Statistical mechanics of geomagnetic orientation in sediment bacteria

Also published as: Biological Bulletin 159 (1980): 459-460Last year we reported on time-of-transit experiments in which magnetically orienting bacteria crossed a 1-mm stretch in the direction of a uniform magnetic field. The bacteria were found to behave as tiny self-propelled compass needles subject both to magnetic field alignment and to the randomizing effect of thermal agitation. In strong fields, magnetic bacteria are held in tight aligment; in weaker fields, their swimming paths meander more and transit times are greater. Paul Langevin derived an expression for the distribution of orientation in an ensemble of free-moving dipole particles as a function of ambient field strength. His theory becomes applicable to our experiments when bacterial migration is analyzed as a sequence of short steps during each of which the cell swims in a direction randomly selected from the Langevin distribution . The duration of each step, Δt, is actually a time constant of the cell's loss of directionality due to thermal agitation. By thus treating the migration as a process of random walk with drift, we are able to predict the mean and variance of the time of transit across a 1-mm stretch.Prepared for the Office of Naval Research under Contract N00014-79-C-0071

Balance in Family Triads:How Intergenerational Relationships Affect the Adult Sibling Relationship

In order to understand the interdependency between intergenerational and adult sibling relationships, a family systems perspective is applied to identify a smaller?empirically analyzable?relational unit of analysis, that is, the sibling?parent?sibling triad. Using balance theory, triadic configurations are derived that represent enhancement, compensation, and loyalty conflicts. The hypotheses are tested for three relational dimensions: support exchange, contact, and conflict. Multilevel analyses of 549 sibling?parent?sibling triads from the Netherlands Kinship Panel data show strong evidence for enhancement, whereas some indication was obtained for sibling relationships being affected by loyalty conflicts. The results underscore and substantiate interdependency between intergenerational and adult sibling relationships

No alignment of cattle along geomagnetic field lines found

This paper presents a study of the body orientation of domestic cattle on free pastures in several European states, based on Google satellite photographs. In sum, 232 herds with 3412 individuals were evaluated. Two independent groups participated in our study and came to the same conclusion that, in contradiction to the recent findings of other researchers, no alignment of the animals and of their herds along geomagnetic field lines could be found. Several possible reasons for this discrepancy should be taken into account: poor quality of Google satellite photographs, difficulties in determining the body axis, selection of herds or animals within herds, lack of blinding in the evaluation, possible subconscious bias, and, most importantly, high sensitivity of the calculated main directions of the Rayleigh vectors to some kind of bias or to some overlooked or ignored confounder. This factor could easily have led to an unsubstantiated positive conclusion about the existence of magnetoreception.Comment: Added electronic supplement with source dat

Smoking and alcohol consumption in relation to cognitive performance at middle age.

In the elderly, cigarette smoking has been related to reduced cognitive performance and moderate alcohol consumption to increased cognitive performance. It is not clear whether these associations also exist in middle age. The authors examined these relations in a population-based cohort study of 1,927 randomly selected, predominantly middle-aged subjects aged 45-70 years at the time of cognitive testing and living in the Netherlands. From 1995 until 2000, an extensive cognitive battery was administered, and compound scores were calculated. Risk factors had been assessed approximately 5 years previously. Multiple linear regression analyses (in which one unit of the cognitive score = one standard deviation) showed that, after the authors adjusted for age, sex, education, alcohol consumption, and cardiovascular risk factors, current smokers had reduced psychomotor speed (beta = -0.159, 95% confidence interval: -0.071, -0.244; p = 0.0003) and reduced cognitive flexibility (beta = -0.133, 95% confidence interval: -0.035,-0.230; p = 0.008) compared with never smokers. This effect was similar to that of being approximately 4 years older. Alcohol consumption was related to increased speed and better flexibility, especially among women who drank 1-4 alcoholic beverages a day. In conclusion, among middle-aged subjects, current smoking was inversely and alcohol consumption positively related to psychomotor speed and cognitive flexibility. This finding suggests that actions to prevent cognitive decline can be taken in middle age

Field experiments on electrically evoked feeding responses in the dogfish shark, Mustelus canis

Also published as: Biological Bulletin 159 (1980): 482From previous experiments, we learned that sharks, skates and rays have an electric sense that enables them to detect voltage gradients as low as 0.01 µV/cm within the frequency range from DC up to 8 Hz. The animals use their electric sense in predation, cuing in on the bioelectric fields commonly produced by fish and aquatic invertebrates. To quantify the response, we analyzed the feeding behavior of the shark Mustelus canis in Vineyard Sound off Cape Cod, Mass. An electrode panel was embedded in the ocean substrate in a water depth of 2-3m. Two salt-bridge electrodes, simulating a small prey fish, were placed 2 em apart at a distance of 15 cm from a centrally located odor source. Another pair of salt-bridge electrodes, simulating a larger fish, were placed 5 em apart at a distance of 30 cm on the other side of the odor source. DC current of 8 µA was applied to either one or both pairs of electrodes. Observations were made at night from a Boston Whaler with a glass bottomed observation well. Liquefied herring chum attracted and motivated sharks. In sum, the results support the conclusion that these sharks, once motivated by odor rely heavily upon their keen electric sense in executing their final strikes.Prepared for the Office of Naval Research under Contract N00014-79-C-0071

Stability of boundaries between response options of response scales: Does 'very happy' remain equally happy over the years?

__Abstract__ The differences between response scales in number and wording of response options make it hard to compare data from survey research and to perform research syntheses. A recent method that we have developed to tackle this problem is rooted in the idea that the transition points on a bounded continuum, on which verbal response options from a primary scale transit from one point to another, for instance from ‘happy’ to ‘very happy’, remain unchanged over time. The idea behind this is that although people may change their perception of, for example, their own happiness intensity over time, they are assumed not to change the degree of appreciation they attribute to the terms used to label response options. This is an important assumption for research syntheses that requires that everything remains unchanged, except for the change of interest. It means that if our method is applied to measurements at distinct points in time, differences in estimates of the mean and standard deviation can be attributed solely to changes in the frequency distributions on the primary scale. In this paper we apply the method to happiness and show that it is reasonable to assume that the transition points between the response options are stable over time

Nonresponse of secondary respondents in multi-actor surveys: Determinants, consequences, and possible remedies

Multi-actor survey data are highly valuable for answering questions about family relations, but the collection of such data is complicated by nonresponse among secondary (nonresident) respondents. Little is known, however, about the degree to which nonresponse of secondary respondents is selective and about the degree to which selective nonresponse biases substantive findings. Using a large representative survey, we analyze nonresponse of nonresident adult children of primary respondents. Nonresponse appears strongly related to characteristics of the parent–child relationship and to characteristics of both parents and children. Consequences are examined for three dependent variables: children’s attitudes, children’s support giving to parents and children’s well-being. Heckman models, which correct for sample selection bias, show that selective response hardly biases the substantive estimates. keywords: values; intergenerational relations; well-being; non-response; survey methodolog