Showing papers by "Yale University published in 1974"

Intermittent turbulence in self-similar cascades: divergence of high moments and dimension of the carrier

Abstract: Kolmogorov’s “third hypothesis” asserts that in intermittent turbulence the average \( \bar \varepsilon \) of the dissipation e, taken over any domain D, is ruled by the lognormal probability distribution. This hypothesis will be shown to be logically inconsistent, save under assumptions that are extreme and unlikely. A widely used justification of lognormality due to Yaglom and based on probabilistic argument involving a self-similar cascade, will also be discussed. In this model, lognormality indeed applies strictly when D is “an eddy,” typically a three-dimensional box embedded in a self-similar hierarchy, and may perhaps remain a reasonable approximation when D consists of a few such eddies. On the other hand, the experimental situation is better described by considering averages taken over essentially one-dimensional domains D.

Incentives and risk-sharing in sharecropping

Abstract: At least from the time of Ricardo, economists have begun their investigations of how competitive markets work, how wages, rents and prices are determined, by a detailed examination of agriculture. Even today, agriculture is taken as the paradigm-and perhaps almost the only important example-of a truly competitive market (or at least this was the case until the widespread government intervention in this market). For a number of years I have been concerned with how competitive markets handle risk taking, and how risk affects real resource allocation. Risks in agriculture are clearly tremendously important, yet remarkably the traditional theoretical literature has avoided explicit treatment 3 of risk sharing in agricultural environments. The consequences of this are important. First, it makes suspect the traditional conclusions regarding sharecropping. Is it really true that sharecropping results in too low a supply of labour, because workers equate their share of output times the (value of the) marginal productivity of labour to the marginal disutility of work, whereas Pareto optimality requires the (value of the) marginal productivity of labour be equal to the marginal disutility of work? Or is it true, as Wicksell asserted, that there is no distincion between landlords hiring labour or labour renting land? Second, it leaves unanswered many of the important economic questions. How is the equilibrium share determined? Why have some economies (in the past or at present) used one distribution system, other economies used others? Our object is to formulate a simple general equilibrium model of a competitive agricultural economy. (Other general equilibrium models of competitive economies with uncertainty have been formulated by Arrow [2] and Debreu [9], Diamond [10], and Stiglitz [14]. Each of these has its serious limitations in describing the workings of the modern capitalist economy. (See Stiglitz [15]).) The model is of interest not only for extending our understanding of these simple economies but also in gaining some insight into the far more complex phenomena of shareholding in modern corporations. Our focus is on the risk sharing and incentive properties of alternative distribution systems. The analysis is divided into two parts. In the first, the amount of labour (effort) supplied by an individual is given, and the analysis focuses on the risk sharing aspects of

Levels of object representation in anaclitic and introjective depression.

Abstract: (1974). Levels of Object Representation in Anaclitic and Introjective Depression. The Psychoanalytic Study of the Child: Vol. 29, No. 1, pp. 107-157.

Wages and Employment under Uncertain Demand

Abstract: This paper examines some implications of two postulates for firms' wage and employment policies. The first is that firms, or stockholders, have easier access to capital markets at lower costs or higher returns than do small investors, such as workers. Second, there are important mobility and turnover costs incurred when a worker moves from one firm to another. The existence of mobility costs means that the labour market is not a perfect market. Each firm is not restricted to taking as given some exogenous market wage, period by period, but has some amount of freedom about the wage strategy it sets. The firm cannot choose any wage-employment path it wishes, however, and I shall assume that in the long-run the firm must offer the same (expected) utility as that available elsewhere. In the short-run there is a constraint that the wage offer must never be so bad that all the firm's workers will quit and incur the mobility cost. There are solid grounds for believing that great differences exist between stockholders and workers with regard to capital markets. The majority of stocks are held by very wealthy persons indeed, who also hold almost all the state and local bonds and large proportions of the property and other assets.3 In addition, stockholders are frequently company executives or professionals with greater financial expertise and salaries many times that of the average industrial worker. The worker typically has a rather small net worth. His assets are durable goods and a rather small holding of money. He frequently has consumer credit liabilities outstanding.4 He also has much less knowledge of financial assets and institutions. A principal function of capital markets is to allow wealth-holders to diversify their holdings and so reduce the risk of their total portfolios. Stockholders, through their greater wealth and expertise, are much better able to bear risks than are workers.5 The difference in ability to bear risk between the two groups immediately suggests an opportunity to trade. In deciding what wage-employment strategy to set, the firm will be willing to reduce worker risk. By doing so, the firm is offering a joint product, employment plus an insurance or financial intermediation service. The firm does not do this simply because workers prefer it. Risk-reducing policies are the cheapest and hence most profitable way of attracting any given work-force. The choice of a risk-reducing policy by the firm will have an important impact on both the wage set and on employment variations-and hence the probability of unemployment. The firm will, in general, wish to reduce the uncertainty of the workers' incomes. An important feature of the model presented here is that the tendency of the firm to reduce risk has an asymmetrical effect on the wage strategy and on the employment strategy.

Learning Automata - A Survey

Abstract: Stochastic automata operating in an unknown random environment have been proposed earlier as models of learning. These automata update their action probabilities in accordance with the inputs received from the environment and can improve their own performance during operation. In this context they are referred to as learning automata. A survey of the available results in the area of learning automata has been attempted in this paper. Attention has been focused on the norms of behavior of learning automata, issues in the design of updating schemes, convergence of the action probabilities, and interaction of several automata. Utilization of learning automata in parameter optimization and hypothesis testing is discussed, and potential areas of application are suggested.

Classical direct interstring action

Abstract: We generalize the classical action-at-a-distance theory between point particles to include one-dimensionally extended objects (strings) in space-time. We build parametrization-invariant couplings which lead to equations of motion for strings in each others' influence. The direct coupling of the area elements of the world sheets of the strings is considered in detail, from which we define an antisymmetric adjunct field. We find that, for a given interaction, the nature of the forces depends on the type of strings involved, that is, open- vs closed-ended. Our coupling can be understood in terms of states appearing in the Veneziano and Shapiro-Virasoro models in 26 dimensions. However, we find an additional massive pseudovector field which arises from the interaction between the "Reggeon" and "Pomeron" sectors of this dual model.

Concept, word, and sentence: Interrelations in acquisition and development.

Abstract: Proposes a conceptual model to account for the child's initial translation of meanings into words. The model is discussed in terms of the characteristics of word acquisition and of the relation between 1st words and 1st sentences. While concept formation theory, semantic feature theory, and Piagetian theory are each alone inadequate to account for this process, each makes a necessary contribution to an adequate solution. The resulting model rests on the assumption that the young child translates the dynamic functional relations of objects into conceptual “core” meanings to which identificational features of concept instances are attached. It differentiates between the meaning of a concept and its referents and relates these to concept generation and concept identification, respectively. Some wider implications of the model for acquiring concepts and general semantic categories and for constructing sentences are briefly considered. (51 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

Acid Rain: A Serious Regional Environmental Problem

Abstract: At present, acid rain or snow is falling on most of the northeastern United States. The annual acidity value averages about pH 4, but values between pH 2.1 and 5 have been recorded for individual storms. The acidity of precipitation in this region apparently increased about 20 years ago, and the increase may have been associated with the augmented use of natural gas and with the installation of particle-removal devices in tall smokestacks. Only some of the ecological and economic effects of this widespread introduction of strong acids into natural systems are known at present, but clearly they must be considered in proposals for new energy sources and in the development of air quality emission standards.

Alternative Theories of Wage Determination and Unemployment in LDC's: The Labor Turnover Model

Abstract: The problem of unemployment and underemployment in LDC's has long been a central concern of development economics More recently, the discussion has focused on unemployment and underemployment in the urban sector The common diagnosis of the source of urban unemployment, particularly in economies such as those in East Africa where there does not seem to be "surplus labor" in the agricultural sector, is that there is a large wage differential between the urban and rural sectors that encourages migration into the urban sector And, finally, there seems to be a consensus that the remedies for this -if it is impossible in fact to lower the urban wage to the level in the rural sector -are (a) a wage subsidy to encourage private employers to hire more laborers (use more laborintensive techniques) and (b) the use of a shadow price of labor for projects in the government sector, which is lower than the market wage in the urban sector Although economists have advised governments all over the world to undertake these measures, they have based these policy prescriptions on partial equilibrium models that have not traced out the full implications of these policies; in particular, they have failed to take into account (a) the determination of the rate or level of unemployment in the economy and (b) the determination of wages in the urban sector The possible implications of these failures may easily be seen If the number of people in the urban sector is fixed,

T cell control of antibody production.

Abstract: The discovery that the thymus was involved in the development of the immune system (Miller, 1961; Archer et al, 1962; Jankovic et al, 1962) ushered in the “golden age of ‘thymology’” (Miller, 1967). A second golden age (Miller, 1967) began with the discovery that thymus-derived lymphocytes [soon to be christened T cells (Roitt et al, 1969)] did not themselves make circulating antibodies, but rather assisted other nonthymus-derived lymphocytes to do so (Miller and Mitchell, 1969; Davies, 1969; Claman and Chaperon, 1969). This second class of lymphocytes was christened B cells (Roitt et al, 1969), a term with sufficient ambiguity to gain the acceptance of those who thought these cells differentiated to a functional state in mammalian bone marrow and those who thought a mammalian equivalent of the bursa of Fabricius played a role in their differentiation.

Methane production in the interstitial waters of sulfate-depleted marine sediments.

Abstract: Methane in the interstitial waters of anoxic Long Island Sound sediments does not reach appreciable concentrations until about 90 percent of seawater sulfate is removed by sulfate-reducing bacteria. This is in agreement with laboratory studies of anoxic marine sediments sealed in jars, which indicate that methane production does not occur until dissolved sulfate is totally exhausted. Upward diffusion of methane or its production in sulfate-free microenvironments, or both, can explain the observed coexistence of measurable concentrations of methane and sulfate in the upper portions of anoxic sediments.

Metabolism of benzoate and the methylbenzoates by Pseudomonas putida (arvilla) mt-2: evidence for the existence of a TOL plasmid.

Abstract: Mutant strains of Pseudomonas putida (arvilla) mt-2 which have lost the ability to grow at the expense of m- or p-toluate (methylbenzoate) but retain the ability to grow with benzoate arise spontaneously during growth on benzoate; this genetic loss occurs to a lesser extent during growth on nonaromatic carbon sources in the presence of mitomycin C. The mutants have totally lost the activity of the enzymes of the divergent meta pathway with the possible exception of 2-oxopent-4-enoate hydratase and 4-hydroxy-2-oxovalerate aldolase; unlike the wild type they utilize benzoate by the ortho pathway. Evidence is presented that these mutants have lost a plasmid coding for the enzymes of the meta pathway, which may be transmitted back to them or into other P. putida strains. Preliminary results from these mutants and from a mutant defective in the regulation of the plasmid-carried pathway suggest that the wild type contains two benzoate oxidase systems, one on the plasmid which is nonspecific in both its catalysis and its induction and one on the chromosome which is more specific to benzoate as substrate and is specifically induced by benzoate.

Mechanisms of thermal acclimation to exercise and heat.

Abstract: By plotting local sweating rate from a given area against the central sweating drive (which is analogous to esophageal temperature, when mean skin temperature is constant), it is possible to determine the characteristic gain constant of that area as well as its point of zero central drive. An increase in the gain constant as a result of acclimation would indicate an increased sensitivity of the sweating mechanism per unit of central sweating drive, i.e., enhanced peripheral sensitivity. A displacement of the point of zero central drive as a result of acclimation would indicate that central mechanisms are responsible for the heightened sweating response. The study was undertaken to provide information about whether central or peripheral physiological mechanisms provide for increased sweating capabilities during acclimation, and about whether the increased sweating capabilities in heat acclimation and physical training are provided for by the same mechanisms.

Changes in axon fluorescence during activity: Molecular probes of membrane potential

Abstract: The fluorescence of dyes added to squid giant axons was studied during action potentials and voltage-clamp steps. One goal was to find fluorescence changes related to the increases in membrane conductance that underlie propagation. A second goal was to find large changes in fluorescence that would allow optical monitoring of membrane potential in neurons and other cells. Attempts were made to measure fluorescence changes using over 300 different fluorescent molecules and positive results were obtained with more than half of these. No evidence was found that would relate, any of the fluorescence changes to the increases in membrane conductance that accompany depolarization; most, instead, were correlated with the changes in membrane potential. The fluorescence changes of several dyes were relatively large; the largest changes during an action potential were 10−3 of the resting intensity. They could be measured with a signal-to-noise ratio of better than 10∶1 in a single sweep.

Minimum Wage Rates and the Pure Theory of International Trade

Abstract: Introduction, 98. — I. The minimum-wage economy, 99. — II. International equilibrium, 109. — III. Summary, 115.

Jaw movement and tooth use in recent and fossil primates.

Abstract: Masticatory movements and molar wear facets in species of Tupaia, Galago, Saimiri, and Ateles have been examined using cinefluorography and occlusal analysis. The molars have been compared with those of a fossil series: Palenochtha, Pelycodus and Aegyptopithecus. The extant primates are almost identical in their feeding behaviour, the movements and timing of the masticatory cycle. Food is first puncture-crushed where the cycle is elongated, the power stroke attenuated and abrasion facets are produced on the molars. Chewing follows, the movements are more complex, the power stroke has two distinct parts and attrition facets are produced. In the primitive forms (Tupaia, Palenochtha), shearing blades, arranged in series (en echelon) were used to cut the food during the first part (Phase I) of the power stroke as the lower teeth move into centric occlusion. This mechanism has been progressively replaced by a system of blade-ringed compression chambers which cut and compartmentalise the food in Phase I. This is followed by an anteromedially and inferiorly directed movement away from centric occlusion (Phase II) in which the food is ground. In both extant and fossil series there has been a clear trend towards the elongation of Phase II with a corresponding reduction in Phase I. These results suggest that the observed changes in the morphology of the jaw apparatus have probably occurred within the limits set by a pre-existing behavioral pattern.

Size and Scaling in Human Evolution

Abstract: Our general conclusion is simply stated: many lineages display phyletic size increase; allometric changes almost always accompany increase in body size. We cannot judge adaptation until we separate such changes into those required by increasing size and those serving as special adaptations to changing environments. In our view, the three australopithecines are, in a number of features, scaled variants of the "same" animal. In these characters, A. africanus is no more "advanced" than the larger, more robust forms. The one early hominid to show a significant departure from this adaptive pattern toward later hominids—cranially, dentally, and postcranially—is H. habilis from East Africa. The australopithecines, one of which was probably a precursor of the Homolineage, were apparently a successful group of basically vegetarian hominids, more advanced behaviorally than apes (87), but not hunter-gatherers. The fossil hominids of Africa fall into two major groupings. One probable lineage, the australopithecines, apparently became extinct without issue; the other evolved to modern man. Both groups displayed steady increase in body size. We consider quantitatively two key characters of the hominid skull: cranial capacity and cheek tooth size. The variables are allometrically related to body size in both lineages. In australopithecines, the manner of relative growth neatly meets the predictions for functional equivalence over a wide range of sizes (negative allometry of cranial capacity with a slope against body weight of 0.2 to 0.4 and positive allometry of postcanine area with a slope near 0.75). In the A. africanus to H. sapiens lineage, cranial capacity increases with positive allometry (slope 1.73) while cheek teeth decrease absolutely (slope — 0.725). Clearly, these are special adaptations unrelated to the physical requirements of increasing body size. We examined qualitatively other features, which also seem to vary allometrically. Of course, many characters should be studied quantitatively, but we think that the scheme outlined here should be treated as the null hypothesis to be disproved.