Color sensitivity

This paper reports primarily upon tests of the color sense of about thirty men who have had large experience in the color grading of vegetable oils in terms of Lovibond glasses, nearly all of these men being members of the American Oil Chemists’ Society. Similar tests on five other observers are also included for comparison. All of the oil chemists were first tested by the Stilling Chart test, but the results by this test (although reported) are not the principal matter of interest. This test was regarded merely as preliminary, serving to discover any gross abnormality of color sense. The tests of specific interest relate to the observer’s ability to report correctly very small differences in Lovibond red at 35 yellow 7.6 red on the Lovibond scale, brightness diffences being eliminated so that the judgment depends, in effect, entirely upon the observer’s sensibility to difference in dominant wave length at equal brightness. The subject’s ability in this regard was tested by the well known psycho-physical method of “right and wrong answers.” The results for each observer are expressed so as to show the probability of his perceiving correctly given small differences in Lovibond red, under certain specified conditions. The chief results may be summarized as follows:

1. 1.
   A difference of 0.1 red at 35 yellow 7.6 red is perceivedwith certainty by only very few exceptional observers. However, this difference is perceptible in the sense that its presence does affect the observer’s judgmentin the average, although he is very doubtful of the reality of such a difference.     

The recovery of distorted bandlimited almost-periodic signals

It is shown that thePQ theorem can be used to solve a certain signal recovery problem in which the transmitted and received signals are almost periodic functions. In this problem the signal to be recovered, which is bandlimited, is nonlinearly distorted and then bandlimited to the original band. Related signal recovery results are also given. These related results, unlike thePQ theorem, are applicable in settings in which the underlying signal space is not a Hilbert space or even a space that is complete.     

Evolution of cavity size distributions in dual-ion irradiated austenitic stainless steel and Fe-Cr-Ni ternary alloys

The first four moments of experimentally measured cavity size distributions in dual-ion irradiated 304SS, Fe-12Ni-15Cr and Fe-30Ni-15Cr alloys have been calculated for a range of fluences, helium injection rates, and irradiation temperatures. The moments are shown to correctly describe the effects of alloy composition, fluence, helium and temperature on the evolution of the cavity size distributions. Experimentally determined moments are compared with those calculated from cavity nucleation and growth theories. The moments reflect the competition between nucleation and growth processes and provide insight into the details of the transient low swelling regime.     

Isotope Studies of the CMR Compounds La1−xCaxMnO3+δ

Oxygen isotope effect studies of the ferromagnetic Curie temperature T _c of La_1?x Ca _x MnO₃ are presented. The isotope exponent α₀=?ΔlnT _c/Δlnm ₀ changes from 0.4 to 0.14 in the range 0.2<x<0.43. The isotope exponent decreases strongly with increasing tolerance factor, or decreasing lattice distortion. Above Tc the conductivity is characteristic of small polarons. Raman scattering shows a prominent peak at 230 cm?1. The peak width could be related to site-dependent Jahn–Teller distortions above T _c, becoming significantly smaller at and below T _c. IR reflectivity data show a much larger zero frequency IR conductivity than dc conductivity. The IR peaks are independent of temperature between 150 and 295 K.     

Decay of the HO2 and O−2 Radicals Catalyzed by Superoxide Dismutase. A Pulse Radiolytic Investigation

The pulse radiolysis technique has been employed in the investigation of the dismutation of superoxide radicals, O^?₂ and HO₂, in the presence of superoxide dismutase in aqueous solutions. The decay of superoxide radicals in the presence of the enzyme was found to be first order in both enzyme and superoxide concentrations. An apparent second order reaction rate constant was found to be about 2 × 10⁹ M^?1 sec^?1, decreasing slightly as the pH is increased from 5 to 9.5. A mechanism which accounts for all our observations is proposed. It includes two steps: (1) formation of a product (EO^?₂ or E^?) from one enzyme (E) molecule and one O^?₂ radical ion; (2) regeneration of E by a reaction of this product with an additional O^?₂ ion radical. The reaction rate constants k = (1.4 ± 0.2) × 10⁹ and k = (1.9 ± 0.6) × 10⁹ M^?1 sec^?1 were measured at pH = 7 in an oxygenated 0.16 M sodium formate solution.     

A Note on BIBO Stability of Linear Discrete-Space Systems

The cornerstone of the theory of discrete-space single-input single-output linear systems is the idea that every such system has an input-output map H that can be represented by a convolution or the familiar generalization of a convolution. This thinking involves an oversight which, under some mild assumptions, was recently corrected by adding an additional term to the representation. Here we give a criterion for the bounded-input bounded-output stability of such systems.     

Transmission electron microscope specimen preparation of Zn powders using the focused ion beam lift-out technique

Particles of Zn powder have been studied to show that high-quality scanning electron microscope (SEM) and transmission electron microscope (TEM) specimens can be rapidly produced from a site-specific region on a chosen particle by the focused ion beam (FIB) lift-out technique. A TEM specimen approximately 20-μm long by 5-μm wide was milled to electron transparency, extracted from the bulk particle, and micromanipulated onto a carbon coated copper mesh TEM grid. Using the FIB lift-out method, we were able to prepare a site-specific TEM specimen from a difficult material in under 3 hours. The TEM analysis of the lift-out specimen revealed a large amount of thin area free from characteristic signs of damage that may be observed as a result of conventional argon ion milling. The overall microstructure of the specimen prepared by the FIB lift-out method was consistent with samples prepared by conventional metallographic methods. A grain size of ∼10 to 20 μm was observed in all specimens by both TEM and SEM analysis. Light optical microscopy revealed the presence of internal voids in ∼10 to 20 pct of all particles. The SEM analysis showed the voids to extend over ∼70 pct of the particle volume in some cases.