Micro-PIXE study of gold archaeological objects

Several fragments of ancient gold objects coming from an Eneolithic hoard and from Pietroasa Cloca cu Puii de Aur (The Golden Brood Hen with Its Chickens) hoard, unearthed on Romanian territory, and two Romanian native gold nuggets samples were analyzed using micro-PIXE technique. The purpose of the study was to clarify the metal provenance. Trace and minor elements (Cu, Te, Sn, Pb, Ti, Cr, V, Mn, Ta) and platinum group elements (PGE) concentrations were estimated. The presence of inclusions (micrometer size areas of composition different from the surroundings) was investigated. We found Si and Ca inclusions on two Eneolithic samples, and Ta inclusions on two samples from Pietroasa hoard. The measurements suggested an alluvial origin of gold for the Eneolithic samples and give indications for the possible gold ore sources of Pietroasa hoard.     

Spatially resolved mass spectrometry in the study of art and archaeological objects

Spatially resolved mass spectrometry (MS) is a widespread technique increasingly used in many areas of research. Operating in a fast, straightforward way with minimal sample damage, MS investigation can provide spatially resolved information with low limits of detection and a wide linear range. For these reasons, spatially resolved MS is applied in the study of art and archaeological objects, and the current review provides a survey of relevant publications. We highlight the main capabilities and the limitations of spatially resolved MS and discuss the most relevant applications.     

The k 0 and relative INAA methods to determine elements in entire archaeological pottery objects

The advantages of instrumental neutron activation analysis applied to archaeological ceramics have been enhanced through the analysis of entire objects, using both the k ₀ method and the relative method, respectively, to determine the concentrations of chemical elements in aliquots of replicate objects used as comparators and in the sample object. Twenty-two chemical elements of archaeological importance were measured in mud figurines from Caral civilization (5000 year BC), irradiated inside a well-characterized radial channel facility of the nuclear research reactor at IPEN, Peru. The results showed less than 10 % of bias for most of the elements.     

Application of radiation chemistry for conservation of archaeological waterlogged wood and osteological objects

The application of radiation chemistry to the conservation of archaeological objects is described. Methyl methacrylate is introduced into the voids of the objects to be conserved either by an exchange process or—if allowed by the mechanical strength of the object—by vacuum impregnation. It is neither necessary nor desirable to fill the object completely with the monomer that is subsequently polymerized with ⁶⁰Co γ-rays.     

Insights into electrolytic stabilization with weak polarization as treatment for archaeological copper objects

Immersion of corroded copper artefacts in dilute sodium sesquicarbonate solution is a well-recognized stabilization technique—especially in the conservation of objects recovered from marine environments and therefore saturated with chlorides. Here we describe three linked experiments performed to investigate a variation on this treatment, involving the application of a low potential to the artefact in order to drive the chloride extraction process. This includes a new spectroelectrochemical approach which allows 2-D pseudorandom X-ray reflection diffraction patterns to be obtained without interrupting the reaction in solution. Experiments were carried out on synthetically produced chloride layers on copper (nantokite and atacamite). We show that a thick chloride layer is, in general, replaced by a thin cuprite layer through a mechanism which involves detachment of the chloride crystallites from the surface prior to dissolution.     

Semilocalized approach to investigation of chemical reactivity

Application of the power series for the one‐electron density matrix 36 to the case of two interacting molecules is shown to yield a semilocalized approach to investigate chemical reactivity, which is characterized by the following distinctive features: (1) Electron density (ED) redistributions embracing orbitals of the reaction centers of both molecules and of their neighboring fragments are studied instead of the total intermolecular interaction energy; (2) the ED redistributions are expressed directly in the basis of fragmental orbitals (FOs) without passing to the basis of delocalized molecular orbitals (MOs) of initial molecules; (3) terms describing the ED redistributions due to an intermolecular contact arise as additive corrections to the purely monomolecular terms and thereby may be analyzed independently; (4) local ED redistributions only between orbitals of the reaction centers of both molecules are described by lower‐order terms of the power series, whereas those embracing both the reaction centers and their neighborhoods are represented by higher‐order terms. As opposed to the standard perturbative methods based on invoking the delocalized (canonical) MOs of isolated molecules, the results of the approach suggested are in‐line with the well‐known intuition‐based concepts of the classic chemistry concerning reactivity, namely, with the assumption about different roles of the reaction center and of its neighborhood in a chemical process, with the expectation about extinction of the indirect influence of a certain fragment (substituent) when its distance from the reaction center grows, etc. Such a parallelism yields quantum chemical analogs for the classic concepts and thereby gives an additional insight into their nature. The scope of validity of these concepts also is discussed. Applicability of the approach suggested to specific chemical problems is illustrated by a brief consideration of the S_N2 and Ad_E2 reactions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 302–316, 2003     

A multi-analytical approach for the characterization of powders from the Pompeii archaeological site

Nine black powders found in Pompeii houses in three different types of bronze vessels (cylindrical theca atramentaria, unguentaries, and aryballoi) were characterized in order to assess a correspondence between the composition and the type of vessel and, possibly, to verify if these powders were inks or not. For the compositional characterization, a multi-analytical approach was adopted, which involved the use of scanning electron microscopy-energy dispersive X-ray, Fourier-transformed infrared spectroscopy, Raman, X-ray diffraction, electron paramagnetic resonance spectroscopy, thermogravimetric analysis, gas chromatography coupled with mass spectrometry (GC/MS), and pyrolysis GC/MS. Powders contained in cylindrical theca atramentaria form a homogeneous group, and their organic and inorganic compositions suggest that they were writing inks, while powders contained in unguentaries and aryballoi could have had several different uses, including writing inks and cosmetics. Furthermore, the composition profile of the powders found in cylindrical cases shows that, at 79?AD: , in Pompeii, carbon-based inks were still used for writing, and iron gall inks had not been introduced yet.     

An approach to the atomic structure of bulk metallic overlayers using tip-induced layer-by-layer dissolution

Well-grown 3-D copper clusters were obtained on a Pt(111) surface at intermediate overpotentials from a sulfuric acid solution. The hexagonal and triangular clusters grew layer-by-layer and were aligned to the orientation of the substrate, indicating epitaxial growth without rotation. By using the tip as an anodic electrode, the atomic structure of each layer of the cluster was monitored locally during dissolution. The results show that in the copper clusters the lattice constant relaxes directly to the bulk lattice constant in the second layer (at least after deposition of the third layer). Additional discussion on the dissolution kinetics is also included. The same method has been used to elucidate the structure of the Cu overlayer on Pt(100).     

An investigation of the di-Grignard approach to metallabenzocyclobutenes of group 14

The reactions of 1,2-dihydro-1-magnesabenzocyclobutene (5) with dichlorodimethylsilane (12a), dichlorodimethylgermane (12b) and dichlorodimethylstannane (12c) are reported; 1,2-dihydro-1,1,dimethyl-1-silabenzocyclobutene (14a) and 1,2-dihydro-1,1-dimethyl-1-germabenzocyclobutene (14b) were formed in high yields, but the tin analogue 14c was not obtained. Eight-membered ring species, the dimers 17 and 18, were isolated for all three metals. Other products gave useful indications of the probable course of these interesting and complex reactions.     

Development of a micro-X-ray fluorescence system based on polycapillary X-ray optics for non-destructive analysis of archaeological objects

A new micro-X-ray fluorescence (micro-XRF) system based on rotating anode X-ray generator and polycapillary X-ray optics has been set up in XOL Lab, BNU, China, in order to be used for analysis of archaeological objects. The polycapillary X-ray optics used here can focus the primary X-ray beam down to tens of micrometers in diameter that allows for non-destructive and local analysis of sub-mm samples with minor/trace level sensitivity. The analytical characteristics and potential of this micro-XRF system in archaeological research are discussed. Some described uses of this instrument include studying Chinese ancient porcelain.     

A new approach to the calorimetric investigation of physical and chemical transitions

The theoretical basis for Modulated DSC is described and the additional information in can give over conventional DSC illustrated for some polymers.     

Study of archaeological ceramics by total-reflection X-ray fluorescence spectrometry: Semi-quantitative approach

Total-reflection X-ray fluorescence spectrometry has been compared with Instrumental Neutron Activation Analysis in order to test its potential application to the study of archaeological ceramics in the archaeometric field. Two direct solid non-chemical sample preparation procedures have been checked: solid sedimentation and solid chemical homogenization. For sedimentation procedure, total-reflection X-ray fluorescence allows the analysis of the elemental composition with respect to the size fraction but not the average evaluation of the composition. For solid chemical homogenization procedure, total-reflection X-ray fluorescence provides precise (from 0.8% to 27% of coefficient of variation) and accurate results (from 91% to 110% of recovery) for 15 elements (Cr, Hf, Ni, Rb, Al, Ba, Ca, K, Mn, Ti, V, Cu, Ga, Y and Fe) with an easy sample preparation process of the solid clay and without previous chemical treatment. The influence of the particle sizes has been checked by total-reflection X-ray fluorescence sample angle scans and anomalous behaviors have been found for three additional detected elements: As, Sr and Zn, which can be attributed to interference effects of the mineral grain sizes of their associated chemical phases in the total-reflection X-ray fluorescence interference region. The solid chemical homogenization procedure produces data useful for archaeological interpretation, which is briefly illustrated by a case-study. Finally, the decantation procedure data can be also useful for size chemical speciation and, consequently, for alternative environmental total-reflection X-ray fluorescence applications.     

ArtTAX - a new mobile spectrometer for energy-dispersive micro X-ray fluorescence spectrometry on art and archaeological objects

A newly developed spectrometer for energy-dispersive micro X-ray fluorescence spectrometry has been designed for the demands of archaeometry. ArtTAX combines the advantages of non-destructive and sensitive multi-elemental analysis at sub-mm resolution with the possibility of working outside the laboratory. The spectrometer consists of an air-cooled, low-power molybdenum tube, new generation polycapillary X-ray optics, a silicon drift detector without the need for liquid-nitrogen cooling, a CCD camera, and three light diodes for sample positioning. The motor-driven measurement head is fixed on a x,y,z-flexible tripod support which can be assembled and dismantled within minutes. The spot size of the primary X-ray beam was determined to be 94 microm for the Cu(Kalpha) energy, the detection limits are in a range of a few tens of microg g(-1) for the medium energy-range in glass. Additional open helium purging in the excitation and detection paths enables the determination of elements down to sodium, thus avoiding vacuum conditions or a size-limiting sample chamber. A selection of qualitative and quantitative results on pigment, metal, glass, and enamel analyses are presented to show the potential of ArtTAX in the field of art and archaeology.     

Mathematical approach to investigation of synthesis processes at high temperatures

In our work, we present a method for estimation of the diffusion and reaction rates of synthesis at high temperatures using limited information from laboratory experiments, such as synthesis time and dimensions of reactants. Synthesis by sol-gel and solid-state reactions is considered. The inverse modeling problem is solved for one- and two-dimensional models. Explicit formulas for the diffusion coefficient and reaction rate as functions of temperature are obtained. The activation energies are calculated, and the lower bounds of diffusion and reaction rates are estimated, thus obtaining conditions for occurrence of synthesis.      

Surface-enhanced spectroscopic investigation of the adsorption properties of hydroxybenzoic acid isomers onto metallic surfaces

Surface-enhanced Raman Spectroscopy (SERS), surface-enhanced infrared absorption spectroscopy (SEIRA), temperature-programmed desorption (TPD), and density functional theory were used to characterize the adsorption properties of the hydroxybenzoic acid (HBA) isomers including ortho-hydroxybenzoic acid (OHA), meta-hydroxybenzoic acid (MHA), and para-hydroxybenzoic acid (PHA) using various deposition solvents with different polar properties. SERS typically enhances the Raman shifts of the monolayer, while SEIRA is a longer range effect, often providing vibrational enhancement to both the monolayer and multilayer. TPD analysis showed that OHA adsorption to silver is weaker than MHA/PHA, most likely as a result of the strong OHA intramolecular hydrogen-bonding. SERS and SEIRA demonstrated that OHA ionized efficiently in the monolayer and multilayer independent of the solvent polarity because of OHA's low pK_a (2.98). MHA/PHA ionized better than OHA in the multilayer in less polar deposition solvents, and a decrease in the polarity of the deposition solvent created additional ordering in the MHA monolayer while inducing stronger adsorption in the PHA monolayer. It is believed that a lower level of solvation with less polar deposition solvents allowed for more adsorbate/substrate interaction and more intermolecular attraction. The addition of more MHA to a multilayer resulted only in stronger SEIRA peaks. As a PHA multilayer thickened there was significant structural changes represented by new bands and spectral peak shifts with greater intermolecular attraction as the multilayer approached bulk properties. Due to the range of applications involving HBA isomers, these studies could find significant applications in biochemistry, medicine, nanotechnology and environmental science.     

A meshless approach for electromagnetic simulation of metallic carbon nanotubes

In this paper, a study on the electromagnetic behaviour of a single wall carbon nanotube model is described. The electrons available for conduction are treated as a thin cylindrical layer fluid and their motion is described by means of classical hydrodynamics equations in linearized form. These equations are solved in time domain using the Smoothed Particle Hydrodynamics method. The method suitably handled runs on GRID environment.     

Application of thermomagnetometry to corrosion studies of archaeological iron

Summary Thermomagnetometry has been applied to mineralized archaeological iron samples and samples from accelerated corrosion tests. It has successfully quantified the degree of corrosion, measured by the loss of iron, as well as the amount of magnetite formed and water held in the corrosion and adhered soil layers. Thermomagnetometry, thermogravimetric analysis and differential scanning calorimetry have been applied to the reported corrosion products from archaeological iron. Fourier transform infra-red and Raman spectroscopies and X-ray diffraction analyses were undertaken on the residues and at intermediate heating stages, where the thermal analyses indicated, to identify the reaction products.     

Scientific methods applied to the study of art objects

Scientific methods applied to the study of works of art are varied (examination, analysis and dating) and must be chosen with care in accordance with the object of the research. This paper briefly sets out the state of the art highlighting the development and applications of non-destructive methods. Such methods come under either the use of electromagnetic or particle radiation for the formation of images based on shape, development technique, or, on the other hand, the quantitative determination of elements down to and including their traces, isotopes or microsurfaces for the purpose of identifying the matter, its date, origin and development.