Towards a classification of organic enrichment in marine sediments based on biogeochemical indicators.

A nomogram is developed to show that pH, redox potentials (Eh(NHE)) and measures of dissolved sulfides (H2S + HS(-) + S(2-))(total free S(2-)) can be used to classify organic enrichment impacts in marine sediments. The biogeochemical cycle of sulfur in marine sediments is described to show that changes in macrobenthic infauna community structure associated with high levels of organic matter supply result from stress due to oxygen deficiency (hypoxia and anoxia) and toxic effects of S(2-). The changes reflect enhancement of microbial sulfate reduction under conditions of high organic matter sedimentation and the progressive formation of hypoxic-anoxic conditions measured by decreased Eh NHE and increased concentrations of S(2-). The nomogram provides a basis for classification of the oxic status of marine sediments based on changes in inter-related biological and biogeochemical variables along an organic enrichment gradient.

Attention in direct and indirect memory tasks with short- and long-term probes.

In two experiments, college students verified the answers to addition problems as their primary task while simultaneously viewing a word or nonword. The degree of attention allocated to the verbal stimulus varied depending on the difficulty of the problem and the instructions given. After each problem, a test probe assessed either a direct test of recognition memory or an indirect test of repetition priming in lexical decision at lags of 0, 1, or 8 intervening trials. The degree of attention at encoding and lag strongly affected recognition sensitivity (d'), but only lag affected recognition latencies. The repetition-priming effect neither declined with lag nor varied with the degree of attention. The degree of attention at encoding thus affects direct and indirect test performance differentially, a finding consistent with the distinction between explicit and implicit systems of long-term memory.

Effects of 4 beta-adrenoceptor blocking drugs on blood pressure and exercise heart rate in hypertension.

The effects of 4 beta-adrenoceptor blocking drugs on blood pressure and on exercise tachycardia were compared in a within-patient study of patients with uncomplicated essential hypertension. Twelve patients were treated with propranolol, practolol and atenolol and 7 of the same patients also received oxprenolol. Each patient received each drug separately, withdrawing each drug before starting the next, and each patient was titrated to the lowest attainable blood pressure and heart rate with each compound. All 4 drugs caused reductions in both systolic and diastolic blood pressure and in the heart rate induced by exercise. The maximum reduction by each drug in both systolic and diastolic blood pressure was the same. There were small but significant differences in the effects on heart rate between those drugs which had intrinsic sympathomimetic activity and those which did not have this property.