The spectral properties of plant leaves and stems have been obtained for ultraviolet, visible, and infrared frequencies. The spectral reflectance, transmittance, and absorptance for certain plants is given. The mechanism by which radiant energy interacts with a leaf is discussed, including the presence of plant pigments. Examples are given concerning the amount of absorbed solar radiation for clear sky and overcast conditions. The spectral properties of desert plants are compared with those of more mesic plants. The evolution of the spectral properties of plant leaves during the early growing season is given as well as the colorimetric behavior during the autumn.

A set of fi ve spec ia lly selected colored-glass fil ters to identify va ri a bles of m a lfun ction of photoelectri c recordin g spectrop hoto lTl.ctcrs cq uipped wit h tristim ulus integrators have been standa rdi zed on a number of spectrop hoto meters corrected for all known errors (wavelen gth, ze ro, 100 p ercen t, sli t-w idth , ine rt ia, bac k-reflectance, and stray-energy). T o these standardi zed spectrop hoto metric d ata de fi nite a moun ts of t hese errors were deliberately introdu ced and co nve rted to t ri stimulus va lues a nd chromaticity coordinates of the International Com m ission of Illumin ation syste m of colorimetry for So urces A, E , a nd C. Simila r r eductions s how t he effects of slit widt hs of 1, 5, 10, a nd 15 millimi crons (nw) on compu ted r es ults both by t he selected-ordin ate method of 10, 30 , a nd 100 ordin ates, a nd by t he we ighted-ordinate met hods of 1-, 5-, 10-, a nd 15-ml" in ter vals. Duplicate se ts of these glasses have been evaluated by visual co mpa ri so n w it h t his set of m aster standards, and a re availa ble as pa rt of t he Stand ard M a teri a ls P rogra m of the N atio nal B ureau of Standa rds. By co mpa ring t he ce rt ified values of lumin ous tra nsmi ttance a nd chro maticity coord inates for a set of t hese glasses wi t h t he values obtained on a par ticular in teg rator-spectrop hotometer co mbinatio n, t he type an d extent of instru mental errors ma.v be evaluated .

No abstract

Contract No* 33 (6l6) £2-21. It is coordinated with Air Force Contract No. 33 (6l6) -262 under Dr. High T. O'Neill O'Neill Associates, Annapolis, Maryland, who requested the NBS to perform this year-long test of leaves of white oak trees.

A spec trophotome trie and colorimetric study has been made on the leaves of three species of trees (Beech, Dogwood, and White Oak), one shrub (Mountain Laurel) and one herb (Milkweed), stored in metal containers with tightly fitting metal covers for intervals of 1? hours to 12 days. This was done to determine the color variations that occur in these representative types of foliage during storage, and to predict if possible, the color variations that may occur in similar and otter types of foliage during periods of shipment in similar covered metal containers. Contents Page I.

In 1934, Gibson, Walker, and Brown developed sets of four colored glass filters to serve as working standards of spectral transmittance for checking the reliability of spectrophotometers. Several sets of these glasses were measured carefully and reserved and designated as future reference standards. Duplicate standards evaluated by comparison with the reference standards are available by purchase to the public. The current set of reference standards was established in the years 1945 to 1947, and one of these reference standards (selenium-red) was recalibrated in 1952. This paper reports a recalibration, made in 1961 and 1962, of all four glasses (selenium-red, carbon-yellow, copper-green, cobalt-blue) on three spectrophotometers (Cary 14, Beckman DU, König-Martens). Except for the cobalt-blue standard, the values of spectral transmittance found differ from those previously assigned by amounts differing at some wavelengths by as much as or slightly more than the uncertainties estimated for the present values, though not by amounts exceeding the combined uncertainties of the present and previous determinations. The indicated changes for these three standards are fairly regular, however, and support the view that the selenium-red and carbon-yellow standards are changing chiefly by formation of a reflectance-reducing film on the surfaces. The indicated rate of upward drift is slow, and suggests that it takes about 10 years for the drift to exceed the assigned uncertainity.

One can define the safeguards system for nuclear material as the set of all protective actions taken to prevent or to deter attempts to divert nuclear material to unauthorized use" Maintenance of effective safeguards requires a program for routine assessment of plant safeguards systems in terms of their capabilities to satisfy safeguards aims. Plant internal control systems provide capabilities for detection of unprevented diversion and can provide assurance that diversion has not occurred. A procedure called Diversion Path Analysis (DPA) enables routine assessment of the capabilities of internal control systems in this regard and identification of safeguards problem areas in a plant. A framework for safeguards system design is also provided which will allow flexibility to accommodate individual plant circumstances while maintaining acceptable diversion detection capability. The steps of the procedure are described and the practicality of the analytical method is shown by referring to a demonstration test for a high throughput process where plant personnel were major participants. The boundary conditions for the demonstration case are given, along with some conclusions about the general procedure.

A spec trophotome trie and colorimetric study was made of the permanence of these color standards kept in dark storage and of the fading of these standards when exposed behind glass to natural North skylight and South sunlight for periods of two and of ten months. Measurements of spectral directional reflectance were made for the visible spectrum I 4 OO to 750 millimicrons for each of these seven conditions of storage or of time of exposures.