THE PRE-DOSE TECHNIQUE: A NEW THERMO-LUMINESCENT DATING METHOD

A thermoluminescent (TL) glow-curve peak occurs around 110°C for the mineral quartz. Its sensitivity may be changed by application of a radiation dose (termed the pre-dose) followed by a heating of the quartz to 500°C: heating alone causes no sensitivity change. The enhancement observed (measured relative to the sensitivity of the peak prior to heating) is a measure of the magnitude of the pre-dose. For quartz extracted from pottery the sensitivity enhancement induced by laboratory heating records a natural pre-dose, i.e. the accumulated dose experienced during archaeological burial. The latter quantity is used in TL age-determination and a test programme is reported on the application of the pre-dose dating method to sites covering the Roman era in Britain forward to modern times.     

Field gamma spectrometry,Monte Carlo simulations and potential of non-invasive measurements

The determination of gamma dose rates is of prior importance in the field of luminescence dating methods. In situ measurements are usually performed by the insertion of dosimeters or a portable gamma spectrometer cell in sediments. In this paper, Monte-Carlo simulations using the Geant4 toolkit allow the development of a new technique of insitu gamma dose rate evaluations: a spectrometer cell is placed on the surface of sediments under excavation to acquire successive spectra as sediments are removed by excavations. The principle of this non-invasive technique is outlined and its potential is discussed, especially in the case of environments in which radioelements are heterogeneously distributed. For such cases, a simple method to reconstruct gamma dose rate values with surface measurements using an attenuator is discussed, and an estimation of errors is given for two simple cases. This technique appears to be applicable, but still needs experimental validation.     

Distribution in SAR palaeodoses due to spatial heterogeniety of natural beta dose

In luminescence dating of sediments, Mayya et al. (2006) pointed out that at single grain level, the beta dose for quartz grains is heterogeneous. This heterogeneity arises due the fact that the total potassium in sediment is contributed by few feldspar grains with up to 11–14% stoichiometric potassium (Huntley and Baril, 1997). Beta particles have a range of ∼2 mm, which is comparable to grain sizes and inter-grain distances. This fact implies that the spatial fluctuation of beta emitters (K-feldspars) around individual quartz grains results in heterogeneous dose deposition. These fluctuations therefore, lead to an inherent spread in palaeodoses received by individual quartz grains.     

Expectations of scatter in equivalent-dose distributions when using multi-grain aliquots for OSL dating

In the OSL dating of sediment, the scatter in equivalent dose (D _e) between grains is almost always larger than would be expected due to counting statistics alone. Some scatter may be caused by insufficient (partial) bleaching of some of the grains prior to deposition. In order to date partially bleached sediment, it is essential to estimate the amount of scatter caused by other processes (e.g. grain-to-grain variability in the natural dose rate). Measurements of such scatter are performed at the single-grain level; by contrast, most OSL dating is performed on multi-grain subsamples, for which grain-to-grain scatter is reduced through averaging.     

Roman traces in Germania magna: New thermoluminescence and pIRIR290 data from a lime kiln at Bergisch Gladbach,Germany

The applicability of a post‐infrared infrared stimulated luminescence (pIRIR₂₉₀) protocol and two different thermoluminescence (TL) protocols—a single aliquot regeneration (SAR) and a multiple aliquot additive dose (MAAD)—was tested on six polymineral fine‐grain (4–11 μm) samples extracted from the wall remains of a Roman lime kiln and a Roman roof tile. These remains had been excavated close to Bergisch Gladbach, which was at that time part of Germania magna. For the pIRIR₂₉₀ measurements, no dependence of D_e on first‐stimulation temperature was detectable, and the standard first stimulation temperature at 50°C was adopted. Fading tests and dose‐recovery tests were made for all samples. Background subtracted glow curves were recorded up to 480°C for TL after a preheat of 220°C for 120 s. A‐values were determined for all TL and pIRIR measurements. The results for all three protocols were fairly consistent, and TL and pIRIR₂₉₀ protocols are shown to be suitable to estimate reliable equivalent doses for the fired kiln walls. The resulting ages are in agreement with the expected time range—Roman Iron Age—and with independent age control provided by radiocarbon ages of animal bones and charcoal from the firing chamber.     

Gaining in impacts by leveraging the policy mix: Evidence from the European Cohesion Policy in more developed regions

This paper investigates how the overall impact of the European Cohesion Policy depends on the composition of the regional investment in Hard (infrastructure) and Soft (business and technical support) projects. The study employs a generalized propensity score (GPS) analysis in a multidimensional treatment context. In particular, the two dimensions considered are given by the Hard and Soft investments. The GPS estimation is based on a set of relevant idiosyncratic features of the regions. The second step estimates a dose–response function in a two-dimensional setting. The results confirm the existence of nonlinearities in the effect of different amounts of funds, but more importantly, show a degree of complementarity between Hard and Soft investment and that for policymakers, it is crucial to exploit such features to achieve more significant impact. The EU's more developed regions could have achieved a doubled GDP p.c. growth rate by pursuing a policy mix where Hard investments are reduced in favor of Soft investments. This improvement is comparable to the one obtained by at least doubling the available resources. The findings add to the evidence collected on the impact of the Cohesion Policy, suggesting a shift of the debate from the quantity to the quality of the expenditure pursued under the umbrella of territorial policies.     

LUMINESCENCE DATING OF SEDIMENTS—THE DETECTION OF HIGH EQUIVALENT DOSE GRAINS USING AN IMAGING PHOTON DETECTOR*

In this paper we describe quantitative measurements on the thermoluminescence of many single grains, made with an imaging photon detector. In several of the sediments examined a few bright grains were found which had a high equivalent dose (ED). Physical measurements made on these grains using binocular microscopy and analytical scanning microscopy enabled several possible explanations for the causes of the high ED grains to be rejected. Insufficient bleaching at deposition or the intrusion of grains from an older sediment were identified as the most probable explanation for these grains.     

A NEW THERMOLUMINESCENCE DATING TECHNIQUE FOR HEATED FLINT*

A new thermoluminescence (TL) technique for determining the age of heated flint artefacts from archaeological sites is presented. It is a variant of the SAR protocol, which is usually used for OSL dating of sediment, but it is not based on a presumed model for fitting the dose–response curve. Dose recovery tests as well as comparisons with standard protocols show the accuracy of the new technique. It is found that the sensitivity of the thermoluminescence (TL) signal of flint in the orange–red waveband does not show severe changes due to the heating process while measuring the TL. This allows the application of a short SAR procedure, which requires only two dose points. The technique does not require as much instrument time as other SAR techniques, and thus is advantageous for dating very old samples. The major advantage of this new technique is the small amount of sample material required, which allows the dating of samples that are too small for standard TL dating techniques.     

COMPOSITIONAL INHOMOGENEITY OF SEDIMENTS AND ITS POTENTIAL EFFECTS ON DOSE RATE ESTIMATION FOR ELECTRON SPIN RESONANCE DATING OF TOOTH ENAMEL

We present results of particle size and radioactivity analyses of sediment samples collected from five sites with different burial environments. The uranium, thorium and potassium concentrations in the five sample sets are shown to vary with particle size. The potential effects of the observed size-dependent variations on electron spin resonance (ESR) dating of tooth enamel are assessed using two hypothetical models. Our results show that any bias to relatively fine fractions could result in a significant overestimation of the total environmental dose rate, leading to an underestimation of the calculated ESR age.     

NEUTRON ACTIVATION ANALYSIS OF SIXTEENTH- AND SEVENTEENTH-CENTURY EUROPEAN BLUE GLASS TRADE BEADS FROM THE EASTERN GREAT LAKES AREA OF NORTH AMERICA*

Sixteenth- and seventeenth-century European blue glass trade beads from aboriginal sites in the eastern Great Lakes area of North America have been analysed non-destructively using low neutron dose instrumental neutron activation analysis, so that the beads could be returned to their keepers. Dark blue (cobalt-coloured) beads are readily separable from turquoise (copper-coloured) beads. Differences in the chemistries of the turquoise blue beads appear to be useful in separating glass beads from the two centuries. Low calcium, sixteenth-century turquoise beads tend to distintegrate by a leaching of the alkali metals.     

Rock surface luminescence dating of prehistoric rock art from central Iberia

Rock art paintings are notoriously difficult to date numerically. Recently, luminescence dating has been shown to provide reliable rock surface burial ages in various archaeological settings. Here we use the cross-cutting relationship between a fallen rock and two paintings of the Iberian Levantine (older) and Schematic (younger) styles to constrain the age of the paintings by dating the rockfall event using rock surface luminescence dating. Infrared-stimulated luminescence (IRSL) signals as a function of depth into the buried face of the talus border indicate that the IRSL signal measured at 50°C (IR₅₀) was sufficiently reset to a depth of about 1.6 mm prior to burial. An uncorrected IR₅₀ age of 1.6 ± 0.2 ka was calculated for the rockfall event by dividing the surface equivalent dose (D_e) by the total dose rate. This age was corrected using both conventional and field-to-laboratory saturation approaches to yield indistinguishable ages of 2.7 ± 0.5 and 2.9 ± 0.3 ka, respectively. Since the panel with Schematic art was first available to the artist after the rockfall, we conclude the Schematic rock art at Villar del Humo is younger than ~2.9 ka. The Levantine rock art was painted on a panel constrained by the talus boulder before detachment, and so it is likely to be older than ~2.9 ka.     

ELECTRON SPIN RESONANCE ANALYSIS OF MARINE GASTROPODS FROM COASTAL ARCHAEOLOGICAL SITES IN SOUTHERN AFRICA

Shell samples of the marine gastropod Turbo sarmaticus have been examined to assess their potential for electron spin resonance (ESR) dating. The shells were found to be composed of aragonite. ESR analysis shows the presence of three radiation sensitive peaks. Equivalent dose (ED) values for two of the peaks have been determined for thirteen samples. When the two sets of ED values are plotted against each other, four distinct clusters are found that appear to represent four different age groups. The apparent age groups determined here are consistent with the stratigraphic record of the sites.     

Luminescence dating of young coastal deposits from New Zealand using feldspar

A new measurement protocol has been tested on K-feldspars from Whanganui Inlet and Parengarenga Harbour, New Zealand. A Single Aliquot Regenerative (SAR) dose protocol, using two successive infrared (IR) stimulations (post-IR IR SAR protocol) is setup for these young (<1000 years) coastal sediments. Significant anomalous fading (g _2days =7 %/decade) is observed using the conventional IR signal measured at 50°C. In contrast, the fading rate of the IR signal measured at elevated temperature (150°C) after the IR stimulation at 50°C (a post-IR IR signal) is not significant (g _2days ≤ 1 %/decade). Surprisingly low residual infrared stimulated luminescence (IRSL) signals were observed for a surface sample, suggesting that accurate ages as young as ∼50 years can be obtained for these recent deposits. IRSL ages ranging between 48±6 years and 1050±50 years are obtained from six samples, indicating that sediment accumulation has occurred at the two sites during the last millennia, despite a falling trend in relative sea-level in Whanganui Inlet and a stable relative sea-level at Parengarenga Harbour.     

TL DATING OF BURNT LITHICS FROM BLOMBOS CAVE (SOUTH AFRICA): FURTHER EVIDENCE FOR THE ANTIQUITY OF MODERN HUMAN BEHAVIOUR*

This paper presents the first TL dates for burnt quartzites and silcretes from the Still Bay layers of Blombos Cave (South Africa). These layers contained engraved ochres and marine shell beads that could be an early manifestation of symbolic and thus ‘modern’ behaviour by the Middle Stone Age humans. The procedure devised to calculate the ages is presented in detail, particularly with regard to internal microdosimetry, because the problems faced in estimating the dose rates require an approach different from the one usually used on flints and sediments. A mean age of 74 ± 5 ka was obtained for five burnt lithics unearthed in the BBC M1 member of the Still Bay layers. This result is in good agreement with both ESR dates on teeth and OSL dates on sediment, and demonstrates the great antiquity of the archaeological remains discovered at Blombos Cave.     

POSSIBLE CARBON-14 ENRICHMENT IN HIGH ALTITUDE WOOD

It has been suggested that utilization of the bristlecone pine calibration for ¹⁴C age correction can result in dates which are up to several hundred years too early in comparison with archaeological evidence. Among other possible causes in situ production of ¹⁴C due to the high altitude growth region of the bristlecone pine has been proposed to explain this effect. Although theoretical evaluation indicates that a significant amount of ¹⁴C could be produced by this mechanism, irradiation of bristlecone pine wood with a neutron dose equivalent to the calculated cosmic ray maximum received by a 6000-year-old tree did not produce any detectable effect. Other geochemical considerations related to the growth environment of these trees may offer a possible explanation for enhanced ¹⁴C levels. These inherent uncertainties in the ¹⁴C record of the bristlecone pine emphasize the need for an alternative source of tree-rings for comparative correlation with the ¹⁴C time-scale.     

ESR Dating of Micoquian Industry and Neanderthal Remains at K?lna Cave, Czech Republic

Electron spin resonance (ESR) and mass spectrometric U-series dating has been carried out on teeth recovered from K?lna cave during the excavations of 1961–76. Linear and early uptake (LU and EU) age estimates are similar due to low internal U content of the teeth. In general, ESR ages decrease upward in the section, but teeth from stone-rich (“lumpy”) layers give anomalously young ages, due to uneven dose-rate distribution. Elephant molars also give anomalously low ages, apparently due to self-absorption of gamma dose. Disregarding anomalous data, earliest appearance of Micoquian lithics and last occurrence ofDicerorhinus kirchbergensisin layer 9b is dated to 69±8 ka, which places them near the oxygen isotope stage (OIS) 5a/4 boundary. Neanderthal remains and the latest occurrence of Micoquian lithics in level 7a are dated to 50±5 ka, in good agreement with an uncalibrated radiocarbon date for this level of about 45 ka. The interstadial character of the fauna of this level also agrees with its date which places it in OIS 3. We also report that three stadial/interstadial cycles recognized in the lithological, faunal and palynological record of levels 9b through 7a at Kölna occurred during the timespan from about 70 to 50 ka.     

Platinum Complexes for the Treatment of Cancer

Abstract

Some platinum coordination complexes are active anticancer drugs in animal and man. This new class of chemotherapeutics was discovered during the course of investigation of the electric field effect on bacterial growth. The platinum electrodes electrolyzed during the experiment, releasing a platinum complex which caused complete cessation of cell division in the bacterial rods. With this filamentation assay system, we were able to identify the specific chemical as cis-dichlorodiammineplatinum(II), a complex known since 1848. The bacterial studies with many such complexes suggested to us the generalizations that charged platinum complexes were bacteriocidal, while the neutral platinum complexes induced filamentation and, in lysogenic bacteria, lysis. The neutral complexes have ignificant activity against transplantable, virally induced, and chemically induced cancers in animals. They are synergistic with almost every other anticancer drug in current use. In man kidney toxicity is the dose limiting side effect but this is now completely ameliorated by simply hydrating the patient. The drug in combination therapy, has proven to be 'potentially curable' for all form of testicular cancer. Other cancers where the drug activity has begun to approach this are head and neck cancer, and ovarian cancer. Activity against the other major cancers is now being studied. The mechanism of action at a molecular level appear to depend upon a primary lesion formed on the cellular DNA by the platinum complex. This serendipitous discovery has led to a new class of anticancer agents, metal coordination complexes, which may prove to be of significant value.     

On the intrinsic accuracy and precision of luminescence dating techniques for fired ceramics

Luminescence dating techniques have been used extensively for archaeological and geological samples. Such techniques are based on thermally or optically stimulated signals. This paper presents simulations of several luminescence techniques for equivalent dose (ED) estimation for ceramic materials containing quartz. The simulations are carried out using a recently published comprehensive kinetic model for quartz, consisting of 11 electron and hole traps and centers. The complete sequence of the experimental protocols for several thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques are simulated using the same set of kinetic parameters. The specific simulated protocols are: additive dose TL protocol, predose technique (both additive and multiple activation versions), phototransfer protocol, single aliquot regenerative optically stimulated luminescence (SAR-OSL) protocol, and SAR thermoluminescence protocol (SAR-TL). One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The intrinsic accuracy of these techniques is estimated by simulating natural irradiation of the samples with a known burial dose, followed by simulation of the luminescence method used to recover the estimated dose ED. The percent difference between the burial dose and the ED value represents the simulated accuracy of the luminescence technique. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the ED values obtained with the 100 model variants. It is found that the various techniques can reproduce natural paleodoses in the range 10 mGy–10 Gy with a typical intrinsic accuracy of +1 to 10%. Techniques based on single aliquot protocols were found in general to be more precise than techniques requiring the use of multiple aliquots. In addition, techniques based on interpolation of experimental data were found to be consistently both more precise and accurate than those based on extrapolation of experimental data.     

Constraints on the precision of SAR in equivalent dose estimations close to saturation in quartz

Difficulties in evaluating accurate equivalent doses for Late Quaternary sediments from the south coasts of Greece arose in the course of SAR measurements. Large scatter among apparent equivalent doses perplexed the evaluation of accurate mean estimates in circumstances where very large doses were involved. Besides, dose recovery experiments revealed that when intersection of the natural signal occurs onto the saturating segment of the growth curve, a distinct relationship between D_e and growth curve shape occurs. At very low slope angles, SAR tends to overestimate the recovered dose. The mechanism which controls the spread in equivalent dose estimation is investigated.     

OSL and TL dating of the Middle Stone Age sequence at Diepkloof Rock Shelter (South Africa): a clarification

Diepkloof Rock Shelter offers an exceptional opportunity to study the onset and evolution of both Still Bay (SB) and Howiesons Poort (HP) techno-complexes. However, previous age estimates based on luminescence dating of burnt quartzites (Tribolo et al., 2009) and of sediments (Jacobs et al., 2008) were not in agreement. Here, we present new luminescence ages for 17 rock samples (equivalent dose estimated with a SAR-ITL protocol instead of classical MAAD-TL) as well as for 5 sediment samples (equivalent dose estimated with SAR-single grain OSL protocol) and an update of the 22 previous age estimates for burnt lithics (modified calibration and beta dose estimates). While a good agreement between the rock and sediment ages is obtained, these estimates are still significantly older than those reported by Jacobs et al. (2008). After our own analyses of the sediment from Diepkloof, it is suspected that these authors did not correctly chose the parameters for the equivalent dose determination, leading to an underestimate of the equivalent doses, and thus of the ages.