Biophysical interactions in tropical agroforestry systems

sequential systems, simultaneous systems Abstract. The rate and extent to which biophysical resources are captured and utilized by the components of an agroforestry system are determined by the nature and intensity of interac-tions between the components. The net effect of these interactions is often determined by the influence of the tree component on the other component(s) and/or on the overall system, and is expressed in terms of such quantifiable responses as soil fertility changes, microclimate modification, resource (water, nutrients, and light) availability and utilization, pest and disease incidence, and allelopathy. The paper reviews such manifestations of biophysical interactions in major simultaneous (e.g., hedgerow intercropping and trees on croplands) and sequential (e.g., planted tree fallows) agroforestry systems. In hedgerow intercropping (HI), the hedge/crop interactions are dominated by soil fertility improvement and competition for growth resources. Higher crop yields in HI than in sole cropping are noted mostly in inherently fertile soils in humid and subhumid tropics, and are caused by large fertility improvement relative to the effects of competition. But, yield increases are rare in semiarid tropics and infertile acid soils because fertility improvement does not offse

Psychic Changes following Myelography with Metrizamide and Iohexol : A comparative investigation with psychologic tests

Based upon the results of repeated psychologic tests, psychic impairment following myelography has been studied in 60 patients. Thirty of these had lumbar myelography with metrizamide and 30 with iohexol. Psychic impairment was noted in both groups, although with a higher frequency and much more marked in the group which had metrizamide myelography. For this type of examination iohexol is thus to be recommended

Psychologic Tests in the Evaluation of Psychic Changes after Myelography with Metrizamide

The possibility of using psychologic tests to demonstrate psychic changes following myelography with metrizamide was investigated in 15 patients. The tests were made before and after the examination. The results revealed psychic changes of cognitive nature to occur both at 6 and at 24 hours after myelography. Of the tests used determination of the reaction time gave most significant results. Subjectively the patients considered themselves better 24 hours after the examination than after 6 hours. This was not confirmed from the test results—an observation indicating the sensitivity of the test instruments used. Thus, these appear to be well suited to study cognitive changes caused by the contrast media used in this particular type of examination. Since the tests are repeatedly performed, the effect of habituation and of learning cannot be avoided. However, when applied in groups of patients, in whom the effects of different contrast media are compared, the disadvantages of these specific effects can be neglected