Showing papers by "Hampshire College published in 1979"

Periphyton production in Fort River, Massachusetts

Abstract: SUMMARY The primary production and general ecology of a periphyton community of a New England, lowland stream were studied over a seventeen-month period Temperature, light, periphyton chlorophyll-α, and community structure were monitored regularly Seasonally distinct chlorophyll peaks coincided with the light maximum in early May, just prior to the appearance of leaves of riparian trees, and again in autumn after terrestrial leaf fall During midwinter, despite low light and temperature levels and high stream discharge, mean chlorophyll concentrations remained similar to summer values A mathematical expression relating periphyton photosynthesis per unit chlorophyll-α to temperature, light and periphyton density was established with submersible light-dark chambers in situ Survey data collected over the study period were employed in the empirical equation to estimate seasonal variations in periphyton primary production Weekly mean daily estimates of periphyton gross production ranged from < 01 g O2 m−2, during midwinter, to 65 g O2 m−2 during early May Estimated annual periphyton gross production and respiration were 058 and 127 kg O2 m−2, respectively Factors influencing seasonal variations of Fort River periphyton standing crop are discussed

Use of the “Acetylene blockage” technique for assaying denitrification in a salt marsh

Abstract: The “acetylene blockage” technique was evaluated for measurement of denitrification in salt-marsh sediments (near Halifax, Nova Scotia, Canada). N2O in the gas phase of closed Spartina alterniflora marsh-sediment systems was analyzed with use of a thermal conductivity gas chromatograph sensitive to approximately 0.1 nmoles ml-1 gas. No N2O was detected for unfertilized sediment samples taken through the growing season and incubated in sealed buckets with 10% C2H2. For sediment samples amended with nitrate and for enrichments, initial rates of N2O evolution were higher in the presence of 10% C2H2 than in the absence of C2H2, but after longterm incubation N2O was consumed in some samples containing C2H2 as well as in samples without C2H2. In addition, total gaseous nitrogen (N2 and N2O) production in the absence of C2H2 was higher than in the presence of C2H2. Acetylene appears to be an inconsistent inhibitor of N2O reduction in salt-marsh sediments. The usefulness of the acetylene-denitrification technique in this habitat is, therefore, questionable.

The lessened locus of feelings: a transformation in French physiology in the early nineteenth century.

Abstract: Physiology in France during the first quarter of the nineteenth century has been discussed in terms of methodology its novel or increased reliance on vivisectional experiments; reductionism its growing rapprochement with the physical sciences; philosophy its incorporation of assumptions from the philosophical system of ideology; and disciplinary structure the development and ascendancy of a uniquely physiological conept of function, free of the limits of an earlier dependency on anatomical deduction.' Here, the point of departure is

Mass drivers. 1: Electrical design

Abstract: A mass driver is an electrical device used to accelerate payloads of any material to a high velocity. Small vehicles (called buckets) containing superconducting coils carry the payloads. These buckets are accelerated by pulsed magnetic fields, timed by information on their position, and are guided by induced magnetic fields set up in a surrounding guideway. Upon reaching the correct velocity, the buckets release their payloads, then they are slowed for recirculation to be reused. A rationale is presented that leads to a relatively simple and near-optimum design, as well as basic programs for calculating acceleration. The transverse oscillation frequencies are found to be invariant to guideway transverse dimensions.

The Developmental Priority of the Evaluative Dimension in Perceptions of Nonverbal Cues

Abstract: Researchers who have attempted to map the basic structure of broad psychological domains (such as interpersonal behavior) have invariably pointed to the importance of the evaluative dimension. It was predicted that sensitivity to such a salient dimension would develop prior to sensitivity to other important but apparently weaker dimensions, such as dominance-submissiveness. The predicted developmental trend was supported in a study of nonverbal decoding. When judging pairs of emotional cues communicated by the face or body and by the tone of voice, younger subjects, compared to older ones, were more likely to notice discrepancies in the degree of expressed positivity than in the degree of expressed dominance.

Mass drivers. 2: Structural dynamics

Abstract: Various structural and dynamical problems related to both small-scale forces between the drive coils and within the bucket structure as well as the overall combined large-scale dynamical interaction of the bucket stream and MDRE (Mass Drive Reaction Engine) structure are examined. The large-scale dynamics appear weakly stable. Finally, MDRE operation in an inverse-square-law gravitational field is discussed and the required curved shape of the guideway is computed.