Non-linearity of pre-dose response and its effects on TL dating

Analytical expressions for thermoluminescence (TL) dating based on the modified Zimmerman model were derived. The non-linear behaviour of TL sensitivity is reexamined and is found to be due to electron capturing competitions in both test-dose excitation and the readout stages. A curve fitting method is proposed to determine the paleodose for the additive dose dating method. The multiple activation technique is also investigated, from which the paleodose should be regarded as an upper limit.     

A combination of ultrasound and oxidative enzyme: sono-enzyme degradation of phenols in a mixture

Sono-degradation and sono-enzyme degradation of phenols were performed on the mixtures of double compounds (phenol, p-chlorophenol; phenol, p-cresol; phenol, p-nitrophenol; and p-chlorophenol, p-cresol) in aqueous medium. Sono-degradation of phenol and its substituted compounds individually behaved approximately the same, but in the case of mixture behaved differently. Sono-degradation of substituted phenols was easier than phenol in a mixture, but there was an exception in the combination of phenol and p-nitrophenol that the degradation of phenol was faster than substituted compound. This behavior was the same in sono-enzyme degradation, but with higher degradation rate. Between these mixtures, the combination of phenol and p-cresol presented a significant different behavior in case of single and double compounds solutions. In this system, the sono-degradation of phenol in mixture was more difficult than phenol alone but, the sono-degradation of p-cresol in mixture was easier in comparison with p-cresol alone. In sono-enzyme degradation, p-cresol as a more reactive compound facilitated the remove of phenol in mixture in compare of the individual case.     

On the dose-rate estimate of carbonate-rich sediments for trapped charge dating

In a wide range of environmental conditions sediments are subject to changing water content and carbonate cementation during burial. Trapped charge dating of these carbonate-rich deposits requires the determination of a dose rate which is not constant during burial because sediments were subject to post-depositional geochemical alterations. The dose-rate model established in this study assumes linear increase of carbonate mass and linear decrease of water mass in pores between sediment particles during burial. Numerical modelling assesses the effect of carbonate and water on the infinite-matrix dose rate as a function of time. Sensitivity testing of the system indicated that water and carbonate content have the greatest effect on the resulting dose rate, followed by the timing of onset and completion of carbonate formation. As a consequence, a comprehensive re-calculation of the water correction factors was undertaken. It revealed a 5% lower value for the annual beta dose and a 10% lower value for the annual gamma dose compared to values formulated by Zimmerman [1971. Thermoluminescence dating using fine grains from pottery. Archaeometry 13, 29–52].

The dose-rate model was tested using samples from geologically well-constrained coastal sites. The differences between onset and final dose rate were up to 30% resulting in differences between modelled and conventional optical ages between 2% and 15% depending on the final (today's) water and carbonate content. The divergence of dates may be greater under certain conditions. The dose-rate model can be applied to a wide range of contexts similar to those considered in this case study.     

Theoretical analysis of sonochemical degradation of phenol and its chloro-derivatives

Phenol and its chloro-derivatives contribute significantly to environmental pollution hazards due to their high degree of toxicity as well as improper disposal methods. Cavitation can be used successfully for degradation of phenolic compounds and the rates of degradation are dependent on the type of the primary pollutant in the system. In the present work, a theoretical explanation has been provided to explain the observed degradation trends of phenol and chlorophenols on the basis of concentration of the pollutant at the cavitation bubble/solution interface. Chemical stability of these compounds towards radical attack in the liquid phase has been discussed. It has been observed that chloro-derivates degrade much faster as compared to the parent compound due to higher hydrophobicity of chloro-derivates.     

Ultrasound-assisted oxidative desulfurization of liquid fuels and its industrial application

Latest environmental regulations require a very deep desulfurization to meet the ultra-low sulfur diesel (ULSD, 15 ppm sulfur) specifications. Due to the disadvantages of hydrotreating technology on the slashing production conditions, costs and safety as well as environmental protection, the ultrasound-assisted oxidative desulfurization (UAOD) as an alternative technology has been developed. UAOD process selectively oxidizes sulfur in common thiophenes in diesel to sulfoxides and sulfones which can be removed via selective adsorption or extractant. SulphCo has successfully used a 5000 barrel/day mobile “Sonocracking” unit to duplicate on a commercial scale its proprietary process that applies ultrasonics at relatively low temperatures and pressures. The UAOD technology estimate capital costs less than half the cost of a new high-pressure hydrotreater. The physical and chemical mechanisms of UAOD process are illustrated, and the effective factors, such as ultrasonic frequency and power, oxidants, catalysts, phase-transfer agent, extractant and adsorbent, on reaction kinetics and product recovery are discussed in this review.     

Development and characterisation of an XeCl excimer laser-generated soft-X-ray plasma source and its applications

Summary A large-aperture, long-pulse XeCl excimer laser has been used to generate a soft-X-ray plasma source. Several laser optical configurations have been employed to optimise X-ray emission, including positive-branch unstable resonators and injection by seeding the gain region of the laser with a small commercial excimer laser, resulting in power densities in the range 10¹²–10¹⁴ W cm⁻². The characteristics of the plasma source for each different laser configuration and for different target materials are investigated. The most suitable source conditions (spectral energy distribution, time duration, etc.) for specific applications are discussed. Supported by the Royal Society, UK. Supported by INFM, Italy.     

Near- to far-field characterization of a parametric loudspeaker and its application in non-destructive detection of detachments in panel paintings

The particular properties of the parametric loudspeaker make this class of sources an attractive investigation tool especially for non-destructive testing (NDT). Recently actual applications mainly in the field of material’s acoustical characterization are emerging. The authors present the analysis of the pressure field generated by a commercial parametric loudspeaker both in the near- and far-field, aiming at the understanding of the modality of its employment as excitation source in a measuring system. Successively the parametric source was integrated in a system purposely developed for acoustic diagnostics on objects of heritage interest. It was used in an in situ investigation on the renaissance panel painting Annunciazione by the Italian artist Benozzo Gozzoli (XV century) revealing pictorial film detachments. Preliminary results are here presented, disclosing the potential of the parametric loudspeaker for the enhancement of the spatial resolution in the acoustic measurement, of the non invasiveness of the investigation tool, and also of the operator comfort.     

Concepts and methods of ESR dating

Electron spin resonance (ESR) dating is an absolute dating method suitable for the Quaternary which can be applied to a wide range of materials. It is based on determining the natural radiation dose to which a sample has been exposed during its burial period. This paper outlines the basic concepts, and reviews recent studies on the methods and models of ESR dating.

Scope of this paper. This review paper is one of two in this volume providing an overview of recent developments in the field of electron spin resonance (ESR) dating. The paper focuses on studies investigating the fundamental concepts and methods employed in ESR dating, while the companion paper by Rink (this issue) focuses on applications of the method. Previous review articles have been published by Ikeya (1978) and Ikeya (1985), Hennig and Grün (1983), Nambi (1985) and Grün (1989b). Subsequently, papers by Grün (1991), Schwarcz (1994) and Ikeya (1994a); Ikeya (1994b) and Ikeya (1994c) have reviewed specific aspects of the field. There are three books on ESR dating by Ikeya (1986), in Japanese), Grün (1989a)Grün (1989b), in German) and Ikeya (1993), in English) respectively. In view of the coverage of previous reviews of the field, this paper concentrates on research undertaken since 1990.

The first part introduces and outlines the basic ideas of ESR and its application to dating. This is followed by an overview of recent studies concerned with the basic concepts of the field, its methods and models, as independently of specific materials as possible.     

Iron oxide nanoparticle synthesis in aqueous and membrane systems for oxidative degradation of trichloroethylene from water

The potential for using hydroxyl radical (OH^?) reactions catalyzed by iron oxide nanoparticles (NPs) to remediate toxic organic compounds was investigated. Iron oxide NPs were synthesized by controlled oxidation of iron NPs prior to their use for contaminant oxidation (by H₂O₂ addition) at near-neutral pH values. Cross-linked polyacrylic acid (PAA) functionalized polyvinylidene fluoride (PVDF) microfiltration membranes were prepared by in situ polymerization of acrylic acid inside the membrane pores. Iron and iron oxide NPs (80–100 nm) were directly synthesized in the polymer matrix of PAA/PVDF membranes, which prevented the agglomeration of particles and controlled the particle size. The conversion of iron to iron oxide in aqueous solution with air oxidation was studied based on X-ray diffraction, Mössbauer spectroscopy and BET surface area test methods. Trichloroethylene (TCE) was selected as the model contaminant because of its environmental importance. Degradations of TCE and H₂O₂ by NP surface generated OH^? were investigated. Depending on the ratio of iron and H₂O₂, TCE conversions as high as 100 % (with about 91 % dechlorination) were obtained. TCE dechlorination was also achieved in real groundwater samples with the reactive membranes.     

Hydrogen degradation of steels and its related parameters,a review

Many steel structures can absorb varying amounts of hydrogen during manufacturing, processing such as electroplating or acid pickling and during service life by corrosion reactions or cathodic protection. Hydrogen is known to have a devastating effect on strength and ductility of iron and steel components. Many studies have been done on the detrimental effects of hydrogen on iron and different steel structures but there is a need for comprehensive research to cover all related parameters which can control the extent of hydrogen interaction and degradation in steels. In this review, at first hydrogen uptake and different damages associated with absorbed hydrogen in steels are discussed. Then, the effective parameters in the extent of hydrogen interaction and degradation, especially hydrogen embrittlement which is more common in steel components are reviewed.     

On the characterisation of interfacial defects using high resolution electron microscopy

The characterisation of line defects in interfaces, observed using high-resolution electron microscopy, is discussed. Characterisation is carried out by mapping a closed circuit initially constructed around a defect into a reference space. This process has been generalised to incorporate operations other than translations, and has also been expressed mathematically, and thereby related to recent developments based on symmetry theory. Examples of the characterisation of dislocations in twin interfaces in hexagonal-close-packed crystals and an interfacial dispiration are presented as illustrations.     

FTIR in situ transmission studies on the kinetics of paper degradation via hydrolytic and oxidative reaction paths

This study deals with the quantitative and qualitative interpretation of transmission FTIR spectra of aged model paper samples to prepare the basis for a kinetic model of cellulose degradation involving mixed hydrolytic and oxidative mechanism. The ageing experiments were performed in situ under various conditions (pure water vapour, dried air, 100, 150 °C) to discriminate between hydrolytic and oxidative paths. Our focus was on the spectra between 1500–1900 cm^-1, where the products of paper ageing appear in the form of various carbonyl groups. A procedure of spectra standardization was used to interpret the bands area in terms of the conversion of carbon atoms in cellulose. From the time evolution of the bands the overall kinetic curves were generated. The positions of the carbonyl bands were verified by independent experiments and theoretical calculations (DFT method). A simple model involving a hydrolytic reaction route and first order kinetics was positively tested on the available experimental basis. PACS 81.05.-t; 82.20.Wt; 87.15.Rn     

Thermoelastic generation of elastic waves for non-destructive testing and medical diagnostics

The generation of MHz elastic waves by means of thermoelastic expansions is described. Several multilayered structures are described which use constrained boundary conditions at the energy absorbing surface. Elastic waves of sufficient amplitude can be generated to be useful for non-destructive testing applications. Biomedical ultrasonics using thermoelastically generated MHz waves will also be discussed.     

Design and construction of short pulse ultrasonic probes for non-destructive testing

This paper describes the design and construction of 10 MHz compressional wave ultrasonic ndt probes for use in situations where operation with the shortest possible pulse length (and hence greatest bandwidth) is of prime importance. Tungsten-loaded epoxy backing blocks are manufactured separately before incorporation into probes, the manufacturing technique allowing lossy, high impedance backings to be constructed both with ease and with the use of very little manufacturing equipment. After preparation, transducers and backings are assembled into probes using simple construction jigs.Results are given showing that the 10 MHz probes thus constructed operate satisfactorily both in contact and in immersion testing. Probes of other centre frequencies can be manufactured using the same technique.     

On the effects of NBTI degradation in p-MOSFET devices

This paper presents the effects of interface trap concentration and threshold voltage shift on NBTI degradation in p-MOSFETs. To explore the degradation mechanisms, transistors having an EOT of 1.1 nm and 5 nm were simulated by applying various stress conditions. The NBTI degradation mechanism was studied by varying the gate voltage, temperature and substrate doping level. The simulations show NBTI degradation in terms of the threshold voltage shift, ΔV_th and number of interface traps, ΔN_it. The simulation results show an improved degradation trend in terms of ΔV_th and ΔN_it when the substrate doping level is increased.     

Ultrasonic degradation of N-di and trihydroxy benzoyl chitosans and its effects on antioxidant activity

Modified chitosans with 3,4-dihydroxy benzoyl groups (CS-DHBA) and 3,4,5-trihydroxy benzoyl groups (CS-THBA) were synthesized and their chemical structures were determined by Fourier transform infrared (FT-IR) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. Then, ultrasonic degradation of CS, CS-DHBA and CS-THBA in 1% acetic acid solution was investigated. The kinetics studies of degradation were followed by gel permeation chromatography (GPC). The results indicated that the weight-average molecular weight of chitosan decreased obviously after ultrasound treatment, but molecular weights of CS-DHBA and CS-THBA decreased slowly with increasing sonication time. Degradation kinetics model based on 1/M_t−1/M₀ = kt was used to estimate the degradation rate constant. It was found that the rates of degradation of CS-DHBA and CS-THBA are lower than CS, and follow the order: CS₄ > CS₈ > CS₁₂ > CS-THBA₄ > CS-THBA₈ ≈ CS-DHBA₄ > CS-THBA₁₂ > CS-DHBA₈ > CS-DHBA₁₂. The antioxidant activity of the CS, CS-DHBA and CS-THBA before and after sonication was investigated by the radical scavenging activity method using 1,1-diphenyl-2-picrylhydrazyl (DPPH). The DPPH scavenging free radical capacity of CS-THBA and CS-DHBA increased up to 89% and 74% respectively, when the concentration reached 6 μg/ml. The ultrasonic treatment of CS-DHBA and CS-THBA after 30 min decreased the DPPH free radical scavenging activity but ultrasonic treatment of CS increased the DPPH free radical scavenging activity.