Raman investigation of corrosion products on Roman copper-based artefacts

This paper illustrates a case study related to the characterisation of corrosion products present on recently excavated artefacts. The archaeological findings, from the Rakafot 54 site (Beer-Sheva, Israel), consist of 23 coins and a pendant, all dating back to the Roman period. Raman spectroscopy was used to identify the corrosion products that compose the patina covering the objects. To facilitate and support their identification, spectra were then processed using principal components analysis. This chemometric technique allowed the identification of two main compounds, classified as atacamite and clinoatacamite, which formed the main components of the patinas. The results of this investigation can help in assessing the conservation state of artefacts and defining the correct restoration strategy

Non-invasive characterization of ancient Cu-based coins using Raman spectroscopy

Characterization of archaeological finds is a challenging case study for researchers, as the need of non-invasive measurements strongly affects the investigation strategies. Moreover, it is almost not possible to follow a fixed protocol, because the measurement conditions should be tailored to the samples under study. This paper presents a preliminary characterization of bronze coins coming from an archaeological site located in the south of Israel. The superficial corrosion layers have been analysed by means of Raman spectroscopy in order to investigate their composition and assess the conservation state of the finds. Reference samples of known composition have also been used to help peaks identification in the Raman spectra. Results coming from this study can help in defining the correct conservation strategies for the artefacts

Characterisation of Roman copper alloy artefacts and soil from Rakafot 54 (Beer Sheva, Israel)

The research presented in this paper focused on the preliminary non-destructive analysis of copper alloys, corrosion, and soil components from a Roman archaeological site in Israel. pXRF, XRD, and micromorphological analyses were carried out to gain a better understanding of the corrosion processes affecting the copper alloy artefacts, by characterising the alloy composition, soil environments, and corrosion products. Preliminary results indicate that the artefacts consist of copper-lead-tin alloys, covered by copper hydroxy-chlorides and lead sulphate phases with slight variations in their crystallisation. The multi-analytical approach revealed the presence of quartz, calcite, gypsum and feldspars in the sediments, while thin sections more specifically indicate loess soils with local micro-environments

Direct Measurement of the System-Environment Coupling as a Tool For Understanding Decoherence and Dynamical Decoupling

Decoherence is a major obstacle to any practical implementation of quantum information processing. One of the leading strategies to reduce decoherence is dynamical decoupling --- the use of an external field to average out the effect of the environment. The decoherence rate under any control field can be calculated if the spectrum of the coupling to the environment is known. We present a direct measurement of the bath coupling spectrum in an ensemble of optically trapped ultracold atoms, by applying a spectrally narrow-band control field. The measured spectrum follows a Lorentzian shape at low frequencies, but exhibits non-monotonic features at higher frequencies due to the oscillatory motion of the atoms in the trap. These features agree with our analytical models and numerical Monte-Carlo simulations of the collisional bath. From the inferred bath-coupling spectrum, we predict the performance of well-known dynamical decoupling sequences: CPMG, UDD and CDD. We then apply these sequences in experiment and compare the results to predictions, finding good agreement in the weak-coupling limit. Thus, our work establishes experimentally the validity of the overlap integral formalism, and is an important step towards the implementation of an optimal dynamical decoupling sequence for a given measured bath spectrum.Comment: 9 pages, 6 figure

Raman and micromorphological characterization of carbonates in plaster-like materials from the Natufian site of Eynan (Ain Mallaha), Israel

The archaeological site of Eynan, located by the spring of Ain Mallaha and on the shores of Lake Hula in the Upper Jordan Valley, Israel, existed for several millennia at the end of the Pleistocene. During the Natufian culture of the Levantine Epipalaeolithic, the site was one of the largest known occupations in the Levant for some millennia (ca. 14,300 - 11,900 cal BP). Remains of Natufian architecture were found, together with evidence of early experimenting with pyrotechnology for the creation of lime plaster. Several features were identified during the excavations as assumed lime plaster installations. Samples investigated by micromorphology methods under the polarizing microscope revealed that while all were composed of calcium carbonate, and some indeed represent anthropogenic burnt lime products, others reflected the results of post-depositional or contemporaneous natural processes rather than technological products. The study of the samples at a molecular level through Raman spectroscopy enables a new methodology for the quick distinction between the features observed by micromorphology

A new approach to switch fabrics based on mini-router grids and output queueing

A number of switch fabric architectures based on mini-router grids (MRG) have been proposed as a replacement of buses for system-on-chip communication, as well as a replacement of crossbars for network routers. The rationale for using MRGs in switch fabrics is that they provide high delivery ratios, low latencies, high degree of parallelism and pipelining, load balancing properties, and sub-quadratic cost growth for their implementation. The traditional approaches to switch fabrics are based on input queuing (IQ) or virtual output queueing (VOQ), because output queuing (OQ) solutions to date are unscalable and expensive due to the speedup problem. However, we show that the speedup problem introduced by OQ can be bounded by 3 by using MRGs.We present the design of a switch fabric based on OQ MRGs that offers high delivery ratios, smaller queue sizes, and QoS guarantees. Queueing and scheduling are distributed over the MRs, where each MR is a pipestage, thus allowing MRGs to provide high throughput by nature. We present the first in-depth analytical model of switch fabric architectures based on OQ MRG, and support our model with register-transfer level (RTL) simulations in SystemC. The analytical and simulation results are shown to have close correlation over a range of design parameters and evaluation metrics