Computer solutions for photosynthesis rates from a two pigment model

A kinetic model for a two pigment mechanism of photosynthesis based on observations made on the red alga Porphyridium cruentum is developed. The model supposes that different products are formed by chlorophyll and phycobilin pigments and that these products react to produce oxygen. The product of the chlorophyll reaction is also rapidly utilized for O(2) consumption both in light and in the dark. Rate equations based on the model reactions were derived and put into an analog computer. The effect of varying parameters on the time course curves for oxygen exchange resulting from the model was studied. Appropriate selection of parameters yielded computer curves which resembled fairly closely the oxygen exchange curves obtained using Porphyridium. The model showed the Emerson enhancement effect, chromatic transients, "respiratory stimulation," and other effects observed with live algae.

Sepsis in surgical wounds. Multiple regression analysis applied to records of post-operative hospital sepsis

The method of multi-regression analysis as applied to data which are classified in a non-metric manner is discussed, and a set of data relating the risk of post-operation sepsis to various factors is analysed in this way.

Age over 60, male sex, long duration of operation, incision over 6 in. long and the insertion of a drain in the wound are all found to be associated with increased risk of post-operative sepsis. Operations for appendicectomy and those on the gall bladder have a relatively high basic risk of developing sepsis while operations for gastrectomy or those on the thyroid, and probably thoracic operations, have a low basic risk. The substantial differences in the gross risk of post-operative sepsis associated with the operations performed in the different hospitals included in the analysis are shown to be almost entirely accounted for by differences in the operations performed in them.

The routine fitting of kinetic data to models: a mathematical formalism for digital computers

A mathematical formalism is presented for use with digital computers to permit the routine fitting of data to physical and mathematical models. Given a set of data, the mathematical equations describing a model, initial conditions for an experiment, and initial estimates for the values of model parameters, the computer program automatically proceeds to obtain a least squares fit of the data by an iterative adjustment of the values of the parameters. When the experimental measures are linear combinations of functions, the linear coefficients for a least squares fit may also be calculated. The values of both the parameters of the model and the coefficients for the sum of functions may be unknown independent variables, unknown dependent variables, or known constants. In the case of dependence, only linear dependencies are provided for in routine use. The computer program includes a number of subroutines, each one of which performs a special task. This permits flexibility in choosing various types of solutions and procedures. One subroutine, for example, handles linear differential equations, another, special non-linear functions, etc. The use of analytic or numerical solutions of equations is possible.

ADANSONIAN ANALYSIS AND DEOXYRIBONUCLEIC ACID BASE COMPOSITION OF SOME GRAM-NEGATIVE BACTERIA

Colwell, R. R. (Georgetown University, Washington, D.C.), and M. Mandel. Adansonian analysis and deoxyribonucleic acid base composition of some gram-negative bacteria. J. Bacteriol. 87:1412-1422. 1964.-The deoxyribonucleic acid (DNA) base compositions and S values for a minimum of 134 coded properties were determined for representative cultures of the genera Pseudomonas, Xanthomonas, Aeromonas, Vibrio, Aerobacter, Escherichia, Alcaligenes, and Flavobacterium. Those cultures having a high degree of similarity by the criterion of numerical taxonomy were found to have similar DNA base compositions. The relative affinities of clusters of cultures suggest taxonomic relations. Eleven species of Xanthomonas might be a single species, and V. metschnikovii was shown to be more closely related to enteric bacteria than to other vibrios which, in turn, were found to be like pseudomonads. Aeromonas was found to be intermediate in similarity to enterics and pseudomonads and divisible into at least two, but possibly three, species. F. aquatile was unlike any of the other organisms studied, and its DNA also differed greatly in composition from other representatives of the genus.

INVESTIGATION OF AN OPERATOR METHOD IN THE ANALYSIS OF BIOLOGICAL TRACER DATA

Some factors affecting the usefulness of a linear operator in the analysis of tracer data were evaluated. Application of the operator to a sum of two exponential components resulted in the separation of the rate constants with an accuracy of 10 to 15 per cent if they differed by a factor of at least 2 and the error in the data was about 2 per cent. A factor of 4 was necessary if the error in the data was 6 per cent, and of 6 if the error was 10 per cent. The ratio of amplitudes varied from near unity to equality with the ratio of rate constants. However, if the ratio of amplitudes was greater than the ratio of rate constants the method would not resolve the rate constants. Application of the operator to a sum of three exponential components was also considered.

METHODS FOR AUTOMATIC NUCLEOTIDE-SEQUENCE ANALYSIS. MULTICOMPONENT SPECTROPHOTOMETRIC ANALYSIS OF MIXTURES OF NUCLEIC ACID COMPONENTS BY A LEAST-SQUARES PROCEDURE

1. A theoretical analysis of the errors in multicomponent spectrophotometric analysis of nucleoside mixtures, by a least-squares procedure, has been made to obtain an expression for the error coefficient, relating the error in calculated concentration to the error in extinction measurements. 2. The error coefficients, which depend only on the ;library' of spectra used to fit the experimental curves, have been computed for a number of ;libraries' containing the following nucleosides found in s-RNA: adenosine, guanosine, cytidine, uridine, 5-ribosyluracil, 7-methylguanosine, 6-dimethylaminopurine riboside, 6-methylaminopurine riboside and thymine riboside. 3. The error coefficients have been used to determine the best conditions for maximum accuracy in the determination of the compositions of nucleoside mixtures. 4. Experimental determinations of the compositions of nucleoside mixtures have been made and the errors found to be consistent with those predicted by the theoretical analysis. 5. It has been demonstrated that, with certain precautions, the multicomponent spectrophotometric method described is suitable as a basis for automatic nucleotide-composition analysis of oligonucleotides containing nine nucleotides. Used in conjunction with continuous chromatography and flow chemical techniques, this method can be applied to the study of the sequence of s-RNA.

REINFORCEMENT SCHEDULE GENERATED BY AN ON-LINE DIGITAL COMPUTER

A LINC digital computer was used to generate an autoregressive schedule of reinforcement. On such a schedule the probability of reinforcement is a function of the similarity in duration of the intervals between successive responses. A detailed analysis of the data obtained from monkeys on this schedule demonstrated two distinct tendencies in their behavior: a tendency for periodic response and a tendency for serial dependence between successive interresponse times.

PUNCHED CARD PROGRAMMING AND RECORDING TECHNIQUES EMPLOYED IN THE AUTOMATION OF THE WATA

A system of punched card programming and recording of primate discrimination learning experiments is described to illustrate the application of these techniques to the automation of the discrete trial learning situation, allowing for punched card recording and subsequent digital computer data analyses without intermediate data reduction. The system was also designed to control several potential sources of variability inherent in the conventional WGTA testing mode, including 1) the subject's (S's) motivation to test on each trial, 2) S's attention to the stimuli, and 3) the rate of trial presentation so as to be more under S's control. Reliable techniques of punched card programming and recording are detailed.