Flavor-flavor associations induce hedonic shifts in taste preference

Two experiments allowed rats to drink freely two neutral flavors (almond and vanilla) in simultaneous compound with two hedonically valued flavors (quinine and saccharin). The neutral flavor previously paired with saccharin was subsequently preferred. The neutral flavor that had been paired with quinine was subsequently avoided. Experiment 3 found similar results when the animals were hand-fed a preset amount of the solution. Preference shifts were not obtained when differential amounts of the neutral flavors were consumed in isolation. The data indicate that flavor-flavor associations can shift taste preferences.     

Lernen an zwei Orten: das Problem des ‘Dualen System’ in der lehrerausbildung

On the basis of a study of the literature and of empirical research, the article puts forward suggestions for the improvement of teacher training programmes within a dual system.

A consecutive approach to training implies that a student spends a part of the training period in an educational institution and a part in a practical situation (i.e. on teaching practice). However, the consecutive system presents considerable problems in respect both of organisation and of the psychology of learning. Organisationally, there is the question of sequence to be faced, if the elements of theory and practice are to be brought together.

On the basis of a study of the literature of other forms of professional training, the following suggestions are made:

1. students’ activities in the school must re‐inforce their learning and be integrated with their work in the training institution;

2. their educational studies must support the acquisition of the competences needed by the teacher at the outset of his/her professional career;

3. attention must be paid to the learning needs and the potential of each student.

The article describes how a teacher training programme may follow these guidelines, leading to a ‘concurrent’ set of cycles bringing together elements of theory, practice and reflection upon practice, and in which a student may alternate between the academic institution and school practice.

After giving an overview of possible models of training the author focuses upon a specific example and provides a model of the institution‐practice link. What is important is that the learning style of the student be taken into account. Each student selects from four alternative programmes, namely: instructional variants, reflection variants, selfstudy variants, and practice variants. The contents of these four programmes are explained, and the learning outcomes of students from these differentiated programmes compared with those of students from undifferentiated, ‘normal’ programs. In summary, it is claimed that in the research project described there are positive indications for a theory‐practice link which gives students a choice of approaches and a better integration of their learning into the practical classroom situation.     

Preliminary studies on the detection ofMycobacterium avium-intracellulare complex using DNA probe from a clinical isolate

Genomic DNA from a clinical isolate ofMycobacterium avium-intracellulare complex was purified and cloned in PBR 322 at the tetracycline resistance site using Bam HI restriction enzyme. A 16 kb cloned fragment was purified, radiolabeled and used as a probe. Genomic DNA isolated from nineteen MAC strains, threeM. tuberculosis strains and oneM. kansasii strain were digested with Eco RI restriction enzyme, Southern blotted and hybridized with the 16 kb cloned and labeled fragment. Twelve MAC strains showed positive hybridization although five strains gave faint signals. Positive hybridization was noted in two out of the threeM. tuberculosis strains, possibly due to shared DNA homology. No signal was received from the singleM. kansasii strain used in this study.     

A theory for decoupling lossless coupled tapered lines with applications to directional couplers

A simple theory is presented for decoupling a pair of lossless coupled nonuniform transmission lines (CNUTL), with a common return and supporting TEM waves, into two lossless nonuniform transmission lines (NUTL). This theory is independent of the port terminations, symmetry conditions, etc. The method directly relates the line parameters of the lossless CNUTL's to those of the decoupled lines and vice versa; further, the matrix parameters of the CNUTL's as a four-port are explicitly expressed in terms of those of the decoupled lines as two-ports. This theory is then utilized to study the applications of CNUTL's as directional couplers.It is shown that for CNUTL's to behave as a codirectional coupler, each of the decoupled lines should be a proportional line, while for contradirectional coupler action, the two decoupled lines have to be duals of each other. The coupling response of the codirectional coupler is found to be periodic, while the phase shift between coupled and transmitted signals varies linearly with frequency. The coupling response of various contradirectional couplers with smooth transition at one of the ends, for which the decoupled lines are “basic NUTL's with hyperbolic solutions”, are studied in detail. It is shown that all these couplers have a high-pass response and that the CNUTL's with “hyperbolic cosine squared lines” as decoupled lines have the best response of all the CNUTL's considered.     

On orthogonal polynomials

A study is made of the orthogonal polynomials on certain curves in the complex plane. Necessary and sufficient conditions for a set of polynomials to be orthogonal on the curves are obtained in terms of symmetric matrices. The relations of the symmetric matrices to Toeplitz matrices and innerwise matrices are shown.     

A modal interpretation of wave propagation in non-homogeneous multiconductor systems

A generalized interpretation of the phenomenon of wave propagation in non-homogeneous multiconductor systems is given by introducing the concent of component waves. It is shown that the familiar analysis of homogeneous systems is only a particular case of the generalized approach developed in this paper.