Buoyant plumes from solute gradients generated by non-motile Escherichia coli.

The effect of hydrodynamic mixing in bacterial populations due to bacterial chemotaxis is a well-described phenomenon known as bioconvection. Here we report the observation of buoyant plumes that result in hydrodynamic mixing, but in contrast to bioconvection the plumes form in the absence of bacterial motility. We propose that the buoyant flow originates from solute gradients created by bacterial metabolism, similar to solute-induced buoyant flow around growing protein crystals. In our experiments, metabolically-active non-motile Escherichia coli were layered along the bottom of flat-bottomed containers. The E. coli consumed glucose in the medium creating a lighter fluid beneath a heavier fluid. The situation is an example of Rayleigh-Taylor instability, in which a lighter fluid pushes on a heavier one. We developed a numerical model to study the effect of E. coli nutrient consumption and by-product excretion on extracellular solute gradients. The model solutions showed reduced-density fluid along the bottom of the fluid domain leading to buoyant plumes, which were qualitatively similar to the experimental plumes. We also used scaling analyses to study the dependence of plume formation on container size and cell size, and to investigate the effect of reduced gravity, such as the microgravity conditions encountered during spaceflight.

Shaking alone, without concurrent aeration, affects the growth characteristics of Escherichia coli.

AIMS: This study investigated the effects of linear vibration on cultures grown in both hard- and soft-sided containers to determine whether vibration alone affected the growth rate. METHODS AND RESULTS: Cultures of Escherichia coli were exposed to vibrational acceleration with and without access to additional oxygen. Vibrated cultures grown in hard-sided containers exited lag phase earlier and had a higher final yield than identical unshaken cultures, whether or not the cultures had access to ambient air. Cultures grown in soft-sided containers showed no response to vibration. CONCLUSIONS: Vibration in hard-sided containers decreases the length of the lag phase and increases final OD in E. coli, with or without increased oxygenation. Increased mixing and improved suspension, which result from vibration of cultures in hard-sided containers, are the most likely physical mechanisms for the more favorable culture conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper demonstrates that growth enhancement of shaken cultures is a function of the rigidity of the vessel even without aeration of the medium.

Developing capacity to protect human research subjects in a post-conflict, resource-constrained setting: procedures and prospects.

The capacity-building strategy used by a US-based research organisation, the Pacific Institute for Research and Evaluation (PIRE), to strengthen the system for the protection of human research subjects and the infrastructure of its international collaborating partner, the University of Liberia, are discussed. To conduct the much-needed biomedical and social science-based research-related activities in the future, this partnership is expected by PIRE to gradually evolve over time to strengthen the capacity of the local investigators and administrators of the University of Liberia. Accordingly, a unique opportunity to share technology and resources with a post-conflict, resource-constrained country is created by this partnership. This capacity-building model to strengthen the protection of human subjects in research can also be replicated in similar resource-constrained international settings and, accordingly, our experiences and limitations are shared in this paper.

Deception, power, and self-differentiation in college students' romantic relationships: an exploratory study.

The relationships among deception, power, and self-differentiation in college students' romantic relationships were explored. As hypothesized, lower total deception scores were found to significantly predict higher self-differentiation scores. Both men and women reported that men held significantly more power in their relationships. A secondary analysis revealed that men were significantly more likely than women to indicate they would be inclined to use deceptive strategies. Counter to the hypotheses, a significant negative correlation was not detected between power scores and omission scores, and positive relationships between power scores and contradiction scores were not found.

Abortion attitudes as determinants of perceptions regarding male involvement in abortion decisions.

Abortion decisions have a potentially meaningful effect on the lives of men. Previous research suggests that both men and women generally believe that men have the right to be involved in such decisions. However, very little research attention has been devoted to identifying individual difference correlates of discrepant levels of endorsement for male involvement in abortion decisions. The extent to which abortion attitudes (on a pro-choice to pro-life continuum), conceptualization of abortion as strictly a female issue, and interest in the issue operate as effective predictors of the appropriate level of male involvement in abortion decisions was examined in a sample of 1,387 college students. Results of a multiple regression analysis revealed that 44% of the variance in male involvement scores was explained by the predictor variables.

PIP: A survey was conducted among 1387 psychology students (429 men and 908 women) to explore correlates of perceptions of male involvement in abortion decisions by focusing on abortion attitudes on a pro-choice to pro-life continuum and on interest in the issue. Data collected through an Abortion Attitudes Survey, Interest in Abortion Survey, Abortion as a Female Issue Assessment, and Male Involvement in Abortion Decisions Scale. Results showed that more than half of the respondents held pro-life attitudes. The data further suggested that 14.3% of the students possessed relatively radical pro-choice attitudes, whereas 17.4% of the students expressed relatively radical pro-life attitudes. Furthermore, college students in the sample rated abortion as the most acceptable alternative in cases of rape and physical or mental deformity of the fetus. Abortion attitudes and opinions regarding the extent to which abortion should be conceptualized as strictly female issue were found to operate as effective predictors of perceptions regarding the appropriate level of male involvement in abortion decisions. Furthermore, the tendency to view abortion as an entirely female issue was inversely related to the level of male involvement deemed appropriate in abortion decisions.

Attitudes toward the level of men's involvement in abortion decisions.

College students completed a questionnaire that assessed their attitudes toward the level of male responsibility in abortion decisions. Overall, both men and women thought that men should have some degree of involvement in the abortion decision. However, as expected by the first hypothesis, men indicated a desire for more responsibility in the abortion decision than women thought the men should have. A second hypothesis predicted women would feel more strongly than men that abortion was strictly a woman's issue. Contrary to the hypothesis, women tended to disagree that abortion was strictly a women's issue. Implications of the findings are discussed.

Changes in attitudes toward homosexuality in college students: implementation of a gay men and lesbian peer panel.

The purpose of this study was to evaluate the implementation of a gay men and lesbian peer panel as an educational strategy in changing homophobic attitudes among 190 college students. The students were administered a modified version of the Attitudes Toward Homosexuality Scale before and after the intervention. Results indicated a significant difference between pre- and posttest scores. Men had more negative attitudes toward homosexuals than did women both before and after intervention. Suggestions for counselors, student development professionals, and other human service professionals pertaining to the delivery and format of the intervention are discussed.

Dating relationships and infidelity: attitudes and behaviors.

This study of 197 college student participants found that marital infidelity is significantly more unacceptable than dating infidelity. Men tended to be more lenient in their ratings of infidelity than women. Self-esteem scores were significantly higher for individuals who did not become involved in dating infidelity than for participants who did. However, self-esteem was not found to be a significant factor in whether a person remained in a current relationship in which the partner had been unfaithful.

Addiction versus intimacy as related to sexual involvement in a relationship.

Forty couples aged 18-25 years who were in love relationships of three months or more were tested concerning the level of addiction or maturity in the relationship. The results of three questionnaires revealed significant positive correlations between the following: self-esteem and maturity, adjustment and maturity, adjustment and relationship satisfaction, relationship satisfaction and maturity, relationship satisfaction and self-esteem, sexual satisfaction and maturity, and sexual satisfaction and relationship satisfaction. In a multiple regression, three variables (adjustment, relationship satisfaction, and intercourse) predicted a significant amount of the variance surrounding the maturity variable. The results supported the hypotheses proposed.

Coexistence of Prader-Willi syndrome, congenital ectropion uveae with glaucoma, and factor XI deficiency.

A patient with Prader-Willi syndrome and unilateral congenital ectropion uveae with glaucoma was found to have factor XI deficiency and reduced levels of serum luteinizing hormone, follicle-stimulating hormone, and testosterone. Administration of gonadorelin (LH-RH) increased serum levels of luteinizing hormone and follicle-stimulating hormone, while clomiphene citrate had no effect, suggesting a primary hypothalamic defect. Patients with congenital ectropion uveae should be followed up for the development of both glaucoma and neural crest disorders.