Technological features of ‘gnathia’ pottery

‘Gnathia’ pottery samples, dating back to the mid‐fourth and third century BC, from the archaeological site of Egnazia (Fasano, Brindisi, Italy) have been characterised from the physical‐chemical, mineralogical and morphological points of view. Optical and scanning electron microscopy, X‐ray energy‐dispersive spectroscopy and X‐ray diffraction analyses have been carried out on the ceramic body, black gloss, white, yellow and red over‐paintings of fragments, with the aim of outlining technological features and defining the nature of coatings and decorations. Analytical results confirm from both a technological and morphological/decorative point of view the close relationship between ‘Gnathia’ pottery and red figured pottery, particularly with the Apulian red figured from which it takes its inspiration. At the same time the experimental results highlight shared characteristics and differences with both Attic and Apulian red figured productions. The biggest difference is in the utilisation of the ‘ingobbio rosso’ layer that covers the ceramic body. This does not seem to be based on aesthetic grounds, as in the case of Apulian red figured pottery, but on application of acquired production processes, since ‘Gnathia’ pottery was made in the same workshops as red figured pottery. Copyright © 2009 John Wiley & Sons, Ltd.     

Joaquin Sorolla's pigment characterisation of the paintings ‘Vision of Spain’ by means of EDXRF portable system

In this work, portable energy dispersive X‐ray fluorescence (EDXRF) spectrometry was employed to the characterisation of the palette used by the Spanish artist Joaquín Sorolla (1863–1923) in the paintings ‘Vision of Spain’, a set of 14 oils on canvas painted by Sorolla between 1911 and 1919 by order of Mr Archer Huntington to decorate the library of the Hispanic Society of America (HSA) in New York. The analyses, sponsored by BANCAJA and provided by the HSA, were carried out in situ, prior to the cleaning and restoration process, while the paintings hanging on the walls of the library of the HSA. The results revealed that the paintings were made over different priming layers containing, respectively, lead white, zinc and barium compounds, lead white mixed with zinc white or lead white mixed with zinc and barium compounds. The EDXRF analyses of coloured zones identified up to 29 inorganic pigments and, in some cases, the probable use of organic pigments. Sorolla used traditional pigments as earth pigments, lead white, vermillion, etc., and modern pigments as cadmium yellow, zinc white, cobalt‐based blue, chromium‐based green, manganese‐based violet, etc. These results provide valuable information about the Sorolla's palette during the last stage of his life. Copyright © 2011 John Wiley & Sons, Ltd.     

Einstein's ‘Zürich Notebook’ and his journey to general relativity

On the basis of his ‘Zürich Notebook’ I shall describe a particularly fruitful phase in Einstein's struggle on the way to general relativity. These research notes are an extremely illuminating source for understanding Einstein's main physical arguments and conceptual difficulties that delayed his discovery of general relativity by about three years. Together with the ‘Entwurf’ theory in collaboration with Marcel Grossmann, these notes also show that the final theory was missed late in 1912 within a hair's breadth. The Einstein‐Grossmann theory, published almost exactly hundred years ago, contains, however, virtually all essential elements of Einstein's definite gravitation theory.     

Traffic flow models with ‘slow-to-start’ rules

We investigate two models for traffic flow with modified acceleration (‘slow-to-start’) rules. Even in the simplest case v_max = 1 these rules break the ‘particle-hole’ symmetry of the model. We determine the fundamental diagram (flow-density relationship) using the so-called car-oriented mean-field approach (COMF) which yields the exact solution of the basic model with v_max = 1. Here we find that this is no longer true for the models with modified acceleration rules, but the results are still in good agreement with simulations. We also compare the effects of the two different slow-to-start rules and discuss their relevance for real traffic. In addition, in one of these models we find a new phase transition to a completely jammed state.     

‘Locking and unlocking control’ of photochromism of naphthopyran derivative

A ‘locking and unlocking control’ for a photochromic molecular system has been developed by using a photochromic naphthopyran derivative 1a as the model compound. With UV light irradiation, the colorless solution of 1a underwent ring‐opening photoisomerization and converted to a purple solution 1b , which quickly faded back to a colorless solution with visible light (λ ≥ 480 nm) irradiation or in the dark. Addition of boron trifluoride diethyl etherate to the solution of 1b produced a complex compound 2b , accompanying the color change from purple to blue. It was found that 2b remained photochemically inactive. With the addition of diethanolamine, however, the ‘locked’ photoreaction of 2b could be unlocked and converted back to 1b , in which the photochromism was recovered. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman imaging and stress quantification in self‐assembled graphene oxide fiber ‘Latin Letters’

To probe the intrinsic stress distribution in terms of spatial Raman shift (ω) and change in the phonon linewidth (Γ), here we analyze self‐assembled graphene oxide fibers (GOF) ‘Latin letters’ by confocal Raman spectroscopy. The self‐assembly of GOF ‘Latin letters’ has been explained through surface tension, π–π stacking, van der Waals interaction at the air–water interface and by systematic time‐dependent investigation using field emission scanning electron microscopy analysis. Intrinsic residual stress due to structural joints and bending is playing a distinct role affecting the E_2g mode (G band) at and away from the physical interface of GOF segments with broadening of phonon linewidth, indicating prominent phonon softening. Linescan across an interface of the GOF ‘letters’ reveals Raman shift to lower wavenumber in all cases but more so in ‘Z’ fiber exhibiting a broader region. Furthermore, intrinsic stress homogeneity is observed for ‘G’ fiber distributed throughout its curvature with negligible shift corresponding to E_2g mode vibration. This article demonstrates the significance of morphology in stress distribution across the self‐assembled and ‘smart‐integrable’ GOF ‘Latin letters’. Copyright © 2016 John Wiley & Sons, Ltd.     

Enhanced gauge symmetry from ‘toric’ G2 cones

We discuss the construction of M‐theory compactifications on ‘toric’ G₂ cones, a class of models which generalize those recently considered by Acharya and Witten. We explain our criteria for identifying the gauge group content of such theories and briefly discuss the associated metrics.     

Spectroscopic investigation of modern pigments on purportedly medieval miniatures by the ‘Spanish Forger’

Five miniatures by the so‐called ‘Spanish Forger’ were acquired by the Victoria and Albert Museum in 2008. Believed to be authentic medieval miniatures until the mid‐twentieth century, they are now considered to have been painted around the end of the nineteenth and the beginning of the twentieth century. To investigate this attribution and to gather detailed knowledge about the materials used by the artist, a comprehensive pigment analysis by Raman microscopy and X‐ray fluorescence was carried out. Although traditional materials such as vermilion, carbon black, red lead, lead white and indigo were identified, many others (chrome yellow, Scheele's green, emerald green and ultramarine blue) are modern and synthetic pigments, a result which provides a firm scientific basis for stating that the miniatures are forgeries. Copyright © 2009 John Wiley & Sons, Ltd.     

Calibration of the MER α‐particle x‐ray spectrometer for detection of ‘invisible’ OH and H2O possibly present in Martian rocks and soils

An existing Monte Carlo code was modified and extended to predict the intensity ratio of elastically and inelastically scattered plutonium Lα x‐rays incident on rock samples in the Mars Exploration Rover's α‐particle x‐ray spectrometer (APXS) device. The systematics of the scatter ratio as a function of effective sample atomic number are explored. The simulated Rayleigh/Compton ratios (R/C)_sim are compared with measured ratios (R/C)_meas that are obtained by fitting APXS spectra of geochemical reference materials using an x‐ray fluorescence version of GUPIX. The quantity K = (R/C)_meas/(R/C)_sim is then plotted against the mean atomic number of the sample to provide a calibration for known samples. Departures of K values of unknown samples from this calibration may then be attributed to the presence of light, ‘invisible’ elements in the sample. This work is part of an ongoing project aimed at developing methods to quantify bound water in Martian rocks analyzed by the present and the next generation APXS instruments. Copyright © 2006 John Wiley & Sons, Ltd.     

Study of the ‘Raman spectroscopic signature of life’ in mitochondria isolated from budding yeast

The ‘Raman spectroscopic signature of life’ is a Raman band at 1602 cm⁻¹ that sharply reflects the metabolic activity of cell mitochondria. Here we report the study of thissignature in isolated yeast mitochondria. The existence and behaviour of the 1602 cm⁻¹ band in isolated mitochondria have been confirmed to be the same as in living yeast cells: the intensity of the band decreases with timewhen a respiration inhibitor, sodium azide, is added. The present study shows the significance of isolated mitochondria in elucidating the origin of this still unassigned Raman band. Copyright © 2009 John Wiley & Sons, Ltd.     

Routine x‐ray fluorescence analysis of powder materials using the ‘VERBA‐XRF’ mode

A new version of the ‘VERBA‐XRF’ mode was developed for the determination of the contents of principal elements with atomic numbers Z > 10 and SUM9, that is, the sum of the contents of complementary elements with Z < 9 in powder materials without alloying with borax. An original set of equations provides determination of the SUM9. Analysis was made on 120 samples: dust from electric filters, clay, clinker, gypsum, bauxite, slag, candle‐end, shale, schlamm and chalk. The results obtained in the determination of the elements Fe, Ti, Ca, K, S, Si, Al and Mg have relative standard errors of 1–2%. The availability of the value of the SUM9 provided the possibility of determining chemical compositions in samples. The content of mineral white in natural gypsum was calculated. Copyright © 2004 John Wiley & Sons, Ltd.     

Nondestructive elemental depth profiling of Japanese lacquerware ‘Tamamushi‐nuri’ by confocal 3D‐XRF analysis in comparison with micro GE‐XRF

We have applied recently two XRF (micro x‐ray fluorescence) methods [micro‐Grazing Exit XRF (GE‐XRF) and confocal 3D‐XRF] to Japanese lacquerware ‘Tamamushi‐nuri.’ A laboratory grazing‐exit XRF (GE‐XRF) instrument was developed in combination with a micro‐XRF setup. A micro x‐ray beam was produced by a single capillary and a pinhole aperture. Elemental x‐ray images (2D images) obtained at different analyzing depths by micro GE‐XRF have been reported. However, it was difficult to directly obtain depth‐selective x‐ray spectra and 2D images. A 3D XRF instrument using two independent polycapillary x‐ray lenses and two x‐ray sources (Cr and Mo targets) was also applied to the same sample. 2D XRF images of a Japanese lacquerware showed specific distributions of elements at the different depths, indicating that ‘Tamamushi‐nuri’ lacquerware has a layered structure. The merits and disadvantages of both the micro GE‐XRF and confocal micro XRF methods are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Adaptivity and ‘Per learning’

One of the key points addressed by Per Bak in his models of brain function was that biological neural systems must be able not just to learn, but also to adapt—to quickly change their behaviour in response to a changing environment. I discuss this in the context of various simple learning rules and adaptive problems, centred around the Chialvo-Bak ‘minibrain’ model (Neurosci. 90 (1999) 1137).     

Raman and SEM‐EDX analyses of the ‘Royal Portal’ of Bordeaux Cathedral for the virtual restitution of the statuary polychromy

The chemical analysis of the remains of paintings from the Royal Portal of Bordeaux Cathedral was carried out by in situ analytical techniques and by laboratory techniques after sampling. Even though, nowadays, portable systems have a good performance and provide reliable results, in the present case, the in situ approach failed, and the analysis had to be carried out in the laboratory. The obtained results were used to propose a virtual restitution of the polychromy and to have an idea of how this portal was when it was built in the XIII century. During the analysis, the degradation process of pigment azurite was studied through the determined decay products, such as copper oxalate (moolooite) and copper basic sulfate (brochantite). This degradation seems to occur because of the presence of oxalic acid in the chemical system, as other calcium oxalates (weddellite) were identified as a degradation product of calcareous support. Copyright © 2015 John Wiley & Sons, Ltd.     

Comparison of ‘blue’ and ‘infrared’ emission bands in thermoluminescence of alkali feldspars

Dating quaternary sediments by thermoluminescence (TL) or optically stimulated luminescence (OSL) calls for a detailed knowledge of the luminescence of feldspars. TL of the various alkali feldspars ((K, Na) Si₃AlO₈) display many common features, and some of these cause great difficulties for dating. After long storage following ionizing irradiation, the TL of most alkali feldspars is known to fade away by “anomalous fading”, which is incompatible with dating. This effect had been attributed to tunnel recombination. Following irradiation, a very intense tunnelling afterglow is observed at temperatures down to liquid nitrogen, in accordance with the observed rate of fading. This emission has a Gaussian spectrum entirely in the infrared (IR) with a maximum at 1.7 eV. It displays an important thermal quenching from 77 to 300 K. Its intensity is related with the ‘disorder’ of the crystal lattice. At higher temperatures, in TL proper, two emission bands can be separated. One is the well-studied complex visible emission, distributed over the spectral region from UV to orange, but mostly ‘blue’. The other is the ‘infrared’ band already observed at lower temperatures, which is attributed to Fe³⁺ ions. These two bands are clearly separated, with the spectral maxima, respectively, below and above 600 nm. They have also different kinetics, the glow peaks temperatures are different. But these two different bands are also coupled in many ways, they have parallel growth and fading. With ‘disordered’ feldspars, the ‘blue’ emission displays anomalous fading, which is stronger than that of the ‘infrared’. The infrared emission is more stable, which may be interesting for the purpose of dating.     

Photorefractive half-adder: beam-fanning for optical generation of ‘SUM’ and ‘CARRY’

Optical implementation of an adder of arithmetic units that processes binary numbers is outlined. Dynamic range compression using biasing illumination in beam-fanning geometry as observed in a photorefractive BaTiO₃:Fe crystal forms the underlying principle of operation. By proper choice of polarization for two input signals, XOR and AND operations are realized. These two operations are essentially analogous to SUM and CARRY generation for binary addition. By providing shift (only in case of CARRY) and feedback, experimental results for half-adder are obtained. In addition, the technique forms a very simple way of implementing ‘original carries’ as required for full-adder. The geometry proposed is simple, energy-efficient and can be easily extended to multi-wavelength operations thus achieving spectral parallelism in optical domain.     

A stable ‘sandwich’ system of Surface‐Enhanced Resonance Raman Scattering for the analysis of β‐carotenes in a photosynthetic pigment‐protein complex

In plants, Photosystem I (PSI) is composed of a core complex and a membrane‐associated antenna complex light‐harvesting complex I that captures light and funnels its energy to the core complex. To obtain Raman structural information on β‐carotenes embedded in the PSI core complex, a ‘sandwich’ system of roughened silver slice: target protein complexes: single silver nanoparticles was fabricated for Surface‐Enhanced Resonance Raman Scattering (SERRS) measurements. This study provided a method to overcome spectral irreproducibility, which is the main drawback of Surface‐Enhanced Raman Scattering/SERRS‐based studies. The Raman spectra of β‐carotenes embedded in the PSI core complex can be obtained at very low sample concentrations (1–5 µg Chl/ml) and high signal/noise ratios. The β‐carotenes in the spinach PSI core complex were predominantly all‐trans configuration. The membrane protein‐mediated adsorption of silver nanoparticles induced the uniform distribution of a large number of single nanoparticles, which contributed to achieving highly reproducible SERRS spectra. This study is the first to apply single silver nanoparticle‐based SERRS analysis in membrane proteins. Copyright © 2013 John Wiley & Sons, Ltd.     

Micro‐Raman spectroscopy analysis of 16th century Portuguese Ferreirim Masters oil paintings

In the present work a set of eight altarpieces of the 16th century (1532–1534), attributed to the Ferreirim Masters (Gregório Lopes, Garcia Fernandes and Cristóvão de Figueiredo), from the Santo António de Ferreirim Monastery (North of Portugal), were analysed by micro‐Raman spectroscopy. For this purpose some samples were taken from the paintings to characterise its artist's ‘school’. It was found that the preparation was made with chalk and gypsum and the palette composed mainly of lamp black, azurite, lead white (mixed with other pigments), lead–tin yellow type I, goethite (the main constituent of yellow ochre), red lead (as under painting), haematite (the main constituent of red ochre) and vermilion. Indigo was detected in one sample. Some derivatives and degradation products were found mainly in the panels subjected to high temperatures during a fire occurred in 1954: a degradation product from massicot or red lead, lead carbonate (dehydrated derivative of lead white), bassanite and anhydrite (hemi‐ and dehydrated forms of gypsum). These results are compared with those of previous total reflection X‐ray fluorescence spectroscopy (TXRF) analyses. Copyright © 2009 John Wiley & Sons, Ltd.     

Non‐destructive, ‘in situ’, characterization of pigments in Minoan pottery at the stratigrafical museum of Phaistos (Crete)

This paper presents preliminary results of measurements of chemical composition of pigments on the Middle Minoan pottery coming from Festos and Hagia Triada excavations. The measurements were carried out ‘in situ’ with the use of the PIXE‐alpha spectrometer, with Po‐210 radioisotope as a source of sample excitation, built at Laboratorio Nazionale del Sud. The method of measurements is described in detail and the limits are discussed. The preliminary results confirm the use of the reduced iron technique to obtain the black slips and of the talc to produce the white ones. Similarly, the presence of Manganese in some orange pigments can be associated with the use of red ochre mixed to talc, the latter being used as whitening material. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of the spectacular gold and silver from the Moche tomb ‘Señora de Cao’

On the north coast of present‐day Peru, between the Andes and the Pacific Ocean, approximately between 100 and 600 ad , the Moche civilization prospered. The Moche were very sophisticated artisans and metal smiths, so that they are considered the finest producers of jewels and artifacts of the region. Their metalworking ability was impressively demonstrated by the excavations of the tomb of the ‘Lady of Cao’ (dated around third–fourth century ad ) discovered by Regulo Franco in 2005. Impressive is the beauty of the artifacts, and also the variety of metallurgical solutions, demonstrated by not only the presence of objects composed of gold and silver alloys but also of gilded copper, gilded silver, and tumbaga, a poor gold Cu‐Au alloy subject to depletion gilding. About 100 metal artifacts from the tomb of the Lady of Cao, never before analyzed, were studied by using various portable equipments based on following non‐destructive and non‐invasive methods:

• energy‐dispersive X‐ray fluorescence with completely portable equipments;
• transmission of monenergetic X‐rays;
• radiographic techniques; and
• optical microscopy.

Gold objects and gold areas of nose decorations are characterized by approximately the same composition, that is, Au = (79.5 ± 2.5) %, Ag = (16 ± 3) %, and Cu = (4.5 ± 1.5) %, while silver objects and silver areas of the same nose decorations show completely erratic results, and a systematic high gold concentration. Many gilded copper and tumbaga artifacts were identified and analyzed. Further, soldering gold–silver was specifically studied by radiographs. Additional measurements are needed, particularly because of the suspect that depletion gilding was systematically employed also in the case of some nose decorations. Copyright © 2016 John Wiley & Sons, Ltd.