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A graph paper on which a Gaussian function of unit amplitude appears as a straight line was produced in an attempt to devise a method which would combine the obvious advantages of a linear presentation with the improved definition and convenience of a differential plot. A semilogarithmic plot of the linear differential pulseheight spectrum of 622 kev gamma ray from a Cs137 source is given as an example of the technique. The method requires only the data points from the multichannel analyzer and an estimate of the maximum height of the photopeak above background. Gaussian plots proved convenient checks on instrumental reliability; amplifier nonlinearity or drift cause noticeable deviations from linearity. (P.C.H.)

The electromagnetic boundary value problem of two waveguides coupled by an aperture or an aperture in a waveguide radiating into free space may be described by an integral equation. An analytical solution to this integral equation cannot be readily found due to the complexity of the kernel. However, extremely useful results may be obtained if the method of moments is employed to reduce the integral equation to a matrix equation which can be solved by known methods. In this short paper, series and shunt slots in a rectangular waveguide are analyzed using this technique.

An easier way for students to draw families of conics.

The conditions for the production of paper pulp from rice straw by the alkali process have been investigated. About 22% of soda on the weight of the straw used in 3% solution, a temperature of 100–05°C. and a cooking period of 3 hours have been found to be satisfactory. With a view to effect economy in alkali the mother liquor has been used in a subsequent double boiling process yielding paper pulp of good quality. In a straw having cellulose (Cross and Bevan) 37·5% the yield of paper pulp is about 44%. The characteristics of the pulp are described in detail.

IN paper chromatography, the RF value, or ratio of distance travelled by substance to the distance travelled by solvent front, is generally used as the criterion of identity. If two substances have the same RF values in two or more solvent systems, they are assumed to be identical. But although RF values are often quoted with great precision, experience shows that they are, at best, only a rough guide and should not be used as the sole means of identifying a substance.

The thin-layer chromatographic properties of twenty-seven commercially available di- and tripeptides and fourteen constituent amino acids in five different solvent systems on thin-layers of cellulose are reported. Theoretical R F values determined using the equation of P ardee are compared with the observed R F values and found in many cases to give wide differences. New empirical relationships for calculating the R F values of small peptides from the R F values of the constituent amino acids are proposed. The relationships are based on the additivity of R F values and are valid for both thin-layer and paper chromatography. It is shown that R F values determined using these new equations agree more closely with the observed and reported R F values than does the P ardee equation.

A part of the dye-protein complex formed in paper electropherograms of blood sera cannot be eluted from sections of the electropherograms by heating the sections with a N hydrochloric acid at 100°C. However, the noneluted part of the dye-protein complex may be calculated by assuming that it is adsorbed by the paper and therefore by applying the Langmuir isotherm equation.

A commercial reagent-impregnated paper strip test for the determination of production of niacin by mycobacteria has been evaluated. Safety, simplicity, uniformity, and stability were found to be inherent features of the test strips. Results compare favorably with those obtained using the Konno test as modified by Runyon and associates. Precautions which must be observed in performing this determination are listed.

A modification of the EEL Scanner is described which makes allowance for deviations from Beer's Law. An account is given of the methods used to establish the reliability of the results obtained, and some of the possible sources of error are mentioned.

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Lüzuci, sıkıştınlamaz ve homogen bir akışkanın hareket dife- rensiyel denklemleri lineer değildirler* Bu yüzden onların genel çözümlerini bulmak çok güç ve hattâ imkânsızdır. Araştırıcılar ya özel tarzda çözümler bulmakla iktifa ederler veya çözümü sadeleştirici bazı kabuller yaparlar.

A number of Cepheid variables in the small and in the large Magellanic cloud are analysed. The light curves used are those published by H. Shapley and his associates.

FOR quantitative determinations of amino-acids separated on filter paper, it is often desirable that the spots should contain a larger quantity of substance than is as a rule possible to achieve with unaffected resolution. A one-dimensional technique in which the substance to be analysed is applied along a line across the paper has been described by Yanofsky, Wasserman and Bonner1. I have successfully applied the following two-dimensional technique for separating comparatively large quantities of amino-acids in bacterial hydrolysates.