[A statistical method for the determination of the yield correlation of antibiotic-producing microorganisms].
The antibiotic yields of industrial selectants must be checked at several steps of cultivation. Here the question arises whether the activities at the different levels of cultivation are correlated. The common coefficient of correlation cannot be used because repeated determinations of the yield at one selectant result in different values. In order to have only one fixed value per selectant we define the mean value around which the observed values are varying. But these mean values cannot be observed. Thus, an adequate method of correlation similar to that in Guiard and Herrendörfer (1977) was used. The method is demonstrated in two examples: With selectants of Streptomyces noursei for streptothricin titers in 20 ml- and 20 l-cultures as well as with selectants of Penicillium chrysogenum for potency indices in surface cultures and penicillin titers in 50 ml submerged cultures, respectively. In both cases the coefficients of correlation were above 0.7.
[Use of automated image analysis for screening the efficiency of turimycin-producing Streptomyces strains].
The growth of the surface colonies on solid media is studied with the image analyzing system Quantimet 720 M controlled by a PDP 11 computer. For the bacterial strain Streptomyces hygroscopicus JA 6599 a new differential equation describing the kinetic behaviour of the area of the colony is suggested. It is shown that this time dependence of area describes more realistically the experiment than the function resulting from Pirt's model. Two new constants arise from the growing curve, alpha describes the profile of density of the colony and k0 is correlated to the growing constant of the colony. Both parameters can be correlated to the amount of antibiotics produced and, therefore, it is possible to use this information for the selection procedure of the colonies. A uniform criterion for selection was found for each colony of two mutants of the turimycin-producing strain Streptomyces hygroscopicus JA 6599, which reads: (Formula: see text). The quality of the selection criterion of surface colonies with higher productivity is dependent on the mean value of the growing parameters of all colonies under investigation. Limitations of the selection method arise from the need for great uniformity of environmental conditions, growth medium and a homogeneous spore suspension, which have to consist of a large amount of single spores in order to assure a reproducible growing curve of the colonies. For the last condition a special technique is pointed out.
Hedy: A Gradual Language for Programming Education
One of the aspects of programming that learners often struggle with is the syntax of programming languages: remembering the right commands to use and combining those into a working program. Prior research demonstrated that students submit source code with syntax errors in 73% of cases and even the best students do so in 50% of cases. An analysis of 37 million compilations by 250.000 students found that the most common error was a syntax error, which occurred in almost 800.000 compilations. It was also found that Java and Perl are not easier to understand than a programming language with randomly generated keywords, stressing the difficulties that novices face in understanding syntax. This paper presents Hedy: a new way of teaching the syntax of a programming language to novices, inspired by educational methods by which punctuation is taught to children. Hedy starts as a simple programming language without any syntactic elements such as brackets, colons or indentation. The rules slowly and gradually change until the novices are programming in Python. Hedy is evaluated on 9714 programs.