The patterns of abundance generated by a simple stochastic birth-death-immigration model are described in order to characterize the diversity of neutral communities of ecologically equivalent species. Diversity is described by species number S and the variance of frequency or log abundance q∼. The frequency distribution of abundance is very generally lognormal, skewed to the left by immigration and resembling descriptions of natural communities. Increased immigration and community size always cause S to increase. Their effect on q∼ is more complicated, but given biologically reasonable assumptions, S and q∼ will be positively correlated in most circumstances. Larger samples contain more species; the graph of log S on log individuals, equivalent to a species-area curve, is generally convex upward but becomes linear with a slope of about +0.25 when immigration is low and births exceed deaths. When individuals invade a new, vacant environment, both S and q∼ increase through time. Thus, a positive correlation between S and q∼ will usually be generated when sites of differing size or age are surveyed. At equilibrium, communities maintain roughly constant levels of S and q∼ but change in composition through time; composition may remain similar, however, for many generations. Many prominent patterns observed in natural communities can therefore be generated by a strictly neutral model. This does not show that community structure is determined exclusively by demographic stochasticity, but rather demonstrates the necessity for an appropriate null model when functional hypotheses are being tested.

In the name of equity, we. .. seek dramatic improvement in the quality of the education available to our children. Any steps to achieve desegregation must be reviewed in light of the black community's interest in improved pupil performance as the primary characteristic of educational equity. TVe define educational equity as the absence of discriminatory pupil placement and improved performance for all children who have been the objects of discrimination. We think it neither necessary, nor proper to endure the dislocations of desegregation without reasonable assurances that our children will instructionally profit. Coalition of black community groups in Boston' * This paper is a part of a larger study on the Roles of Courts in Desegregation of Education Litigation sponsored by the Institute of Judicial Administration through a grant from the Ford Foundation. The results of this research will be published in a forthcoming book on this subject. t Professor of Law, Harvard University. Pamela Federman, Susan Mentser, and Margaret Stark Roberts assisted in researching and preparing this article. 1. Freedom House Institute on Schools and Education, Critique of the Boston School Committee Plan, 1975, at 2 (emphasis added) (on file with Yale Law Journal). This 15 page document was prepared, signed, and submitted in February, 1975, directly to federal judge IV. Arthur Garrity by almost two dozen of Boston's black community leaders. The statement was a critique of a desegregation plan filed by the Boston School Committee in the Boston school case:

Cognitive rehabilitation for mild cognitive impairment (MCI) and early Alzheimer's disease is readily available to the geriatric population. Initial evidence suggests that techniques incorporating motivational strategies to enhance treatment engagement may provide more benefit than computerised training alone. Seventy four adults with subclinical cognitive decline were randomly assigned to computerised cognitive training (CCT), Cognitive Vitality Training (CVT), or an Active Control Group (ACG), and underwent neuropsychological evaluations at baseline and four-month follow-up. Significant differences were found in changes in performance on the Modified Mini Mental State Examination (mMMSE) and measures of verbal learning and memory across treatment groups. Experimental groups showed greater preservation of functioning on the mMMSE than the ACG group, the CVT group performed better than the ACG group on one measure of verbal learning and both measures of verbal memory, and the CCT group performed better than the ACG group on one measure of verbal learning and one measure of verbal memory. There were no significant group differences between the CVT and CCT groups on measures of verbal learning or memory. It was concluded that computerised cognitive training may offer the most benefit when incorporated into a therapeutic milieu rather than administered alone, although both appear superior to more generic forms of cognitive stimulation.

Competitive interactions between coinfecting genotypes of the same pathogen can impose selection on virulence, but the direction of this selection depends on the mechanisms behind the interactions. Here, we investigate how host immune responses contribute to competition between clones in mixed infections of the rodent malaria parasite Plasmodium chabaudi. We studied single and mixed infections of a virulent and an avirulent clone and compared the extent of competition in immunodeficient and immunocompetent mice (nude mice and T cell-reconstituted nude mice, respectively). In immunocompetent mice, the avirulent clone suffered more from competition than did the virulent clone. The competitive suppression of the avirulent clone was alleviated in immunodeficient mice. Moreover, the relative density of the avirulent clone in mixed infections was higher in immunodeficient than in immunocompetent mice. We conclude that immune-mediated interactions contributed to competitive suppression of the avirulent clone, although other mechanisms, presumably competition for resources such as red blood cells, must also be important. Because only the avirulent clone suffered from immune-mediated competition, this mechanism should contribute to selection for increased virulence in mixed infections in this host-parasite system. As far as we are aware, this is the first direct experimental evidence of immune-mediated apparent competition in any host-parasite system.