The jamming avoidance response in the weakly electric fishEigenmannia

This study analyzes the algorithm by which the animal's nervous system evaluates spatially distributed temporal patterns of electroreceptive information. The outcome of this evaluation controls the jamming avoidance response, which is a shift in the animal's electric organ discharge frequency away from similar foreign frequencies. The encoding of “behaviorally relevant” stimulus variables by electroreceptors and the central computation of their messages are investigated by combined behavioral and neurophysiological strategies.     

Intragroup dynamics of a cooperative breeder: An anlysis of reproductive roles in the acorn woodpecker

Summary The acorn woodpecker is a cooperative breeder generally thought to breed promiscuously within groups, but alternative patterns of reproductive investment can be expected and remain to be examined. With this feature of mating system in mind, we studied the reproductive roles of individuals in a single group of this species in central coastal California over a three-year period. Particularly detailed observations were made in 1979, when the group consisted of two potentially breeding sibling males and a single breeding female. One male (298) contributed significantly more than 297 in virtually all aspects of nest and fledgling care. These include (1) feeding nestlings, (2) nest sanitation, (3) nocturnal incubation and brooding, (4) feeding fledglings, and (5) escorting fledglings. In the few observed and rarely occurring dominance interactions, 298 prevailed. These results suggest that 298 had a higher probability of fathering the group's two 1979 offspring than did his brother. Thus, the two males differed substantially in their parental roles within the group, and very likely in reproductive roles, also. At present stage of knowledge, monogamy in groups with one female and more than one potential reproductive male is no less likely than promiscuity. These findings are discussed with respect to the evolution of cooperative breeding in this species.     

Translation of user requirements into house designs: A multi-dimensional scaling analysis

An experiment was conducted to determine how user requirements for single-storey houses are translated into actual design layouts. Architectural students were asked to provide floorplans of houses for four quite different hypothetical users. The briefs contained information either about spatial requirements or about life-style characteristics. Another group of architectural students later evaluated the appropriateness of the designs for the intended user. An INDSCAL analysis of the data (inter-room distances) produced a 4-dimensional solution that accounted for 65% of the variance between house designs. The salience of the dimensions seemed to be more a function of the designer than of the requirements of the user.It was found that when users' requirements are expressed in spatial terms only, the designs produced are clearly a function of the user, not the designer. The more information supplied about the user, the greater the tendency for congruence in the designs. When the brief consisted of life-style characteristics only, the results remained equivocal. There appeared to be little consensus on what designs were appropriate for the hypothetical users.The experiment strongly suggested that (a) architecture students handle information about spatial requirements with ease and with a good deal of consensus on what they consider to be the appropriate design solution for each user; (b) information about life-style characteristics and activity profiles, on the other hand, is handled quite differently by different students. In the latter case, the house designs produced probably follow implicit design-behaviour theories that are quite idiosyncratic. A number of theoretical and methodological issues that require further investigation are raised in the discussion.     

Recent introduction of an Asian estuarine copepod,Pseudodiaptomus marinus (Copepoda: Calanoida), into southern California embayments

Past studies made between 1938 and the mid-1970's of coastal embayments between northern Baja California and Oregon (USA) established the presence of only one species of the calanoid copepod genus Pseudodiaptomus, P. euryhalinus. This species is endemic to warm temperate latitudes of western North America. We now report the presence of breeding populations of the Asian calanoid copepod P. marinus in two Southern California embayments, Mission Bay and Agua Hedionda Lagoon. The Mission Bay population was monitored monthly from December 1986 to June 1987 and showed evidence of continuous breeding and growth. The regional, endemic species, P. euryhalinus, was not observed in either embayment. Mechanisms that might account for the apparent recent introductions of P. marinus into Southern California include dispersion by ocean circulations and transport by transoceanic ships. In the present case, the explanation is that the introduction is most likely a direct consequence of aquaculture projects. Remaining to be confirmed by systematic sampling is the apparent disappearance of P. euryhalinus from embayments dominated by P. marinus.     

Characterization of hydrocarbon pollutant burdens in petrochemical and refinery process streams

This paper describes techniques which provide for both qualitative and quantitative identification of major components in a process stream. The techniques and instrumentation have been deliberately chosen so as to be within the technical and financial reach of all but the smallecompany laboratory. The sample preparation steps consist of an initial series of extractions which isolate compounds into organic acid, base, and neutral compounds and a totally water soluble phase. Each fraction is then concentrated and subjected to thin-layer chromatography, gas chromatography, infrared spectroscopy or ultraviolet spectroscopy as appropriate. Results are given for laboratory samples, one a mixture of aniline, phenol, benzoic acid, m-nitrobenzaldehyde, 1-butanol, 2-hexanone, nonane, and cyclohexane, and the other a mixture of benzene, ethylbenzene, and styrene. Also, a qualitative analysis of a petroleum refinery desalter water is presented.