Showing papers by "Harvard University published in 1976"

Decisions with Multiple Objectives: Preferences and Value Trade-Offs

Abstract: Many of the complex problems faced by decision makers involve multiple conflicting objectives. This book describes how a confused decision maker, who wishes to make a reasonable and responsible choice among alternatives, can systematically probe his true feelings in order to make those critically important, vexing trade-offs between incommensurable objectives. The theory is illustrated by many real concrete examples taken from a host of disciplinary settings. The standard approach in decision theory or decision analysis specifies a simplified single objective like monetary return to maximise. By generalising from the single objective case to the multiple objective case, this book considerably widens the range of applicability of decision analysis.

Symmetry Breaking Through Bell-Jackiw Anomalies

Abstract: In models of fermions coupled to gauge fields certain current-conservation laws are violated by Bell-Jackiw anomalies. In perturbation theory the total charge corresponding to such currents seems to be still conserved, but here it is shown that nonperturbative effects can give rise to interactions that violate the charge conservation. One consequence is baryon and lepton number nonconservation in $V\ensuremath{-}A$ gauge theories with charm. Another is the nonvanishing mass squared of the $\ensuremath{\eta}$.

Computation of the quantum effects due to a four-dimensional pseudoparticle

Abstract: A detailed quantitative calculation is carried out of the tunneling process described by the Belavin-Polyakov-Schwarz-Tyupkin field configuration. A certain chiral symmetry is violated as a consequence of the Adler-Bell-Jackiw anomaly. The collective motions of the pseudoparticle and all contributions from single loops of scalar, spinor, and vector fields are taken into account. The result is an effective interaction Lagrangian for the spinors.

Social Structure from Multiple Networks. I. Blockmodels of Roles and Positions

Abstract: Networks of several distinct types of social tie are aggregated by a dual model that partitions a population while simultaneously identifying patterns of relations. Concepts and algorithms are demonstrated in five case studies involving up to 100 persons and up to eight types of tie, over as many as 15 time periods. In each case the model identifies a concrete social structure. Role and position concepts are then identified and interpreted in terms of these new models of concrete social structure. Part II, to be published in the May issue of this Journal (Boorman and White 1976), will show how the operational meaning of role structures in small populations can be generated from the sociometric blockmodels of Part I.

Estimability and estimation in case-referent studies

Abstract: The concepts that case-referent studies provide for the estimation of "relative risk" only if the illness is "rare", and that the rates and risks themselves are inestimable, are overly superficial and restrictve. The ratio of incidence densities (forces of morbidity)-and thereby the instantaneous risk-ratio-is estimable without any rarity-assumption. Long-term risk-ratio can be computed through the coupling of case-referent data on exposure rates for various age-categories with estimates, possibly from the study itself, or the corresponding age-specific incidence-densities for the exposed and nonexposed combined-but again, no rarity-assumption is involved. Such data also provide for the assessment of exposure-specific absolute incidence-rates and risks. Point estimation of the various parameters can be based on simple relationships among them, and in interval estimation it is sufficient simply to couple the point estimate with the value of the chi square statistic used in significance testing.

Natural selection and random genetic drift in phenotypic evolution.

Abstract: In discussions of the major features of evolution, Simpson (1953) applied population genetic models to the interpretation of the fossil record Most population genetics theory concentrates on details of the genetic system, such as gene frequencies and recombination rates, which cannot be directly observed or inferred from measurements on polygenic characters Analysis of phenotypic data, particularly fossil material, requires models which are framed as much as possible in phenotypic terms Starting from a simple formula of quantitative genetics, the methods of population genetics are used here to make a theory of the evolution of the average phenotype in a population by natural selection and random genetic drift By analogy with Wright's (1931) adaptive topography for genotypes, Simpson (1953) proposed the concept of adaptive zones for phenotypes This is an intuitive method of visualizing the dynamics of phenotypic evolution in terms of the degree of adaptation of the various phenotypes in a population, it usually being thought that natural selection increases adaptation Such qualitative ideas are used by most evolutionary biologists and the notion of adaptive zones is popular among paleontologists In the present paper, the concept of adaptive zones is clarified by the construction of an adaptive topography for the average phenotype in a population This shows that with constant fitnesses the average phenotype evolves toward the nearest adaptive zone in the phenotype space But if fitnesses are frequency-dependent the average phenotype may evolve away from an adaptive zone A method is developed for estimating the minimum selective mortality necessary to produce an observed rate of evolution In examples of the evolution of tooth characters in Tertiary mammals, these minimum selective mortalities are found to be exceedingly small In his paper on the measurement of rates of evolution, Haldane (1949) stated that "The slowness of the rate of change makes it clear that agencies other than natural selection cannot be neglected because they are extremely slow by laboratory standards or even undetectable during a human lifetime" He briefly discussed mutation pressure Random genetic drift due to finite population size is another such agency The relative importance of natural selection and random genetic drift has been debated since Wright (1931, 1932) proposed that evolution is a stochastic process Fisher (1958), for example, believed that random genetic drift is insignificant in relation to natural selection The debate continues today at a more biochemical level (Lewontin, 1974) In order to objectively evaluate the role of random genetic drift in macro-evolutionary events, it is necessary to use mathematical models to determine the rate of evolution which can occur by repeated samplings of genetic material in a finite population This paper presents a statistical test for the hypothesis of evolution by random genetic drift, contingent on the effective population size In examples from the fossil record, it is found that rates of evolution equal to or greater than those observed have a significant probability of occurring by random genetic drift

Commodity Bundling and the Burden of Monopoly

Abstract: Presents information on a study which analyzed the prevalence of commodity bundling as a marketing strategy. Cost savings in production, transactions and information associated with commodity bundling; Characteristics of commodity bundling; Problems associated with convention price discrimination that can overcome by commodity bundling; Conclusions. (Из Ebsco)

Bounds and Self-Consistent Estimates for Creep of Polycrystalline Materials

Abstract: A study of steady creep of face centred cubic (f.c.c.) and ionic polycrystals as it relates to single crystal creep behaviour is made by using an upper bound technique and a self-consistent method. Creep on a crystallographic slip system is assumed to occur in proportion to the resolved shear stress to a power. For the identical systems of an f.c.c. crystal the slip-rate on any system is taken as $\gamma =\alpha (\tau /\tau \_{0})^{n}$ where $\alpha $ is a reference strain-rate $\tau $ is the resolved shear stress and $\tau \_{0}$ is the reference shear stress. The tensile behaviour of a polycrystal of randomly orientated single crystals can be expressed as $\overline{\epsilon}=\alpha (\overline{\sigma}/\overline{\sigma}\_{0})^{n}$ where $\overline{\epsilon}$ and $\overline{\sigma}$ are the overall uniaxial strain-rate and stress and $\overline{\sigma}\_{0}$ is the uniaxial reference stress. The central result for an f.c.c. polycrystal in tension can be expressed as $\overline{\sigma}\_{0}=h(n)\tau \_{0}$. Calculated bounds to $h(n)$ coincide at one extreme $(n=\infty)$ with the Taylor result for rigid/perfectly plastic behaviour and at the other $(n=1)$ with the Voigt bound for linear viscoelastic behaviour. The self-consistent results, which are shown to be highly accurate for $n=1$, agree closely with the upper bound for $n\geq 3$. Two types of glide systems are considered for ionic crystals: A-systems, {110} $\langle 110\rangle $, with $\gamma =\alpha (\tau /\tau \_{\text{A}})^{n}$; and B-systems, {100} $\langle 110\rangle $, with $\gamma =\alpha (\tau /\tau \_{\text{B}})^{n}$. The upper bound to the tensile reference stress $\overline{\sigma}\_{0}$ is shown to have the simple form $\overline{\sigma}\_{0}\leq A(n)\tau \_{\text{A}}+B(n)\tau \_{\text{B}};A(n)$ and $B(n)$ are computed for the entire range of $n$, including the limit $n=\infty $. Self-consistent predictions are again in good agreement with the bounds for high $n$. Upper bounds in pure shear are also calculated for both f.c.c. and ionic polycrystals. These results, together with those for tension, provide a basis for assessing the most commonly used stress creep potentials. The simplest potential based on the single effective stress invariant is found to give a reasonably accurate characterization of multiaxial stress dependence.

Haploidploidy and the evolution of the social insect

Abstract: Halminton (1) was apparently the first to appreciate that the synthesis of Mendelian genetics with Darwin's theory of natural selection had profound implications for social theory. In particular, insofar as almost all social behavior is either selfish or altruistic (or has such effects), genetical reasoning suggests that an individual's social behavior should be adjusted to his or her degree of relatedness, r, to all individuals affected by the behavior. We call this theory kinship theory. The social insects provide a critical test of Hamilton's kinship theory. When such theory is combined with the sex ratio theory of Fisher (9), a body of consistent predictions emerges regarding the haplodiploid Hymenoptera. The evolution of female workers helping their mother reproduce is more likely in the Hymenoptera than in diploid groups, provided that such workers lay some of the male-producing eggs or bias the ratio of investment toward reproductive females. Once eusocial colonies appear, certain biases by sex in these colonies are expected to evolve. In general, but especially in eusocial ants, the ratio of investment should be biased in favor of females, and in it is expected to equilibrate at 1 : 3 (male to female). We present evidence from 20 species that the ratio of investment in monogynous ants is, indeed, about 1 : 3, and we subject this discovery to a series of tests. As expected, the slave-making ants produce a ratio of investment of 1 : 1, polygynoys ants produce many more males than expected on the basis of relative dry weight alone, solitary bees and wasps produce a ratio of investment near 1 : 1 (and no greater than 1 : 2), and the social bumblebees produce ratios of investment between 1 : 1 and 1 : 3. In addition, sex ratios in monogynous ants and in trapnested wasps are, as predicted by Fisher, inversely related to the relative cost in these species of producing a male instead of a female. Taken together, these data provide quantitative evidence in support of kinship theory, sex ratio theory, the assumption that the offspring is capable of acting counter to its parents' best interests, and the supposition that haplodiploidy has played a unique role in the evolution of the social insects. Finally, we outline a theory for the evolution of worker-queen conflict, a theory which explains the queen's advantage in competition over male-producing workers and the workers' advantage regarding the ratio of investment. The theory uses the asymmetries of haplodiploidy to explain how the evolved outcome of parent-offspring conflict in the social Hymenoptera is expected to be a function of certain social and life history parameters.

Single-loop and double-loop models in research on decision making.

Abstract: September 1 976, volu me 21 Some current research and theory on organizational decision making from the political science literature is examined, in which the potential role of learning and feedback in the decision-making process is largely ignored. An espoused theory of action based on single-loop learning is found to be the most general model of action. A double-loop model is proposed as providing feedback and more effective decision making.

Polymers for the sustained release of proteins and other macromolecules

Abstract: SINCE the first demonstration that silicone rubber1 could be used as an implantable carrier for sustained delivery of low molecular weight compounds in animal tissues, various drug delivery systems have been developed. But except for the reports of Davis2,3 and Girnbrone et al.4, there has been little success in the development of slow release agents for large molecular weight compounds. Furthermore, the polymers used in those studies, polyvinylpyrrolidone and polyacrylamide, are often inflammatory in animal tissues and usually permit only brief periods of sustained release. We now present a simple method for incorporating various proteins and other macromolecules into non-inflammatory polymers. Sustained release of biochemically active macromolecules has been demonstrated for periods exceeding 100 d.

Implications of Dynamical Symmetry Breaking

Abstract: An analysis is presented of the physical implications of theories in which the masses of the intermediate vector bosons arise from a dynamical symmetry breaking. In the absence of elementary spin-zero fields or bare fermion masses, such theories are necessarily invariant to zeroth order in the weak and electromagnetic gauge interactions under a global $\mathrm{U}(N)\ensuremath{\bigotimes}\mathrm{U}(N)$ symmetry, where $N$ is the number of fermion types, not counting color. This symmetry is broken both intrinsically by the weak and electromagnetic interactions and spontaneously by dynamical effects of the strong interactions. An effective Lagrangian is constructed which allows the calculation of leading terms in matrix elements at low energy; this effective Lagrangian is used to analyze the relative direction of the intrinsic and spontaneous symmetry breakdown and to construct a unitarity gauge. Spontaneously broken symmetries which belong to the gauge group of the weak and electromagnetic interactions correspond to fictitious Goldstone bosons which are removed by the Higgs mechanism. Spontaneously broken symmetries of the weak and electromagnetic interactions which are not members of the gauge group correspond to true Goldstone bosons of zero mass; their presence makes it difficult to construct realistic models of this sort. Spontaneously broken elements of $\mathrm{U}(N)\ensuremath{\bigotimes}\mathrm{U}(N)$ which are not symmetries of the weak and electromagnetic interactions correspond to pseudo-Goldstone bosons, with mass comparable to that of the intermediate vector bosons and weak couplings at ordinary energies. Quark masses in these theories are typically less than 300 GeV by factors of order $\ensuremath{\alpha}$. These theories require the existence of "extra-strong" gauge interactions which are not felt at energies below 300 GeV.

Improvement in linearity and regulation of stiffness that results from actions of stretch reflex.

Abstract: We studied stretch reflexes of soleus muscles of intercollicularly decerebrated cats using a new technique for estimating the component of a stretch reflex that results from the purely mechanical p...

The Coming of the Post-Industrial Society

Abstract: (1976). The Coming of the Post-Industrial Society. The Educational Forum: Vol. 40, No. 4, pp. 574-579.

Olfactory neuroblastoma—A clinical analysis of 17 cases

Abstract: Seventeen patients with olfactory neuroblastoma seen at the Massachusetts General Hospital and Massachusetts Eye and Ear Infirmary from 1941 to 1971 are presented. Data on age, sex, symptoms, physical, and roentgenographic findings, and therapeutic results are evaluated. A system of pretherapy staging is proposed in which for Group A, the tumor is limited to the nasal cavity; in group B, the tumor is localized to the nasal acvity and paranasal sinuses; and in group C, the tumor extends beyond the nasal cavity and paranasal sinuses. Olfactory neuroblastoma is a radioresponsive, and, to a limited extent, radiocurable tumor and varies in aggressiveness. Of 17 patients in this series, 13 or 76% were alive without disease following treatment by surgery, irradiation, and combination of these two methods. Uncontrolled primary lesions with or without metastases accounted for all therapeutic failures. A treatment policy for this disease is presented.

The Elastic Properties of Composite Materials

Abstract: The determination of the elastic properties of composite materials (multiphase aggregates, polycrystals, and porous or cracked solids) from the elastic properties of the components may be approached in several ways. The problem may be treated statistically, via scattering theory, through variational principles, or by the assumption of specific geometries for the material under consideration. Each of these methods is reviewed in turn. The widely used Voigt-Reuss-Hill average can be a poor approximation for both two-phase composites and polycrystals, and its replacement by the two Hashin-Shtrikman bounds is recommended. For pore-containing or crack-containing media, specific geometry models must be considered if useful results are to be obtained. If aggregate theory is used to estimate the moduli of individual components of a composite whose bulk properties are known, the shear moduli of the component phases must be matched (within a factor of 2 or 3) for the method to be useful. Results for nonlinear composites (which allow calculation of the pressure variation of aggregate moduli) have been obtained for only a few special cases.

Rod outer segment disk shedding in rat retina: relationship to cyclic lighting

Abstract: When albino rats are reared in cyclic light, a burst of rod outer segment disk shedding occurs in the retina soon after the onset of light. The number of large packets of outer segment disks (phagosomes) in the pigment epithelium at this time is 2.5 to 5 times greater than at any other time of day or night. The subsequent degradation of large phagosomes to smaller structures within pigment epithelial cells proceeds rapidly. The burst of disk shedding follows a circadian rhythm for at least 3 days, since it occurs in continuous darkness at the same time without the onset of light.

Spin spin correlation functions for the two-dimensional Ising model: Exact theory in the scaling region

Abstract: We compute exactly the spin-spin correlation functions 〈σ0,0σM,N〉 for the two-dimensional Ising model on a square lattice in zero magnetic field for T>Tc and T

Prenatal genesis of connections subserving ocular dominance in the rhesus monkey.

Abstract: In foetal monkey brain neuronal projections carrying input from the two eyes initially overlap; they segregate during the second half of gestation and become fully separated in subcortical visual centres and partially separated in the cortex three weeks before birth and thus before visual experience.

The blue reaction product in horseradish peroxidase neurohistochemistry: incubation parameters and visibility.

Abstract: A blue reaction product is formed at sites that contain horseradish peroxidase (HRP) activity when benzidene is used as the chromogen. With neutral red as a counter stain, this method affords excellent visualization of both retrograde and orthograde axonal transport of intracerebrally injected HRP. The visibility of this blue reaction-product is better than the visibility of the brown reaction-product obtained in the commonly used diaminobenzidene procedures. Variations in incubation times and reagent concentrations resulted in significant differences in the extent to which transported HRP could be demonstrated with benzidene. One of these benzidene procedures demonstrated a wider extent of HRP transport than a representative diaminobenzidene procedure. The substantia nigra and the nucleus locus ceruleus did not display artifactual deposition of the blue reaction-product.

Natural Concepts in Pigeons.

Abstract: Pigeons learned to discriminate pictures of trees, bodies of water, or a particular person in three separate experiments. Pictures being seen for the first time were discriminated almost as well as pictures seen in training. The pigeons in each experiment showed similar patterns of errors and correct discrimination.

Protein-folding dynamics.

Abstract: In a discussion of the dynamics of protein folding two limiting models (random-search nucleation and chain propagation., diffusion–collision) are considered. It is suggested that the latter may have the dominant role in many proteins.

The evolutionary strategy of the equidae and the origins of rumen and cecal digestion.

Abstract: There are two main groups of ungulates or hoofed mammals living today, perissodactyls and artiodactyls. They are distinguished by a basic difference in foot morphology, which indicates that the two groups arose independently from a basal "proto-ungulate" stock (the order Condylarthra) in the early Tertiary. This difference involves the axis of symmetry of the foot. In perissodactyls it passes through the third metapodial, while in artiodactyls it passes between the third and fourth metapodials. The perissodactyls surviving today are horses, rhinos and tapirs. The recent artiodactyls are a much larger and more diverse group, broadly covering all "cloven-hoofed" animals such as pigs, hippos, camels, deer, giraffes, antelope, cattle and sheep. The perissodactyls must have evolved by the late Paleocene, as by the early Eocene four out of five of the known superfamilies are already distinguishable (Romer, 1966). Artiodactyls are also seen in the early Eocene (Romer, 1966), but the two major groups of ruminant artiodactyls, the tylopods and the pecorans, do not appear in the fossil record until the late Eocene (Gazin, 1955) (see Fig. 1). The perissodactyls were the dominant medium to largesized herbivores during the Eocene, and in the early Oligocene a reduction in their diversity coincided with the beginning radiations of the ruminant groups of artiodactyls. These latter animals were the dominant medium-sized herbivores throughout the remainder of the Tertiary, at least in terms of species diversity. The perissodactyls originated in North America; the origin of the artiodactyls, whether in North America or in Eurasia, is still in question (Olson, 1971). As the rise of the artiodactyls at the Eocene-Oligocene boundary coincides with the decrease in the diversity of the perissodactyls, theories have been advanced to explain this coincidence in terms of perissodactyls being competitively inferior to artiodactyls. One obvious difference between the two groups is the difference in limb morphology. Although the axis of symmetry of the foot seems an unlikely candidate for conferring a selective advantage, artiodactyls do possess a unique double trochleared tarsal or ankle joint. This structure has been regarded as a key feature of the group and contributory to their evolutionary success, on the grounds that it has enabled artiodactyls to achieve rapid acceleration for predator escape (e.g., Schaeffer, 1947; Romer, 1968; Colbert, 1969). While there is little doubt that this particular adaptation was of value to the artiodactyls themselves, I do not think, however, that it had a great deal to do with the relative competitive efficiencies of these two ungulate groups. For a start, this tarsus appeared in a highly advanced condition in the first artiodactyls in the early Eocene (Schaeffer, 1947) long before their radiation and diversification, and is found in noncursorial as well as cursorial forms. In addition, modern ecological work demonstrates that predation is not necessarily detrimental

Inherited retinal dystrophy: primary defect in pigment epithelium determined with experimental rat chimeras

Abstract: Chimeric rats were produced by the aggregation of embryos of the pinkeyed, retinal dystrophic RCS strain with those of pigmented, normal rats. In the mosaic eyes, patches of neural retina with abnormal and degenerated photoreceptors were present only opposite patches of nonpigmented, mutant pigment epithelium. This indicates that the retinal dystrophy gene acts in the pigment epithelial cell rather than in the photoreceptor cell.

Breakups Before Marriage: The End of 103 Affairs

Abstract: Factors that predicted breakups before marriage, investigated as part of a two-year study of dating relationships among college students, included unequal involvement in the relationship (as suggested by exchange theory) and discrepant age, educational aspirations, intelligence, and physical attractiveness (as suggested by filtering models). The timing of breakups was highly related to the school calendar, pointing to the importance of external factors in structuring breakups. The desire to break up was seldom mutual; women were more likely than men to perceive problems in premarital relationships and somewhat more likely to be the ones to precipitate the breakups. Findings are discussed in terms of their relevance for the process of mate selection and their implications for marital breakup. (“The best divorce is the one you get before you get married.”)