RESUMEN
Ultraviolet radiation (UV) is a minor fraction of the solar spectrum reaching the ground surface. In this assessment we summarize the results of previous work on the effects of the UV-B component (280-315 nm) on terrestrial ecosystems, and draw attention to important knowledge gaps in our understanding of the interactive effects of UV radiation and climate change. We highlight the following points: (i) The effects of UV-B on the growth of terrestrial plants are relatively small and, because the Montreal Protocol has been successful in limiting ozone depletion, the reduction in plant growth caused by increased UV-B radiation in areas affected by ozone decline since 1980 is unlikely to have exceeded 6%. (ii) Solar UV-B radiation has large direct and indirect (plant-mediated) effects on canopy arthropods and microorganisms. Therefore, trophic interactions (herbivory, decomposition) in terrestrial ecosystems appear to be sensitive to variations in UV-B irradiance. (iii) Future variations in UV radiation resulting from changes in climate and land-use may have more important consequences on terrestrial ecosystems than the changes in UV caused by ozone depletion. This is because the resulting changes in UV radiation may affect a greater range of ecosystems, and will not be restricted solely to the UV-B component. (iv) Several ecosystem processes that are not particularly sensitive to UV-B radiation can be strongly affected by UV-A (315-400 nm) radiation. One example is the physical degradation of plant litter. Increased photodegradation (in response to reduced cloudiness or canopy cover) will lead to increased carbon release to the atmosphere via direct and indirect mechanisms.
Asunto(s)
Cambio Climático , Ecosistema , Energía Solar , Rayos Ultravioleta/efectos adversos , Animales , Humanos , Plantas/efectos de la radiación , Monitoreo de RadiaciónRESUMEN
Brain function in severly malnourished children was assessed, using computer analysis of electroencephalographic (EEG) responses to photic driving at different frequencies during slow-wave sleep. Percentage power in the classical EEG broad-band domains was derived from temporo-occipital records. Ten malnourished infants (5 - 23 months), age and sex-matched with 10 healthy controls (CON), having no neurological involvement or previous malnutrition, were studied. The malnourished group was tested on admission (ADM) and on discharge (DIS) from hospital. A stronger mean peak response to photic driving for the narrow band spectra was observed for the malnourished group, but this difference did not attain a level of statistical significance. This observation indicates a reduced efficacy of inhibitory processes in the malnourished brain, a condition also observed in the brain of malnourished animals. Significant differences were, however, found in the alpha-1 band for the undriven EEG, and in the summed alpha/beta-1 power ratio while driving at 8 Hz, between the malnourished and control groups. ADM and DIS groups did not differ significantly in the trend towards reduction from ADM to DIS to CON. These findings indicate that, in malnutrition (1) EEG measures can index the deviation of brain function from normality, and (2) physical properties relating to brain function remain abnormal despite anthropometric catch-up (AU)
Asunto(s)
Humanos , Lactante , Electroencefalografía , Cerebro/fisiopatología , Trastornos de la Nutrición del Lactante/fisiopatología , JamaicaRESUMEN
A central component of the primary health care approach in developing countries has been the development and utilization of community-based health workers (CHWs) within the national health system. While the use of these front line workers has the potential to positively influence health behavior and health status in rural communities, there continues to be challenges to effective implementation of CHW programs. Reports of high turnover rates, absenteeism, poor quality of work, and low morale among CHWs have often been associated with weak organizational and managerial capacity of government health systems. However, no systematic research has examined the contribution of work-related factors to CHW job performance. The research reported in this paper examines the relative influence of reward and feedback factors associated with the community compared to those associated with the health system on the performance of CHWs. The data are drawn from a broader study of health promoters (CHWs) conducted in two departments (provinces) in Colombia in 1986. The research was based on a theoretical model of worker performance that focuses on job related sources of rewards and feedback. A survey research design was employed to obtain information from a random sample of rural health promoters (N = 179) and their auxiliary nurse supervisors about CHW performance and contributing factors. The findings indicate that feedback and rewards from the community have a greater influence on work performance (defined as degree of perceived goal attainment on job tasks) than do those stemming from the health system.(ABSTRACT TRUNCATED AT 250 WORDS)