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A deterministic structure imitating a sediment yield model should mathematically approximate the behavior of two distinct phases of the phenomenon, the upland phase and the lowland channel phase. For upland erosion, research is most needed in quantifying gully erosion, whereas for lowland streams it is most needed to explain the influence of meanders on bed material transport and to develop a floodplain accounting component. In both phases, research is needed to explain the effects of unsteadiness and flow nonuniformities on transport. Sensitivity analysis studies of sediment yield models are needed to illustrate how well the models can be calibrated and what output precision can be expected from input data with known statistical characteristics. Present estimates indicate that although a regression of annual sediment discharge on annual water discharge might be expected to give a prediction within 20% of the observed value, even a well-calibrated digital model might give an error greater than 40% for a single storm on a small watershed.

D-[3H]LSD binds saturably, reversibly, and with a high affinity (KD = 10 nM) to rat brain membranes. The association and dissociation rates of binding are temperature dependent and fastest at 37 degrees C. Binding is enriched in crude microsomal (P3) membranes. D-[3H]LSD binding is stereospecific as L-LSD, the psychotropically inactive enatiomer, is 1000 times weaker than D-LSD as a displacing agent. The potencies of other LSD analogues parallel their psychotropic activity with the exception of 2-bromo-LSD (psychotropically inactive) which is as potent as D-LSD in displacing bound D-[3H]LSD. Serotonin is the only putative neurotransmitter with affinity (ED50 = 3 muM) for the LSD binding site, and psychotropically active alkylindoleamines are also potent displacing agents. Destruction of presynaptic serotonin neuronal elements by lesioning the midbrain raphe nuclei does not chang the affinity or maximum number of detectable in vitro D-[3H]LSD bindind sites. The regional distribution in monkey brain of D-[3H]LSD binding and high affinity [3h]serotonin uptake, a marker for pre-synaptic serotonin nerve terminal density, shows some correlation. The most notable exceptions are cerebral cortical areas which are highest in D-[3H]LSD binding and only intermediate in [3h]serotonin uptake. Our evidence suggests that D-[3H]LSD binds to post-synaptic serotonin receptors.

In terms of its response to biochemical oxygen demand (BOD) and dissolved oxygen (DO) inputs, a natural waterway may be treated as a system governed by the BOD and DO balance differential equations. Using the response of the DO balance differential equation to impulse inputs of DO and BOD, one can compute by convolution the response of the system to arbitrary BOD and DO inputs. The convolution technique requires numerical integration, but it is not a numerical solution to a differential equation; it therefore avoids the stability problems inherent in such solutions. The convolution technique permits consideration of longitudinal dispersion in systems that have time varying DO and BOD inputs, a situation that could previously be investigated only by numerical solutions to the basic differential equations. Examples show the capability of the convolution technique to reproduce field data and to match previously developed analytical and numerical techniques.

A survey of recent literature on the effects of low levels of air pollutants on plants, and the results of our experiments with low levels of ozone (

1. 1. The distribution of biogenic amines in Schistosoma mansoni was studied by the use of the histochemical fluorescence technique of Falck & Owman (1965). 2. 2. Catecholamines were found in the central ganglia, the nerve trunks, and in a network of fibers emerging from the nerve trunks and distributed throughout the parenchyma of the worm. 3. 3. 5-Hydroxytryptamine has been localized in the head region near the commissure, in the vicinity of the nerve trunks, and in small granules throughout the parenchyma of the worm. 4. 4. Preincubation of the worms with 5-hydroxytryptophan and iproniazid resulted in a tenfold increase in the levels of 5-hydroxytryptamine and in the appearance of a larger number of 5-hydroxytryptamine containing structures. 5. 5. The fluorescence characteristics, determined by two different methods, and the Chromatographic behaviour of the tryptamine-like material extracted from schistosomes were identical with that of 5-hydroxytryptamine.

Two factors prevent the direct determination of the point spectrum of axial turbulence from a spectrum of the fluctuations in rpm values of the analog output of a rotary flow meter. The first of these is the effect of the finite size of the flow meter propeller, the second is the effect of its inertia. The finite size effect depends on the local turbulence structure and is characterized by an "efficiency factor" which in general can only be estimated. The effect of propeller inertia can be evaluated by linearizing the equation of motion of the propeller. From the resulting linear ordinary differential equation with constant coefficients, a transfer function for the linear system can be calculated. This transfer function makes it possible to calculate a spectrum of axial turbulence in which the velocity is averaged over the area of the propeller. Experiments in which propellers were oscillated sinusoidally while being towed through still water showed that the amplitude response function is approximately equal to that of a first-order system, while the phase function appeared to be independent of the natural frequency of the system.

The sampling system collects water-sediment samples at local stream velocity from any point in an open channel flow. The system uses a flow-through Pitot tube as a combination velocity sensor and sampler nozzle. The main advantage of the sampling system over existing suspended sediment samplers such as the US-P series samplers is that a sample of any desired volume can be collected without changing the position of the sampler nozzle. To compare the performance of the system with that of other samplers, suspended-sediment samples were collected from a flat-bed flow using the system, a US DH-48 sampler modified for point sampling, and a siphon sampler. On the basis of these samples, at the 99% confidence level, the relative percent difference between the concentrations of the samples from the system and the siphon sampler was between -5.45 and 4.45 and the relative percent difference between the concentrations of the samples from the system and from the US DH-48 was between -0.54 and 7.78.

Subcellular fractionation of rat spinal cord on continuous sucrose density gradients provides evidence for the existence of a specific synaptosomal fraction (enriched in pinched-off nerve endings) that accumulates glycine selectively by way of a high-affinity transport system. The particles in this fraction sediment to a less-dense portion of sucrose gradients than do particles that accumulate neutral, basic, aromatic, and acidic amino acids. Particles accumulating γ-aminobutyric acid are even less-dense than those storing exogenous glycine. The glycine-specific synaptosomal fraction also exists in the brain stem but not in the cerebral cortex. These findings provide neurochemical support for the suggestion that glycine has a specialized synaptic function, perhaps as neurotransmitter, in mammalian spinal cord.

Publisher Summary This chapter discusses the neurochemical correlates of synaptically active amino acids. An abundance of evidence indicates that the high affinity uptake systems for glycine and glutamic and aspartic acids label unique populations of nerve terminals in which these substances may serve a neurotransmitter role. The initial experiments on amino acid uptake employed relatively crude homogenate systems which can be prepared more rapidly than purified synaptosomes. It is found that these preparations cannot be washed as they contain enough endogenous concentrations of the amino acids that one cannot reliably study the uptake of lower than 10 μM concentration of radioactive amino acid. The serotonin precursor, L-tryptophan, apparently is accumulated into rat synaptosomes by a high-affinity system, and using purified synaptosomes others reported high affinity accumulation of leucine into the cerebral cortex. Accordingly, one can reexamine the accumulation of numerous amino acids by purified preparations of synaptosomes, focusing on concentrations between 1 and 10 μM. For all amino acids studied in the cerebral cortex, with the exception of glycine, one can demonstrate high affinity synaptosomal uptake.

Publisher Summary This chapter discusses the neurochemical correlates of synaptically active amino acids. An abundance of evidence indicates that the high affinity uptake systems for glycine and glutamic and aspartic acids label unique populations of nerve terminals in which these substances may serve a neurotransmitter role. The initial experiments on amino acid uptake employed relatively crude homogenate systems which can be prepared more rapidly than purified synaptosomes. It is found that these preparations cannot be washed as they contain enough endogenous concentrations of the amino acids that one cannot reliably study the uptake of lower than 10 μM concentration of radioactive amino acid. The serotonin precursor, L-tryptophan, apparently is accumulated into rat synaptosomes by a high-affinity system, and using purified synaptosomes others reported high affinity accumulation of leucine into the cerebral cortex. Accordingly, one can reexamine the accumulation of numerous amino acids by purified preparations of synaptosomes, focusing on concentrations between 1 and 10 μM. For all amino acids studied in the cerebral cortex, with the exception of glycine, one can demonstrate high affinity synaptosomal uptake.

—The accumulation by synaptosomal fractions from rat central nervous system tissue of transmitter candidate amino acids and non-candidate amino acids was studied with respect to ionic requirements, metabolic inhibitors, structural analogues, and ontogeny. For l-glutamic and l-aspartic acids in cortex and spinal cord and glycine in spinal cord a stringent sodium requirement for high affinity uptake was demonstrated. Detailed kinetic analysis of the sodium requirement for glutamic acid uptake into cortical synaptosomal fractions suggests that: (1) sodium ion acts both competitively and non-competitively in determining the velocity of high affinity uptake; (2) in the absence of sodium ion only the low affinity uptake can be demonstrated; and (3) inhibition of the Na–K-ATPase enzyme system with ouabain reduces the velocity of uptake to 60% of control values in contrast to alanine whose synaptosomal uptake is less dependent on this enzyme system. No potent inhibitors of l-glutamic acid accumulation were found among several structural analogues or derivatives. The kinetic analysis for glycine accumulation was more complex and suggested allosteric interactions between glycine and sodium ion. Developmental studies revealed GABA and l-glutamic acid to have absolute sodium requirements for cortical synaptosomal accumulation from the 16th gestational day through adulthood, with glycine accumulation showing a decreasing sodium requirement as maturation proceeded over this period. The combined evidence suggests that sodium requirement for high affinity uptake is a characteristic of neuroactive substances and may be used as a screening tool to search for other neurotransmitter candidates.

Most neurotransmitters, except for acetylcholine, possess high affinity neuronal uptakes. With reasonably well established transmitter candidates such as catecholamines, serotonin and GABA, these uptake systems are studied with a view to characterizing the synaptic behavior of the transmitter in question. With more questionable transmitter candidates, such as the amino acids, before characterizing subtleties of their synaptic activities, it is crucial first to determine whether they are in fact neurotransmitters. In our laboratory, uptake studies have been employed to adduce evidence in support of certain amino acids as transmitters. Specifically, we have compared the synaptosomal accumulation of numerous amino acids and found that unlike most amino acids, glutamic and aspartic acids and glycine (in the spinal cord and brain stem) are transported by unique high affinity systems into distinct populations of synaptosomes. In this way neuronal uptake has provided powerful biochemical support for the proposition that these compounds are neurotransmitters in the mammalian central nervous system.

An examination is made of the political and potentially conflicting implications of the current global predicament with regard to population growth, finite resources, and the negative environmental influence of technological development. The problem is borken down and discussed in the following manner: 1) the international implications of population dynamics, resource constraints and distribution, and technological developments; 2) the interdependencies and reverberating effects associated with efforts to cope with any one dimension singly; and 3) the ways by which the conduct of research in the academic community can address itself more clearly to environmental problems. A prime objective is to highlight the implications for the developed as well as the less developed world. Thus, the empirical analysis centers around Japan, the People's Republic of China, the Soviet Union, and the U.S.

In the controversy in the empirical literature, writers such as Eisner and Strotz focus attention on the acceleration principle and present empirical evidence that investment is determined primarily by some relationship of product demand to existing capacity. Little evidence is presented about the influence of financial variables on investment, while the need for cost reduction as a determinant of investment is seldom discussed.1 On the other hand, writers such as Meyer, Kuh, and Anderson, specifically emphasizing the interrelationships of the marginal efficiency and marginal cost of funds schedules, have presented evidence that numerous factors influence investment decisions, and that changing economic conditions affect the relative importance of each of the factors.2