Applying nitrogen site-specifically using soil electrical conductivity maps and precision agriculture technology.

Soil texture varies significantly within many agricultural fields. The physical properties of soil, such as soil texture, have a direct effect on water holding capacity, cation exchange capacity, crop yield, production capability, and nitrogen (N) loss variations within a field. In short, mobile nutrients are used, lost, and stored differently as soil textures vary. A uniform application of N to varying soils results in a wide range of N availability to the crop. N applied in excess of crop usage results in a waste of the grower"s input expense, a potential negative effect on the environment, and in some crops a reduction of crop quality, yield, and harvestability. Inadequate N levels represent a lost opportunity for crop yield and profit. The global positioning system (GPS)-referenced mapping of bulk soil electrical conductivity (EC) has been shown to serve as an effective proxy for soil texture and other soil properties. Soils with a high clay content conduct more electricity than coarser textured soils, which results in higher EC values. This paper will describe the EC mapping process and provide case studies of site-specific N applications based on EC maps. Results of these case studies suggest that N can be managed site-specifically using a variety of management practices, including soil sampling, variable yield goals, and cropping history.

Supporting cancer care in the developing countries: role of IAEA/WHO.

Cancer management can be expensive and constitutes a major problem in many developing countries where management standards are poor due to many factors, including non-availability of sufficient funds, equipment, and trained personnel. The incidence of cancer is rising worldwide. This is more so in the developing countries, many of whom are less equipped to deal with the problems. Radiation therapy is one of the major treatment modalities for cancer, and it is estimated that about 60% of all cancer patients require this treatment at one time or another during the course of their disease. Unfortunately, radiotherapy facilities are lacking or grossly inadequate in many developing countries. Over the past 8 years the IAEA and WHO have shown more interest in the problem and treatment of cancer in the developing countries. This paper reviews the role of these international organizations, with emphasis on research activities, education (seminars, workshops, training courses), and technical assistance programs. These include establishment or upgrading of radiotherapy facilities, provision of experts, etc. Scientific papers are published with a view to disseminating current information and research findings in the developing countries. The achievements up to date are assessed and discussed.

An overview of the situation in radiotherapy with emphasis on the developing countries.

Radiotherapy services are closely linked to the level of medical care which, in turn, is an important component of the overall health care program, with its development related to social, economic, and educational factors. As a basis for understanding the situation regarding adequate coverage of the population by radiotherapy services, general information about the world population (currently 5 billion), age distribution, frequency of cancer occurrence, and causes of death is presented. For an appreciation of the obstacles that must be overcome, the situation with regard to Gross National Product (GNP), transfer of economic resources, and per capita expenditures for health services is shown. For example, in the developing world, most countries spend less than 5% of their GNP for health, and on a macro scale at least 20 billion U.S. dollars per year are being transferred from the poor nations of the southern hemisphere to the northern hemisphere. Information about the wide range of population coverage with radiotherapy resources and the trend regarding high-energy radiotherapy machines is presented. For example, in North America (USA) there are six high-energy machines for each one million persons, and each machine is used to treat about 230 new patients per year. In other parts of the world, such as large areas of Africa and South-East Asia, there may only be one high-energy radiotherapy machine for 20 to 40 million people, and one machine may be used to treat more than 600 new patients per year. Many cancer patients have no access to radiotherapy services. When estimates of the need for radiotherapy services in the developing world as a consequence of cancer incidence are compared with the current health expenditures, it is concluded that a combined effort of national authorities, donor and financial institutions, professional and scientific societies, and international organizations is required. The knowledge, skills, and technology are available in many excellent radiotherapy centers throughout the world. The key issues are priority and the commitment of sufficient resources.

The IAEA/WHO TL dosimetry service for radiotherapy centres 1969-87.

The International Atomic Energy Agency (IAEA) started a postal dosimetry service in 1966 using lithium fluoride (LiF) thermoluminescent dosimeters (TLD). The World Health Organization (WHO) joined the programme in 1968. Dosimeters were sent on 29 occasions to primary standards laboratories or to the 'Bureau International des Poids et Measures' to guarantee the traceability to primary standards of absorbed dose. The mean deviation was -0.26 +/- 0.18% (1% SD of the mean). One SD for a single result was about 1%. The number of intercomparisons made during the whole period is about 2,000 from about 700 radiotherapy centres in 89 countries. To date only 60Co machines have been included. The mean deviation of all the results from the centres was -0.25, and 1% SD for a single result 6.7%. About 5% of the centres had deviations larger than 30%, at least on one occasion. It is shown that the accuracy in dosimetry improves considerably for those departments participating more than once in the TL dosimetry service.

Photochemical oxidants: effect on starch hydrolysis in leaves.

Starch-filled leaves of plants which have been subjected to low dosages of naturally occurring photochemical oxidants, ozone, or peroxyacetyl nitrate hydrolyze their starch more slowly when placed in the dark. Delayed hydrolysis occurs irrespective of whether the oxidants were applied during the light or dark period. Occasionally this effect is evident only in the intervenal areas.