study was approved by Ethical Committee. QoL has been measured by EQ-5D and MSQoL-54. Measurement has been performed at baseline and after 12 months. RESULTS Average utility score measured by EQ-5D at the baseline and end of the study were 0.688 and 0.639 respectively with no significant difference (p=0.850). EQ-5D utility and MSQoL-54 score showed high correlation at baseline; rho=0.873 p=0.0001 for physical health and rho=0.711 p=0.0001 for mental health. At the end of the study no significant correlations have been found (p>0.05). High negative correlation found between EDSS and scores measured by EQ-5D and MSQoL-54; at baseline (rho=-0.744 p=0.0001) and at the end of the study (rho=-0.832 p=0.0001). Similar MS impact and loss of QoL found in B&H and other countries. CONCLUSIONS Both instruments can be used in measuring QoL but disease-specific are preferred since they capture broader symptoms impacting MS patient QoL. Using QoL instruments could drive clinician decision and patient-centric care as well as reimbursement and policy decision by recording treatment outcomes.

Jennifer L. Meanwell, E. Paris, Carlos Peraza Lope, Linda M Seymour, A. Masic

This study presents evidence of two tuyères, or blowpipe tips, used in metalworking at the Postclassic period city of Mayapán. Blowpipe technology has long been hypothesized to be the production technique for introducing oxygen to furnaces during the metal casting process on the basis of ethnohistorical depictions of the process in ancient Mesoamerica. To our knowledge, the tuyères recovered at Mayapán are the first archaeologically documented tuyères for pre-Hispanic Mesoamerica. The dimensions, internal perforation, vitrification, and presence of copper prills within the ceramic fabric, suggest that they were used in pyrotechnological production, likely metalworking, and is consistent with previous evidence for small-scale metalworking at Mayapán. Blowpipe use in metallurgical production is a logical extension of a much longer tradition of blowgun use in hunting, which was likely already present in Mesoamerica by the time metal was introduced to West Mexico from South America. Furthermore, the dimensions of the Mayapán tuyères are consistent with the internal diameter of ethnohistorically-documented blowguns from Jacaltenango in the southwest Maya region. We conducted replication experiments that suggest that when combined with wooden blowpipes, the Mayapán tuyères would have been ideal for small-scale, furnace-based metallurgy, of the type identified at Mayapán from Postclassic period contexts.

Gabriele Grezzana, Hyun-Chae Loh, Zhao Qin, M. Buehler, A. Masic, F. Libonati

The fibrillar organization is crucial for the mechanics of osteonal bone and for its anisotropy. Different collagen fiber orientation (CFO) patterns are observed in bone and correlated to the main local loading, leading to the hypothesis that the fibers are preferentially aligned to bear specific loading types. A heterogeneous distribution of osteon morphotypes (OMs) is noticed in long bones, although the relationship between the OM spatial distribution and the local predominant loading is still unclear. This study aims to shed light on the reasons why Nature uses specific OMs in diverse stress‐dominated regions. A multimodal approach is adopted, including collagen fiber orientation mapping, numerical modeling of different OMs under tensile and compressive loading, and 3D‐printing of OM‐inspired samples, to unravel the relationship between different OMs and their mechanical behavior. Simulation results suggest a better performance of the vertical OM (VOM) under tensile loading and of the twisted OM (TOM) under compression, confirming earlier hypotheses. The outcomes of mechanical testing, conducted on 3D‐printed samples, highlight a possible buckling‐induced failure of fibers with preferential vertical orientation and provide evidence that OMs are stress‐tailored, opening new venues for the design of stress‐tuned bioinspired composites.

C. Wan, D. López Barreiro, A. Forner‐Cuenca, Jack-William Barotta, Morgan J. Hawker, G. Han, Hyun-Chae Loh, A. Masic et al.

Increasing redox reaction rates on carbon electrodes is an important step to reducing the cost of all-vanadium redox flow batteries (VRFBs). Biomass-derived activated carbons (ACs) hold promise as ...

Roman Schuetz, Janille M. Maragh, J. Weaver, I. Rabin, A. Masic

Analysis of the Temple Scroll reveals another technology used to produce the Dead Sea Scrolls and potential preservation concerns. The miraculously preserved 2000-year-old Dead Sea Scrolls, ancient texts of invaluable historical significance, were discovered in the mid-20th century in the caves of the Judean desert. The texts were mainly written on parchment and exhibit vast diversity in their states of preservation. One particular scroll, the 8-m-long Temple Scroll is especially notable because of its exceptional thinness and bright ivory color. The parchment has a layered structure, consisting of a collagenous base material and an atypical inorganic overlayer. We analyzed the chemistry of the inorganic layer using x-ray and Raman spectroscopies and discovered a variety of evaporitic sulfate salts. This points toward a unique ancient production technology in which the parchment was modified through the addition of the inorganic layer as a writing surface. Furthermore, understanding the properties of these minerals is particularly critical for the development of suitable conservation methods for the preservation of these invaluable historical documents.

Nema pronađenih rezultata, molimo da izmjenite uslove pretrage i pokušate ponovo!

Pretplatite se na novosti o BH Akademskom Imeniku

Ova stranica koristi kolačiće da bi vam pružila najbolje iskustvo

Saznaj više