Showing papers by "Yale University published in 1968"

A Theory of Conditionals

Abstract: A conditional sentence expresses a proposition which is a function of two other propositions, yet not one which is a truth function of those propositions I may know the truth values of “Willie Mays played in the American League” and “Willie Mays hit four hundred” without knowing whether or not Mays, would have hit four hundred if he had played in the American League This fact has tended to puzzle, displease, or delight philosophers, and many have felt that it is a fact that calls for some comment or explanation It has given rise to a number of philosophical problems; I shall discuss three of these

Probability of shock in the presence and absence of CS in fear conditioning.

Abstract: 2 experiments indicate that CS-US contingency is an important determinant of fear conditioning and that presentation of US in the absence of CS interferes with fear conditioning. In Experiment 1, equal probability of a shock US in the presence and absence of a tone CS produced no CER suppression to CS; the same probability of US given only during CS produced substantial conditioning. In Experiment 2, which explored 4 different probabilities of US in the presence and absence of CS, amount of conditioning was higher the greater the probability of US during CS and was lower the greater the probability of US in the absence of CS; when the 2 probabilities were equal, no conditioning resulted. Two conceptions of Pavlovian conditioning have been distinguished by Rescorla (1967). The first, and more traditional, notion emphasizes the role of the number of pairings of CS and US in the formation of a CR. The second notion suggests that it is the contingency between CS and US which is important. The notion of contingency differs from that of pairing in that it includes not only what events are paired but also what events are not paired. As used here, contingency refers to the relative probability of occurrence of US in the presence of CS as contrasted with its probability in the absence of CS. The contingency notion suggests that, in fact, conditioning only occurs when these probabilities differ; when the probability of US is higher during CS than at other times, excitatory conditioning occurs; when the probability is lower, inhibitory conditioning results. Notice that the probability of a US can be the same in the absence and presence of CS and yet there can be a fair number of CS-US pairings. It is this that makes it possible to assess the relative importance of pairing and contingency in the development of a CR. Several experiments have pointed to the usefulness of the contingency notion. Rescorla (1966) reported a Pavlovian 1This research was supported by Grants MH13415-01 from the National Institute of Mental Health and GB-6493 from the National Science Foundation, as well as by funds from Yale University.

Quasi-conformal mappings in $n$-space and the rigidity of hyperbolic space forms

Abstract: © Publications mathématiques de l’I.H.É.S., 1968, tous droits réservés. L’accès aux archives de la revue « Publications mathématiques de l’I.H.É.S. » (http:// www.ihes.fr/IHES/Publications/Publications.html) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/legal.php). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.

The relationship between body size of filter‐feeding cladocera and the maximum size of particle ingested

Abstract: The maximum size of plastic bead ingested by Bosmina Zongirustris and six species of Daphnia increased with increasing body size of the animals. The relationship between the diameter (,u) of the largest bead ingested ( y ) and carapace length (x, in mm) is given by an expression, y = 22x + 4.87. This relationship could be used to predict which members of a phytoplankton community would be available as food for different-sized -species of filter-feeding Cladocera.

Suture-Zones of Hybrid Interaction Between Recently Joined Biotas

Abstract: From a study of the geographic occurrences of contemporary hybridization among North American animals, it has become apparent that most of the hybrids are produced in a few relatively localized zones, with little hybridizing in the vast areas between these zones of mixing. The hybrids tend to be at least moderately fertile and therefore to be a source of significant gene exchange between the typically allopatric pairs of species and semispecies. There is a wide variety of consequences from this introgression, with greater or lesser influence on the parental populations, and large portions of the fauna and probably flora are involved. An appropriate term for such a belt of interfaunal and interfloral linkage is suture-zone.1

Oat‐cell carcinoma of the lung. Its origin and relationship to bronchial carcinoid

Abstract: Electron-microscopic examination of normal bronchial epithelium and mucous glands has revealed the presence of cells similar in appearance to Kultschitzky (argentaffin) cells in the intestinal canal. The cells, which possess long cytoplasmic processes, are present in small numbers at all levels of the bronchial tree and are found adjacent to the basement membrane. They contain characteristic cytoplasmic granules referred to as neurosecretory-type granules, which are similar to those present in intestinal argentaffin cells, adrenal medullary cells and sympathetic nerve endings. Eighteen bronchial carcinoid tumors and 22 oat-cell pulmonary cancers have also been found to contain similar neurosecretory-type granules in the tumor cell cytoplasm. On the basis of light-microscopic similarities and the production of similar common patterns of hormonal disturbances and the possession of similar ultramicroscopic features, it is suggested that oat-cell pulmonary cancer and bronchial carcinoid tumors are closely related. They may be, respectively, the malignant and locally malignant form of tumors derived from Kultschitzky-type cells normally found throughout the bronchial tree.

Sevier Orogenic Belt in Nevada and Utah

Abstract: In Nevada and Utah, sedimentation in the Cordilleran miogeosyncline began before the appearance of Cambrian fossils and continued without orogenic interruption through the Triassic. During the Jurassic, deformation and regional metamorphism occurred in the western part of the miogeosyncline, and the area of sediment accumulation shifted onto the Colorado Plateau. A major source of clastic material appeared along the eastern margin of the Cordilleran miogeosyncline in Early Cretaceous time; this source supplied the sediments that filled the Cretaceous to Paleocene Rocky Mountain geosyncline. Clasts in the Cretaceous conglomerates show an inverted stratigraphy, reflecting successive exposure of older and older rocks in an evolving orogenic belt along the eastern side of the Cordilleran miogeosyncline. This source area was the Sevier orogenic belt, which had a history of deformation through most of the Cretaceous (Sevier orogeny). Decollement thrusts with displacements of tens of miles are the characteristic structures of the belt, but several large folds are also known. The largest thrusts are overlain unconformably by uppermost Cretaceous conglomerates. Thrusting in the Sevier orogenic belt had virtually ceased by the time the Laramide orogeny began east of the Sevier belt in latest Cretaceous time. Laramide mountains were the result of uplift of great blocks of crystalline basement along nearly vertical, reverse, and steep thrust faults. The Uinta arch, which intersects the Sevier orogenic belt almost at a right angle, is the only one of these basement uplifts closely involved with the deformation of the Cordilleran miogeosyncline. North-south-trending regional normal faulting of post-Oligocene age has broken up the orogenic belt so that it is not immediately recognizable on geologic maps. Arch ranges, intrusive domes, and gravity slides are additional complications of the Tertiary geology, but widespread Tertiary deposits, particularly Oligocene ignimbrites, make a paleogeologic reconstruction possible; thus, the Sevier orogenic belt can be viewed as it existed before the normal faulting.

Tandem-Scanning Reflected-Light Microscope*

Abstract: Reflected-light microscopy of semitransparent material, such as unstained nervous tissue, is usually unsatisfactory because of low contrast and light scattering. In a new microscope both the object plane and the image plane were scanned in tandem so that only light reflected from the object plane was included in the image. The object was illuminated with nearly incoherent light passing through holes in one side of a rotating scanning disk (Nipkow wheel) which was imaged by the objective into the object plane. Reflected-light images of these spots were conducted to the opposite side of the same disk. Light could pass from the source to the object plane, and from the object to the image plane, only through optically congruent holes on opposite side of the rotating disk. The image obtained had better contrast and sharpness for some semitransparent material than possible in usual reflected-light microscopy.

Adaptive significance of pigment polymorphisms in colias butterflies. i. variation of melanin pigment in relation to thermoregulation.

Abstract: The identification of the selective forces acting on natural variation in a population of organisms may be a formidable task. Only a few such identifications have been made, as in the studies of Cain and Sheppard (1954 et seq., summarized by Ford, 1964) and others on polymorphism in Cepaea snails, or the studies of Kettlewell (summary: Kettlewell, 1961) on industrial melanism in moths. The wing pigmentation of pierid butterflies presents many opportunities for this sort of analysis. Much natural variation in this system has been noted in the genera Pieris and Colias (Bowden, 1961, 1963; Gerould, 1923; Remington, 1954). These insects deposite two kinds of pigment in their wing scales: melanin, which is black, and pteridines, which may be white, yellow, orange, or red. The wings of different Colias species may possess any of the latter shades as

Calculation of binding isotherms for heterogeneous polymers.

Abstract: The matrix method of statistical mechanics is used to calculate equilibria for the binding of small molecules to polymers. When there is only one kind of binding site the problem is simple; some examples are given for illustrative purposes. If, however, the binding sites are not all equivalent and the bound molecules interact or interfere with each other, the problem is no longer trivial, being formally analogous with calculation of the helix-coil transition equilibrium in a heterogeneous polypeptide. Particular difficulties arise when the sequence of binding sites is aperiodic; most naturally occurring materials fall in this class. The purpose of this paper is to point out that problems of this type are readily solved with good accuracy by use of random-number methods on a high-speed digital computer. One such calculation is presented for illustration. The methods developed are applicable to such systems as the binding of actinomycin, Hg- , and acridine dyes to DNA.

Lysergic Acid Diethylamide: Sensitive Neuronal Units in the Midbrain Raphe

Abstract: Units in areas of the midbrain rich in neurons containing serotonin respond to parenteral injections of d-lysergic acid diethylamide by a reversible cessation of spontaneous activity. The dose required is at or below threshold for gross behavioral effects. An inhibition of neurons containing serotonin after administration of d-lysergic acid diethylamide could account for the decreased metabolism of serotonin produced by this drug.

Cytotoxicity mediated by soluble antigen and lymphocytes in delayed hypersensitivity : iii. analysis of mechanism

Abstract: The cytopathic effect of lymph node cells from tuberculin-sensitized rats on rat embryo fibroblasts in the presence of PPD was not enhanced by admixture of normal (nonsensitized) lymph node cells. Preincubation studies showed that this in vitro response is initiated by the reaction of lymphocytes with specific antigen, beginning within 30 min, rather than uptake of antigen by the fibroblasts. The supernatant fluids from suspensions of sensitized cells incubated with PPD for 17 hr or more possessed cytotoxic activity. The target fibroblasts showed a marked increase in acid phosphatase content within 48 hr after the addition of sensitized lymph node cells and antigen.

Nutrient Loss Accelerated by Clear-Cutting of a Forest Ecosystem

Abstract: The forest of a small watershed-ecosystem was cut in order to determine the effects of removal of vegetation on nutrient cycles. Relative to undisturbed ecosystems, the cut ecosystem exhibited accelerated loss of nutrients: nitrogen lost during the first year after cutting was equivalent to the amount annually turned over in an undisturbed system, and losses of cations were 3 to 20 times greater than from comparable undisturbed systems. Possible causes of the pattern of nutrient loss from the cut ecosystem are discussed.

Vinblastine and griseofulvin reversibly disrupt the living mitotic spindle.

Abstract: Using polarized light we have studied the effects of various mitotic poisons on mitotic spindles of living Pectinaria oocytes; we have studied fixed specimens with phase and electron microscopy. Vinblastine caused attrition and eventual disappearance of spindle structure as rapidly as did colcemid, and subsequent recovery from this treatment was at least as fast as that from colcemid. Griseofulvin, however, was easily the best agent for rapid, reversible, and repeated dissolution of the spindle. Agents that arrest metaphase may act on nondividing cells by interfering with the organization of other gelated structures.

Sponge-feeding fishes of the West Indies

Abstract: In an analysis of the stomach contents of 212 species of West Indian reef and inshore fishes, sponge remains were found in 21 species. In eleven of these, sponges comprised 6% or more of the stomach contents; it is assumed that these fishes feed intentionally on sponges. Sponges comprise over 95% of the food of angelfishes of the genus Holacanthus, over 70% of the food of species of the related genus Pomacanthus, and more than 85% of the food of the filefish, Cantherhines macrocerus. Lesser quantities of sponges are ingested by the remaining fish species. Fishes that feed on sponges belong to highly specialized teleost families, suggesting that this habit has evolved in geologically late time. The small number of fish species that concentrate on sponges as food suggests that the defensive characters of sponges—mineralized sclerites, noxious chemical substances, and tough fibrous components—are highly effective in discouraging predation. The two sponges most frequently eaten by fishes have a low percentage of siliceous spicules relative to organic matter, but among the 20 next most frequently consumed species no striking correlation occurs with respect to spicule content. Color and form of the sponge show no special correlation with frequency of occurrence in fish stomachs. Three species of fishes appear to concentrate on one species of sponge, but in these cases over 60% of the food taken consists of a variety of other organisms. Those fishes, more than half of whose diet consists of sponges, tend to sample a wide variety of species. No strong evidence is provided by our data that fish predation is a significant factor in limiting sponge distribution in the West Indian region.

Calcium Carbonate Concretions Formed by the Decomposition of Organic Matter

Abstract: Bacterial decomposition of butterfish and smelts in small sealed jars containing seawater and other solutions, for periods ranging from 65 to 205 days, results in a large increase in concentrations of dissolved bicarbonate, carbonate, and ammonia (plus volatile amines). Accompanying this is a rise in pH and the precipitation of Ca(++) ion from solution. The Ca(++) is not precipitated as CaCO(3) but instead as a mixture of calcium fatty acid salts or soaps with from 14 to 18 carbon atoms. This can be explained by the thermodynamic instability of CaCO(3) relative to Ca soaps in the presence of excess free fatty acid. It is suggested that some ancient CaCO(3) concretions, especially those enclosing fossils of soft-bodied organisms, may have formed rapidly after death in the form of natural Ca soap (adipocere) which was later converted to CaCO(3).

The molecular basis for isozymes

Abstract: Proteins are always large molecules. Almost none have molecular weights of less than 10,000, and a few are polymerized aggregates with molecular weights of approximately one million. The number of amino acid residues required for the synthesis of such proteins varies from a low of about 100 to as many as 10,000. Not more than a few hundred amino acid residues are joined through peptide links to form a single chain, bu t several chains may associate to form large polymers. At one time it was believed tha t molecules of such large size might be subject to numerous mistakes in synthesis to yield a kind of microheterogeneity (Colvin et al., 1954). On this view a purified preparation of a protein would be an average mixture of many slightly different molecules. Our present understanding of protein synthesis renders this view implausible. Although mistakes in synthesis do occur, they appear to be insignificant in number. However, the primary polypeptide chain, once formed, is subject to many chemical modifications, particularly through the reactive amino, carboxyl, or hydroxyl groups of several of its amino acid residues. Disulfidebridging, hydrogen-bonding, and various other types of interaction between polypeptide chains all contribute to a secondary and tertiary threedimensional structure that may exist in several distinctive alternate conformations. In addition, most of the larger proteins are polymers of two or more polypeptide chains which may be identical or different. All these possibilities for affecting protein structure raise questions concerning the molecular homogeneity or heterogeneity of any particular protein preparation. How much variability does in fact exist, and what kind of variation can occur without changing the essential biological identity or physiological role of a protein a re questions tha t have been asked repeatedly and answered in accord with the knowledge and insights available a t the time. Moreover, the preparation of proteins for examination, their extraction and purification, have always led to the possibility of denaturation or changes of a purely artifactual nature. Biochemists have been very sensitive to such possibilities and have been reluctant t o conclude tha t heterogeneity in their finished preparations reflected a corresponding heterogeneity in the native state within the cell. This reserve has been reinforced by the strength of the one-gene-one-enzyme concept and by a recent appreciation of the precision of the molecular mechanisms of protein synthesis, all of which led to the expectation that each enzyme would generally be present in an organism in a single molecular form. Nevertheless, occasional claims were made for heterogeneity of single enzymes, but these had little impact until simple, easy methods for assessing

Heats of the helix–coil transitions of the poly A–poly U complexes

Abstract: The heats of the conformational transitions of poly (A + U) and poly(A + 2U) were determined in a twin-cell differential thermal analysis microcalorimeter capable of measuring heat effects of 25–35 meal, in reactions of this type, with a precision of about 3%. The dependence of these heats on the concentration of Na+ and K+ was studied and was found to be interpretable with fair success by a simple phenomenological argument which employs the concept of binding of counterions to polyelectrolytes.

Cytotoxicity mediated by soluble antigen and lymphocytes in delayed hypersensitivity. I. Characterization of the phenomenon.

Abstract: In the presence of specific antigen, lymph node cells from inbred rats with delayed hypersensitivity to tuberculoprotein, bovine gammaglobulin, and egg albumin produced progressive destruction of monolayers of rat embryo fibroblasts in tissue culture, first apparent at 48 hr and maximal at 72 hr. The effect was specific and did not depend on a genetic difference between the lymph node cells and target cells. It required antigen concentrations equal to or greater than 1.25 µg/ml and lymphocyte: target cell ratios of approximately 10 or 20:1. It could be evaluated both by a plaquing technique and by cell enumeration with an electronic particle counter.