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  • Author or Editor: N. Spyrou x
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Abstract  

Nuclear and atomic methods of analysis, which rely on the detection of prompt and delayed radiations, emitted as a result of interactions between radiation probe and target, for determining the elemental concentration in vivo and in vitro, are summarily reviewed, with reference to bone analysis; the demand for methods which provide information about elemental distribution is highlighted. The way neutrons can be used as probes to investigate the composition and structure of objects by employed the principles of computerised tomography are outlined and the novel modes of utilisation are briefly described: neutron transmission tomography, neutron induced prompt gammaray emission tomography and neutron induced delayed gamma-ray emission tomography. The latter method, alternatively termed neutron activation tomography, is then used to determine on-destructively the distribution of Na in selected planes of a human tibia, in vitro, by measuring the activity of24Na using a NaI(Tl) and a Ge(Li) detector in a tomographic scanner which incorporates a microcomputer for control, data acquisition and image reconstruction. The problems of attenuation and scattering are discussed as are the limitations for quantitative results of this useful new mode of tomography which provided information about composition and elemental distribution in a material.

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Abstract  

Developments in neutron activation analysis in its various modes for trace element determination are described with reference to reactor and other neutron sources, competing methods, tomography and detection systems. A selected number of areas of application are highlighted which provide challenges into the next millennium and to which a useful and in some cases a unique contribution can be made. The role that neutron activation analysis can play in decommissioning, landmine detection, boron neutron capture therapy, Alzheimer's disease, diabetes mellitus, the complex mechanisms of initiation and termination of feeding and obesity as well as in scar formation and the requirements for artificial skin are presented.

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Abstract  

Betel nut chewing (Areca catechu), whether plain or wrapped insidea betel leaf quid together with other substances including tobacco,has been reported as a cause of the high incidence of oral and oesophagealcancers in Asian communities worldwide. Chewing of such substances resultsin the formation of nitrosamines, some of which may be diabetogenic to man.The incidence of Type 2 diabetes is particularly prevalent amongst Asian immigrantsliving in the UK and as part of a larger study we have analysed a number ofpopular betel nut based chewing materials to determine their elemental composition.Instrumental neutron activation analysis was used for determination of elementalconcentrations of short-lived radionuclides. Ag, Al, Br, Ca, Cl, Cu, Dy, K,Mg, Mn, Na, Ti, and V were detected, some of which are implicated in diabetes.Concentrations of these, except for Ag, Dy and Ti, are reported and comparedwith values found in betel-nut and chewing materials from Taiwan. It is indicatedthat for certain elements the amount ingested by betel-nut chewers may bea significant fraction of their daily dietary intake.

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Abstract  

The influence of stages of lactation on the mineral and trace elementconcentrations of breast milk collected from 20 healthy lactating women ina Nigeria population was investigated using instrumental neutron activationanalysis (INAA) and proton induced X-ray emission (PIXE) analysis. The breastmilk samples were divided into colostrum (day 1–5), transitional (day6–13) and mature milk (day 14–28). The result of the study showthat colostrum milk has a significantly higher mean concentration of Ca, Cl,Cu, Fe, Mg, Na and Zn than the transitional and mature milk. Furthermore,the mean concentrations of Fe, Mg, Na and Zn in transitional milk were foundto be significantly higher when compared with the mature milk. It was alsoobserved from the semi-log plot of the concentration of the elements againstdays of lactation that the concentration of all the elements decreased significantlythroughout the lactation period studied with Cu, Fe and Zn concentration showingthe greatest decline, particularly in the early stages of lactation.

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Abstract  

Where human health worldwide is under threat, radioanalytical and imaging scientists are expected to make significant difference and contribution. Diabetes, malnutrition, Alzheimer’s and cardiovascular diseases can be better understood by probing elemental distributions to nano-scales and quantifying elemental compositions to ultratrace levels. As we aim towards personalized medicine, cancer management awaits new diagnostic and therapy methods which account, for example, for tissue oxygenation. In the context of such biomedical issues, recent trends and future developments are presented taking into consideration the availability of research reactors and ion beam facilities, as well as alternative and emerging techniques such as PIXE tomography (PIXE-T) and two-and three-gamma PET.

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Abstract  

Expressions for the calculation of minimum detectable mass and length fractions of elements, compounds and mixtures in a sample using neutron attenuation coefficients are derived, based on previous work done with photon attenuation coefficients. These expression allow quantitative information about elemental concentration to be extracted from neutron transmission measurements and neutron transmission tomography. Calculations are carried out for the detectable mass fraction of hydrogen in a number of sample matrices of industrial interest and of elements in a water matrix highlighting the differences with photon attenuation measurements. Results are presented for three neutron energies, cold (0.001 eV), thermal (0.025 eV) and fast (14 MeV).

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Abstract  

The setting of cyclic activation and its development in a historical context is attempted and a case is made for the usefulness of the method in the analysis of materials via short-lived isotopes. The theory of cyclic activation analysis is presented and the resulting detection limits shown to be superior to the conventional one-shot irradiation-counting sequence. The possibility of determining the half-life of an isotope from the data accumulated in the same experiment is also highlighted. Problems and applications are illustrated by experimental results obtained from a variety of sample matrices, mainly biological and environmental, with the use of a reactor irradiation facility, since the use of both isotopic neutron sources and neutron generators are discussed elsewhere. It should therefore be viewed as a personal and selective review of the field. Epithermal cyclic neutron activation analysis is suggested as an area demanding consideration and a new cyclic activation system is introduced.

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Abstract  

The objective of this study was to evaluate the concentrations of essential and toxic elements in hair of children in Tanzania in order to assess their nutritional status. 141 samples of hair from boys and girls living in Tanzania were analyzed using instrumental neutron activation analysis (INAA). The mean concentration levels of Zn and Cu were lower whilst those of other elements were in the same range as the hair elemental concentrations reported in the literature. The lower concentrations of Zn might be related to the diet of mainly cereals with low animal proteins consumed by most of the Tanzanian population.

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Abstract  

The concentrations of elements in rice, locally cultivated in two regions of Tanzania (Mbeya and Morogoro), were determined using Instrumental Neutron Activation Analysis (INAA) for Na, Mg, Al, Cl, K, Ca, V, Mn, Cu and Br, and Particle-Induced X-Ray Emission (PIXE) for P, Fe and Zn. There were no statistical differences in concentrations of the essential elements Fe, Zn, Cu and P in rice from both regions. There was also no significant correlation between grain P and Fe content, suggesting the possibility of growing Tanzanian rice with low phytic acid and high Fe contents.

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Abstract  

In this study an investigation into the applicability of the absolute method in Prompt Gamma-ray Neutron Activation Analysis (PGNAA) was undertaken. Although the system parameters are adequately characterized, the scatter in nuclear data for a number of elements is significant. For our particular experimental set up the K-factors were calculated for a number of elements using both Au and Fe as monostandards. A comparison was made between the calculated and experimentally determined K-factors and from this comparison the feasibility of the absolute method in neutron prompt gamma-rays can be realized for a number of elements.

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