16,498 research outputs found

    Thermocouple installation

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    A thermocouple assembly which includes a plug having a pair of small diameter holes near one end thereof which are spaced a small distance apart to leave a thin quantity of plug material between the holes is presented. There are a pair of thermocouple wires extending through the different holes and with the outer ends of the wires joined to the thin quantity of plug material which lies between the holes to form a thermocouple junction

    Determination of amino acids and nitrates in soils: amino acids, ammonia and nitrates in manured and limed soil

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    In view of the fact that no data had ever been obtained on the quantitative relationships of the organic material in the soil by such methods as would preclude a chemical transformation, two things seemed desirable, in continuing the humus investigations at the Iowa Agricultural Experiment Station. First, to attempt the analysis of the organic material of the soil without subjecting it to hydrolysis or other chemical change, and second, to correlate the proportionate quantities of the compounds or classes of compounds found with the kind of soil, its history, treatment, fertility, etc

    Carbon dioxide production in soils and carbon and nitrogen changes in soils variously treated

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    The carbon dioxide of the soil atmosphere, along with the water, has long been recognized as the most active agent in the decomposition of comparatively inert minerals to give available and soluble plant food material. It is probable that herein lies the great benefit which comes from the application to soil of organic material which not only increases the energy material easily available for the bacteria, but also improves the physical condition of the soil. This in turn increases bacterial activity, which gives rise to increased carbon dioxide production. At the Iowa Agricultural Experiment Station, for some time past, both in the laboratory and in the field, determinations have been made of the carbon dioxide of the soil atmosphere or of the carbon dioxide evolved by soils. These experiments have been carried out with the primary object of obtaining information as to the rate of decomposition of the soil or of organic matter added to the soil, under various conditions and treatments. In this paper attention will be confined mainly to the production of carbon dioxide by soils and its measurement. Little will be said concerning its effectiveness as an agent for rendering plant foods available

    The determination of ammonia in soils

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    Theoretically, the ideal method for determining ammonia in soils would give the absolute amount of ammonia present as such and as the ammonium radical, but in the light of present knowledge, it cannot be said beyond all doubt that any conceivable method would give this ideal result. This is true because a large part of the nitrogen of the soil is present in protein and protein degradation products, the extensive decomposition of which gives large amounts of ammonia. The uncertainty regarding just what products are present does not permit the finding of conditions which we can be certain will expel ammonia already present and not decompose any material to give, among other products, ammonia. The problem is further complicated by the well known absorptive and adsorptive powers of the soil

    Magnetorotational-type instability in Couette-Taylor flow of a viscoelastic polymer liquid

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    We describe an instability of viscoelastic Couette-Taylor flow that is directly analogous to the magnetorotational instability (MRI) in astrophysical magnetohydrodynamics, with polymer molecules playing the role of magnetic field lines. By determining the conditions required for the onset of instability and the properties of the preferred modes, we distinguish it from the centrifugal and elastic instabilities studied previously. Experimental demonstration and investigation should be much easier for the viscoelastic instability than for the MRI in a liquid metal. The analogy holds with the case of a predominantly toroidal magnetic field such as is expected in an accretion disk and it may be possible to access a turbulent regime in which many modes are unstable.Comment: 4 pages, 4 figures, to be published in Physical Review Letter

    Affective bias and current, past and future adolescent depression: A familial high risk study.

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    Affective bias is a common feature of depressive disorder. However, a lack of longitudinal studies means that the temporal relationship between affective bias and depression is not well understood. One group where studies of affective bias may be particularly warranted is the adolescent offspring of depressed parents, given observations of high rates of depression and a severe and impairing course of disorder in this group
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