E.M. Scott

Radiometric investigations of Kara Sea sediments and preliminary radiological assessment related to dumping of radioactive wastes in the Arctic Seas

There has been world-wide concern over the possible health and environmental impacts of the dumping of radioactive wastes in shallow waters of the Kara and Barents Seas. During 1992, IAEA-MEL participated in a joint Russian-Norwegian expedition to the region and collected a suite of sediment cores for characterization of downcore radioactivity distribution patterns and inventories with the aim of assessing past and present inputs of radionuclides. The 137Cs, 238Pu, 239,240Pu, and 241Am contents of the 0–1 cm sections range from 17 to 32, 0·01 to 0·06, 0·4 to 1·3 and 0·2 to 0·5 Bq kg−1 (dry wt), respectively. The 238Pu/239,240Pu and 241Am/239,240Pu activity ratios are consistent with those reported for global fallout. Detailed information on downcore radionuclide distribution patterns and inventories, as well as an account of sedimentation parameters, are presented. A preliminary assessment of the long-term radiological impact of radioactive waste disosal in the Arctic Seas, on global and regional scales, has been made. The modelling results suggest that the global radiological impact of the disposals will be comparable to or less than those resulting from other anthropogenic and natural sources of radioactivity. However, radiological effects on the regional scale may be of importance. IAEA is carrying out a 4 year International Arctic Seas Assessment Project (IASAP) that will comprehensively cover all aspects of radioactive dumping in the Arctic Seas and it will be reported to the London Convention in 1996. The IAEA-MEL study described here represents a preliminary contribution to IASAP.

Accounting for spatial variability and fields of view in environmental gamma ray spectrometry

Abstract Spatial variability is an important feature in many environmental studies, which influences comparison estimates of environmental radioactivity from soil samples and in-situ or airborne γ-ray spectrometry. Comparisons between ground based and airborne gamma ray spectrometry are needed both for interpretation and for calibration purposes. However, under normal environmental conditions such comparisons may be affected by the considerable differences in the spatial response of these measurement techniques. A sampling methodology is presented which enables soil sample derived estimates of environmental radioactivity to be effectively compared with in-situ and aerial survey results. Examples of calibration sites and derived sensitivity estimates for 137 Cs are presented for a range of environmental contexts.

Estimating and accounting for 137Cs source burial through In-situ gamma spectrometry in salt marsh environments

Abstract The use of in-situ gamma ray spectrometry provides a means of rapidly estimating environmental radioactivity inventories. However, one of the principal limitations of this technique has been the influence of variations in vertical activity distribution on the observed photon fluence. This paper demonstrates that the quantification of the forward scattered ratio of the spectrum ( Q ) can be used to: (i) estimate the mean mass depth (β) of the vertical activity distribution within sediment profiles, and (ii) provide a calibration correction coefficient for in-situ gamma spectrometry in environments which exhibit variable and non-exponential activity distributions, such as salt marshes around the Irish Sea. This paper presents a successful application of a spectrally derived calibration correction coefficient to in-situ spectra from a salt marsh at Caerlaverock, Dumfries, SW Scotland, improving the correlation between soil core and in-situ derived activity estimates from r 2 = 0.097 (uncorrected) to r 2 = 0.801 (corrected). The scope for extending this approach to a wider range of environments, to airborne gamma spectrometry and to measurements of sedimentation rates is considered.

Carbon-14 discharges from the nuclear fuel cycle: 1. Global effects

The radiological impact of 14C produced by the nuclear fuel cycle is assessed using an advanced 25-box model of the carbon cycle coupled with a range of feasible energy-use scenarios. In particular, this study estimates both the short- and long-term dose implications to the global population. In the former context, it is predicted that the atmospheric 14C specific activity in the year 2050 will be 234 Bq kg−1 (carbon), corresponding to delivery of an individual effective dose equivalent rate of 15 μSv year−1. The contribution of reactor-derived 14C to the individual dose rate increases steadily throughout this period, reaching 1·8 μSv year −1 in 2050, well within ICRP limits. In the longer term, however, the collective effective dose equivalent commitment is conservatively estimated at 141 man Sv TBq−1, corresponding to 480 man Sv (GW(e) year)−1. These figures indicate that 14C could generate one of the largest contributions to the total dose to man from nuclear power production.

Technological enhancement of natural radionuclides in the marine environment

This review summarizes aspects of technologically enhanced radioactivity in the UK marine environment, considers briefly related investigations in western Europe and then discusses some models for the kinetics of series decay and ingrowth which can be applied to technological inputs of series members to the marine environment and to their differential elemental biogeochemistries.

Adherence of arthroconidia and germlings of anthropophilic and zoophilic varieties of Trichophyton mentagrophytes to human corneocytes as an early event in the pathogenesis of dermatophytosis.

The association (adherence) between human corneocytes and arthroconidia of Trichophyton mentagrophytes strains 121 and 126, and T. interdigitale strain 4 was studied in vitro. Adherence of arthroconidia to corneocytes from either the palm and sole occurred and increased with time up to 6 h, by which time germination of arthroconidia had started. Significant differences were seen between the T. mentagrophytes strains and T. interdigitale in their adherence to corneocytes from the palm. When adherence values for plantar corneocytes were compared, significant differences were found between T. mentagrophytes had T. interdigitale. Not all corneocytes from either site had adherent arthroconidia, although there was a time‐dependent increase in the numbers of corneocytes with adherent fungal cells. By scanning and transmission electron microscopy it was seen that there was a loose association between arthroconidia and corneocytes with no apparent damage to the corneocytes membrane. Adherence of germlings of T. interdigitale to corneocytes from the palm appeared to be mediated by germling outer cell wall fibrils. Hyphal branches and secondary germlings were observed to enhance the attachment of the parent hypha to adjacent corneocytes.

Early events in the invasion of the human nail plate by Trichophyton mentagrophytes.

A new in vitro model for the study of nail invasion by dermatophyte fungi was developed. The dermatophyte Trichophyton mentagrophytes, and fragments of finger‐nails and toe‐nails were used. Arthroconidia were inoculated on the ventral surface of the nails. After 6h. adherence and germination of arthroconidia was observed. By 16th, small germ tubes with side branches were evident. At about 24 h. micro‐colonies had become established. At 48 h, a mycelium had formed, and at about 72 h most of the nail fragment was covered with fungal growth. Nail penetration occurred from the ventral surface through the intercellular spaces, and with longer incubation all three layers were invaded by arthroconidia growing through channels. Nail invasion occurred in the absence of added nutrients. Dermatophyte fungi appeared to invade the nail by a combination of mechanical and chemical factors. The model provides a substrate to study the pharmacokinetics and bioavailability of new antifungal agents in situ.

A Role for the Long Noncoding RNA SENCR in Commitment and Function of Endothelial Cells

Despite the increasing importance of long noncoding RNA in physiology and disease, their role in endothelial biology remains poorly understood. Growing evidence has highlighted them to be essential regulators of human embryonic stem cell differentiation. SENCR, a vascular-enriched long noncoding RNA, overlaps the Friend Leukemia Integration virus 1 (FLI1) gene, a regulator of endothelial development. Therefore, we wanted to test the hypothesis that SENCR may contribute to mesodermal and endothelial commitment as well as in endothelial function. We thus developed new differentiation protocols allowing generation of endothelial cells from human embryonic stem cells using both directed and hemogenic routes. The expression of SENCR was markedly regulated during endothelial commitment using both protocols. SENCR did not control the pluripotency of pluripotent cells; however its overexpression significantly potentiated early mesodermal and endothelial commitment. In human umbilical endothelial cell (HUVEC), SENCR induced proliferation, migration, and angiogenesis. SENCR expression was altered in vascular tissue and cells derived from patients with critical limb ischemia and premature coronary artery disease compared to controls. Here, we showed that SENCR contributes to the regulation of endothelial differentiation from pluripotent cells and controls the angiogenic capacity of HUVEC. These data give novel insight into the regulatory processes involved in endothelial development and function.

The preservation of medically important fungi

Details are given of a method, first described in 1962, for preservation of fungi in anhydrous silica gel. It is shown that the procedure is suitable for use with dermatophytes, yeasts and other fungi of medical importance and that they may be preserved for periods of 5 years or more.

Superficial mycoses in the west of Scotland.

Ringworm formed almost 70 per cent of all superficial mycoses diagnosed. The feet and nails were most frequently affected and a single species, Trichophyton rubrum was responsible for the majority of infections that required specialist attention. Scalp ringworm which, until the middle of this century, was the most common form of the disease now constitutes only 5 per cent of infections and the majority of these are caused by the zoophilic fungus Microsporum canis. The anthropophilic dermatophytes which were once so prevalent as the cause of scalp infections are now rarely encountered. Yeasts, especially Candida albicans were most frequently encountered as a cause of mucosal infections but were not unimportant as a cause of disease of skin and nail.