Showing papers by "University of Massachusetts Boston published in 1977"

Observation of Amplification in a Strongly Driven Two-Level Atomic System at Optical Frequencies

Abstract: We report the observation of optical amplification in a two-level atomic system driven by a strong, resonant field. By exciting an atomic beam of two-level sodium atoms simultaneously with a strong, fixed-frequency driving field and a weak, tunable, probe field, we have measured the absorption (amplification) line-shape function for several values of driving field strength. In addition, we have verified theoretical predictions that higher amplification is obtained when the strong field is detuned from exact resonance.

Hybridization of maize and teosinte, in mexico and guatemala and the improvement of maize

Abstract: The recognition and subsequent detection of the importance of teosinte introgression in the racial diversity and heterotic gene architecture of maize has been one of the outstanding achievements of Paul C. Mangelsdorf’s investigations into the origin of maize. This paper documents three areas in Mexico and Guatemala where maize and teosinte hybridize and where there is a system by which native cultivators exploit the heterotic nature of maize to increase their harvest. There is little reason to doubt that the hybridization and subsequent introgression of teosinte genes into maize observed at these sites is changed from that which has occurred over the past three thousand years resulting in the tremendous diversity and pronounced hybrid vigor in maize.

The reproductive biology of cupania guatemalensis radlk. (sapindaceae).

Abstract: Intraspecific floral polymorphism is of widespread occurrence in flowering plants. Perfect, staminate, and pistillate flowers may be found on the same or different plants in diverse combinations as exemplified by monoecy, dioecy, androdioecy, gynodioecy, polygamy and the like; in addition, within perfect-flowered species, polymorphism may exist in the form of distyly and tristyly. It is generally presumed that floral polymorphisms increase the probability of outcrossing. The level of outcrossing, however, has not been measured in any zoophilous species with polymorphic flowers except for some heterostylous species (Ornduff, 1971, 1975). Floral polymorphism, by introducing spatial variation in floral rewards, also influences the foraging behavior of pollinators. The foraging behavior of pollinators, in turn, is likely to influence not only gene flow but also the evolution of floral polymorphism itself. Yet it is somewhat surprising that the effect of floral polymorphism on the foraging behavior of pollinators has not so far been examined. This paper describes the reproductive biology of a monoecious species, Cupania guatemalensis Radlk. (Sapindaceae), a small tree found in lowland tropical forests of Central America. It examines the pattern of spatial and temporal variation in the relative frequencies of staminate and pistillate flowers at the individual and population levels; differences in floral reward of staminate and pistillate flowers; differences in the foraging behavior and visitation rates of pollinators on staminate and pistillate flowers; and the effect of flowering behavior and floral polymorphism on the foraging behavior of pollinators and the degree of outcrossing. In addition, the floral phenology of some other members of the Sapindaceae is interpreted in the light of findings reported here. The investigations are part of a wider study of the breeding systems of lowland tropical forest trees (Bawa, 1974; Bawa and Opler, 1975).

Zonation in deep - sea gastropods: the importance of biological interactions to rates of zonation

Abstract: The multivariate techniques of cluster analysis and factor analysis were used to study depth-correlated changes in the species composition of deep-sea gastropod assemblages. The most pronounced faunal change occurred at the shelf-slope transition. The fauna changed continuously from the upper slope to the abyss and the rate of change seemed proportional to the rate of change in depth, being highest on the slope, lowest on the abyss and intermediate on the abyssal rise. This pattern may reflect an increasingly uniform environment with increasing depth. It is suggested that differing rates of zonation among components of the deep-sea benthos are determined, in part, by biological interactions. Groups dominated by croppers and predators such as the epibenthic macrofauna and gastropods are zoned more rapidly than infaunal deposit feeders. This may result because vertical ranges along the depth gradient are more compressed by interspecific competition in members of higher trophic levels. Predation may alleviate competition among infaunal groups at lower trophic levels permitting their ranges to overlap more extensively and consequently diminishing their rates of faunal change with depth. In support of this hypothesis, it is shown that rates of zonation in the epifauna, gastropods and the infaunal polychaetebivalve fraction correspond to their relative positions in the trophic structure.

Spatial relationships between staminate and pistillate plants of dioecious tropical forest trees.

Abstract: Alternate floral morphs in the form of dioecious, gynodioecious, distylous and tristylous plants within the same species are of widespread occurrence among flowering plants. The spatial distribution of different floral morphs, and therefore floral resources, within a population is likely to influence the foraging behavior of pollinators and concomitantly, the level of pollination. This distribution might also indicate the extent to which plants with different floral morphs exploit different microhabitats, particularly in dioecious species in which sexual dimorphism is most pronounced. Recently, Levin (1974) and Ornduff and Weller (1975) have analyzed the spatial distribution of pins and thrums among distylous Hedyotis nigricans (Rubiaceae) and Jepsonia heterandra (Saxifragaceae), respectively. However, to the best of our knowledge, no such analysis exists for a dioecious species despite the fact that dioecy is much more common than heterostyly, especially in species-rich tropical forests (see Ashton, 1969; Bawa, 1974; Bawa and Opler, 1975). Herein, we report the dispersion patterns of staminate and pistillate plants of several dioecious tree species that occur in tropical lowland forests of Costa Rica. The objective of the study was to investigate: a) if staminate and pistillate plants of the same species display spatial segregation, b) if the dispersion pattern indicates asexual reproduction by one or both sexes, and c) if the distribution of one sex might be more correlated with a particular environmental factor than the other. The study is part of a wider investigation dealing with ecological aspects of dioecism in tropical forests (Bawa and Opler, 1975, 1977; Opler and Bawa, 1977).

Elastic scattering, transfer reactions, and fission induced by O-16 ions on Ta-181 and Pb-208

Abstract: Total cross sections for the quasielastic and fission channels in reactions of $^{16}\mathrm{O}$ on $^{181}\mathrm{Ta}$ and $^{208}\mathrm{Pb}$ were measured as a function of the incident energy near the Coulomb barrier. For $^{208}\mathrm{Pb}$, the fission and quasielastic components account for essentially all of the total reaction cross sections as deduced from the elastic scattering. However, for $^{181}\mathrm{Ta}$, the fission and quasielastic components account for only about 25% of the total cross section as deduced from elastic scattering. The fission fragment angular distributions for $^{208}\mathrm{Pb}$ are analyzed with a simple statistical approach yielding an effective moment of inertia at the saddle point compatible with the liquid-drop-model prediction. Fission excitation functions for $^{181}\mathrm{Ta}$ are described reasonably well by a statistical evaporation code.NUCLEAR REACTIONS Ta($^{16}\mathrm{O}$, $^{16}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{17}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{15}\mathrm{N}$), ($^{16}\mathrm{O}$, C), ($^{16}\mathrm{O}$, $f$), ${E}_{L}=83, 90, 96$ MeV. $^{208}\mathrm{Pb}$($^{16}\mathrm{O}$, $^{16}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{17}\mathrm{O}$), ($^{16}\mathrm{O}$, $^{15}\mathrm{N}$), ($^{16}\mathrm{O}$, C) ${E}_{L}=80, 83, 88, 90, 96, 102$ MeV, measured $\ensuremath{\sigma}(\ensuremath{\theta}, E)$. $\mathrm{Ta}(^{16}\mathrm{O}, f)$ ${E}_{L}=77\ensuremath{-}102$ MeV, measured $\ensuremath{\sigma}(E)$; deduced optical-model parameters, total reaction cross sections; enriched targets.

Physical stigma and academic performance as factors affecting children's first impressions of handicapped peers.

Abstract: The effects of four variables on attitudes toward children were studied: the sex and social status of the rater and the physical appearance and academic competence of the target child being rated. The results indicated that competent and physically nonstigmatized children were rated more favorably than incompetent and physically stigmatized children. The data also revealed that girls had a significantly more positive stereotype than did boys of a competent male target child but that boys were more willing to be in physical proximity to the male target child as measured by a social-distance scale. Finally, the results indicated that popular children rated the attractive and competent target child less favorably than children who were not so popular. However, the popular children rated the attractive and incompetent target child more favorably than the less popular children did. The findings were discussed in terms of the salience of physical labels (i.e., stigma) on attitudes toward children.

Sex Discrimination after Death

Abstract: Death notices and obituaries published during the same calendar month (March, 1975) by daily newspapers in Boston and New York were examined for possible sex bias. A clear pattern of male preference was found. A disproportionately low number of women received obituaries, and female obituaries were also shorter. The likelihood of a recently deceased male receiving an obituary with a photograph was approximately ten times greater than that of a female. These results suggest that terminal rites of passage tend to confirm and perpetuate rather than challenge or transfigure previously existing values. Discussion includes possible use of obituaries as an unobtrusive measure of social change, as well as some aspects of the death system's involvement in discriminatory policies.

How to Brace a One-Story Building

Abstract: This paper describes the economical placing of braces in the walls and ceiling of a rectangular one-story building. First, efficient schemes for bracing the ceiling are shown to correspond to trees...

Memories of Tomorrow: On the Interpenetrations of Time in Later Life

Abstract: Why would you and I be here today unless each of us had some private fascination with time? And how would we have anything substantial to share with each other unless, over the years, some of this private fascination had been transformed into controlled observations and all the rigorous maneuvers of scientific theory and research? Yet I continue to wonder how well our studies represent the experiential world of psychological time. Consider, for example, the meanings and uses of time for those who have themselves survived the passing of many hours, years, and decades. It is doubtful that either popular stereotypes or the available research do justice to the varieties of time experience at their command.

The Conjunctival Sickling Sign, Hemoglobin S, and Irreversibly Sickled Erythrocytes

Abstract: • Sixty-five patients with hemoglobins AS, SC, and SS were investigated in a masked fashion. We observed a statistically significant positive correlation between the severity of conjunctival sickling signs and the counts of irreversibly sickled cells in each hemoglobinopathy group. We also observed a statistically significant positive correlation between the severity of the conjunctival vasculopathy and the percentage of sickle hemoglobin in the total group of patients with hemoglobins AS, SC, and SS. ( Arch Ophthalmol 95:808-811, 1977)

Part two: Diabetes, culture change, and acculturation: A biocultural analysis 1

Abstract: Acculturational trends related to diet and energy expenditure were examined in non‐Western societies noted for significantly increased incidence of maturity‐onset diabetes mellitus. Crosscultural analysis of these trends indicates that increased incidence levels were often preceded by acculturation, suggesting that diabetes mellitus may be a disordered physiological and psychological adaptation to rapid cultural change. Increased incidence preceded by lifestyle changes and total immersion in a new culture in non‐Western and Western societies is also included.

Optic Disc Neovascularization of Uveal (Choroidal or Posterior Ciliary) Origin

Abstract: • Fluorescein angiography during the choroidal phase of perfusion has been used to study the origin of blood vessels comprising neovascular tissue of the disc. These newly formed vessels were shown to derive their blood supply primarily from the uveal circulation rather than from the retinal circulation. This is related to the observation that many normal disc blood vessels originate from the choroidal or posterior ciliary circulation. ( Arch Ophthalmol 95:998-1003, 1977)

We Covered Death Today.

Abstract: Death education is passing over the invisible threshold to social acceptance. This “success,” however, brings a new set of risks. Focus in this article is upon the possibility that death education might be manipulated to serve as a more sophisticated form of denial rather than an open and disciplined inquiry into our relationship with mortality. Trends toward narrowing and neutralizing the subject can already be seen. The full scope of death-related issues is often reduced to selected aspects of the dying process. This makes it easier to retain the illusion of control which, in turn, reduces anxiety. The neutralizing process can be seen in the assimilation of death as just one more fact of life. We accept those connotations of death that support the personal and social status quo, but continue to ignore or deny death's most unique implications. It is recommended that the death educator be aware of the social pressures and expectations to deliver a comforting “product” rather than a searching enco...

Psychological differentiation, event uncertainty, and heart rate.

Abstract: Psychological differentiation and uncertainty about receiving a painful noise were examined for their effects on heart rate during the anticipatory, impact and recovery phases of the tone presentation. Psychologically differentiated and nondifferen-tiated subjects were randomly assigned to three event uncertainty conditions (5 percent, 50 percent, 95 percent probability of noise). Subjects were informed of the probability of receiving the noise, as well as the time of occurrence as indicated by a sequentially numbered visual display. Subjects received the noise on the second of the experiment s two trials. Cognitive style and event uncertainty interacted during the anticipatory phase — i.e., differentiated subjects showed a monotonic increase in heart rate with increasing probability of receiving the noise that represents preparation for instrumental activity. Results are consistent with the theory that meaningful personality-stress relationships may be obtained when examining stimulus-oriented d...

Bracing Grids of Cubes

Abstract: The paper describes the minimally redundant sets of diagonal braces in a grid of cubes in space. The language developed is essentially graphical. The methods extend those of the first few sections of an earlier work by Bolker and Crapo (1977).

Gene Differences between the Sex Ratio and Standard Gene Arrangements of the X Chromosome in DROSOPHILA PERSIMILIS

Abstract: The sibling species Drosophila pseudoobscura and D. persimilis each carry two gene arrangements in the right arm of the X chromosome; Standard (ST) and Sex Ratio (SR). The SR sequence of D. persimilis and the ST sequence of D. pseudoobscura have the same banding pattern. These cytologically identical arrangements carry different alleles at the esterase-5 (Est-5) and phosphoglucomutase-1 ( Pgm-1) loci. All the alleles on the SR arrangement of D. persimilis are also present on the ST arrangement of that species, and the same allele was most common in all cases. However, the allele frequencies at the Pgm-1 locus are significantly different between the two arrangements. Within the ST arrangement of D. persimilis, the alleles at the Est-5 and Pgm-1 loci are in linkage equilibrium.

The effect of impurities on the spin-density-wave transition

Abstract: The effect of impurities on the second order phase transition into the commensurate spin-density-wave state is considered for a two-band itinerant-electron antiferromagnet with imperfect nesting. The enhancement of electron-hole pairing by polarized magnetic impurities and the pair destruction effect of scattering by both magnetic and non-magnetic scatters is exhibited in a calculation of the dependence of the Neel temperature on magnetic impurity concentration and on the degree of imperfect nesting. The commensurate SDW is shown to be stabilized by magnetic impurities.