Implausible Assumptions Research Articles

Effects of altering organ of Corti on cochlear distortion products f2 - f1 and 2f1 - f2.

1. Single cochlear nerve fiber recordings from unexposed chinchillas show spatial distributions of amplitude and phase of the distortion products f2 - f1 and 2f1 - f2 similar to those previously reported for the cat (35, 37, 42). 2. Damaging the organ of Corti in the region corresponding to the frequencies of a two-tone stimulus substantially reduces the amplitude of these distortion products at their characteristic places. 3. The distortion products 2f - f1 and 2f1 - f2 thus appear to be generated in the organ of Corti in the region of the primary-frequency places. 4. The neural responses suggest that the distortion products are propagated in the motion of the cochlear partition like externally applied stimulus tones at the distortion frequencies wih a similar spatial distribution of distortion product amplitude and phase. Models of the cochlea that assume nonlinear cochlear-partition dynamics can account for the similarity by demonstrating that distortion products generated by cochlear-partition nonlinearity can propagate apicalward in the motion of the cochlear partition. 5. Models of the cochlea using a linear-system model for cochlear partition motion, in cascade with a nonlinear transduction stage and a subsequent sharp filter, are inadequate to account for present observations, unless two currently implausible assumptions are made: a) stimulus tones near 4 kHz must propagate in normal cochleas at least as far apically as the 300-Hz place with sufficient amplitude to generate f2 - f1 there, and b) damage to the organ of Corti must interfere with this propagation of 4-kHz stimulus tones to the 300-Hz place. 6. Distortion generation in the cochlea is sensitive to delicate alterations of the organ of Corti. Short moderate-intensity exposures to sound can reversibly reduce the amplitudes of the distortion products f2 - f1 and 2f1 - f2 seen in responses from cochlear nerve fibers with characteristic frequencies (CF) near the distortion frequencies. Since such exposures do ot produce permanent structural changes visible under light microscopy, it seems most reasonable to believe that subtle changes in the organ of Corti (most likely in the hair cells themselves) in the region most responsive to f1 and f2 reduce the generation of mechanically present distortion products.

Tilting Toward Thanatos: America's “Countervailing” Nuclear Strategy

America's current nuclear strategy seeks to improve deterrence with a counterforce targeting plan that exceeds the requirements of mutual assured destruction. This “countervailing” nuclear strategy codifies an enlarged spectrum of retaliatory options. The author argues, however, that the countervailing strategy is based upon a number of implausible and contradictory assumptions, and that it actually degrades the overriding objective of genuine security. For many reasons, the Soviet Union is not apt to assign a higher probability of fulfillment to American counterforce threats; under certain conditions, current policy confronts our adversary with a heightened incentive to pre-empt. The conclusion identifies an alternative strategy for the avoidance of nuclear war, a network of doctrines and obligations that calls for a return to minimum deterrence, a comprehensive test ban, and a joint renunciation of the right to the first use of nuclear weapons.

The Ecological Context of Urban Crime

This article tests further a relationship between suburbanization and central-city crime rates shown in papers by Gibbs and Erickson (1976) and by Skogan (1977). We show that although Gibbs and Erickson fail to introduce an important control (metropolitan population), the relationship persists after such a control is introduced. We also show that the relationship holds for a much wider range of cities than the 32 large cities studied by Skogan. Differing explanations of the relationship offered by Gibbs and Erickson and by Skogan are evaluated. The Gibbs and Erickson explanation involves implausible assumptions about movement of crime participants from suburbs to cities. The relationship is more likely explained on the basis of urban-suburban status differentials and central-city decline, both of which are maximized in larger, older, more suburbanized cities.

Solvent accessibility, protein surfaces, and protein folding

Studies of the native structures of proteins, together with measurements of the thermodynamic properties of the transition between unfolded and native states, have defined the major components of the forces that stabilize native protein structures. However, the nature of the intermediates in the folding process remains largely hypothetical. It is a fairly widespread and not implausible assumption that the intermediates in the folding of a monomeric protein contain the same kinds of secondary and tertiary structures that appear in the native conformation, and that, although unstable, their lifetimes are prolonged by forces similar to those that stabilize the native structure. We wished to examine what happens if, during the folding of a monomeric protein, regions of secondary structure come together to form an intermediate of reduced instability. We applied calculations of accessible surface area (a measure of hydrophobic stabilization) and parameterized nonbonded energy calculations (measuring the strengths of van der Waals forces) to identify the kinds of stabilizing interactions that might be available to such an intermediate. First, we analyzed the total buried surface area of two types of proteins into contributions from formation of secondary structure alone, interaction of pairs of secondary-structural elements, the formation of the structure alone, interaction of pairs of secondary-structural elements, the formation of the complete secondary structure without the turns, and the complete native structure. The formation of secondary structure alone, without tertiary-structural interactions, buries roughly half the surface that the complete structure does. We then analyzed in more detail the approach of two alpha-helices to form a complex, as an illustrative example of the nature of the interaction between compact structural units which remain fairly rigid during their interaction. Many features of the results are not limited to the interaction of alpha-helices. (The results therefore neither confirm nor refute the hypothesis that alpha-helices are intermediates in the folding proteins). We find that the first forces to be felt upon approach arise from solvent conditions on the relative position and orientation of the two helices as does the close packing which optimizes the van der Waals interactions at shorter distances apart. Therefore there appears to be a range of distances in which hydrophobic interactions could create a nonspecific complex between two helices in which the side chains might have sufficient time to seek the proper interdigitation observed in the native structure, where the two helices are in intimate contact. Indeed, we find that only in the final stages of approach is the native geometry the most stable; in the region in which solvent-exclusion forces predominate, the conformation with helix axes parallel is more stable than the native conformation, in the cases we examined...

The gain from free trade under conditions of uncertainty

It is argued that recent attempts to demonstrate that free trade may be harmful under some kinds of uncertainty are based on implausible assumptions. It is shown also that standard proofs of the gainfulness of free trade can be adapted to accommodate uncertainty.

Nonseparability and the voluntary approach to externality problems

Ronald Coase asserted that voluntary two-party bargaining with zero transaction costs results in an optimal resource allocation, which is invariant with respect to the liability rule. It has been argued that nonseparabilities destroy the validity of Coase's theorem. In this paper it is shown that this criticism is based on implausible assumptions about the externality-receivers adjustment to the externality level.

Paths of association in epidemiological analysis: application to health effects of environmental exposures.

Conventional regression analysis is based on assumptions of bidirectional associations between pairs of independent variables. In a number of circumstances these assumptions are not plausible. Structural representation in conventional regression is based on a set of parallel paths between independent and dependent variables; when the implausible assumptions are excluded, a different structrual relation between the independent and dependent variables is found. It permits a series associative path between independent variables. Two criteria for modification of conventional multivariate analysis are presented. They are when bilateral symmetry among independent variables is implausible on the basis of a priori information, and when there are significant differences between zero order and first order partial correlation coefficients. When these criteria are applied, there may result a series-parallel matrix of associations. For analysis of such a matrix, the procedures of path analysis are appropriate. The concepts are illustrated with environmental examples, and path analytical computations are worked out for a set of data on social and environmental factors which affected infant mortality in England and Wales between 1928-1938.

Genetic activity of sex chromosomes in germinal cells.

If I adhere strictly to the title proposed for me and speak only of the genetic activity of the sex chromosomes in germ cells, there is very little to say. The evidence is necessarily indirect and includes, first, examples of differential behaviour of germ cells of different sex chromosome constitution in situations where competitive proliferation is a possibility, as in some mosaics and chimaeras; and secondly, exceptional species in which the sex chromosome constitution is normally different in germ cells and soma. The species concerned are all mammals. An instance of the first kind is provided by observations made on a 39,X /41,XYY mosaic mouse discovered by chance in the course of an irradiation experiment (Evans, Ford & Searle 1969). All the spermatogonia and spermatocytes examined contained 41 chromosomes, including two Y chromosomes, whereas bone marrow (the only other tissue examined) was mosaic, the probability of difference being due to sampling error being very low. The question, then, was whether the failure to detect mosaicism among the germ cells was a consequence of chance exclusion of the 39, X cell type from the germ line during development, or of differential proliferation and/or survival of 41,XYY germ cells in the testicular environment. The latter interpretation was favoured on the grounds: (1) A 39,X /41,XYY mosaic is likely to have originated by non-disjunction of the Y chromosome at the first cleavage division of a 40,XY zygote, since other theoretically possible modes of origin would require the combination of rare events or other implausible assumptions. (2) Primordial germ cells of the constitution 39, X are capable of reaching the developing gonad and subsequently forming functional oocytes as evidenced by the fertility of 39, X female mice (Russell, Russell & Gower 1959). (3) Nearly all half-and-half coat colour mosaic mutants are also germ cell mosaics (Russell 1964), implying that when two distinct cell lines are present very early in development both lines are likely to be represented among the germ cells

The Effects of Taxation on Risk Taking

The proposition that a proportional tax with full loss offset increases personal taking is now widely accepted by professional economists. This conclusion, originally suggested by Domar and Musgrave (1944), has more recently been reached by several economists working in context of von Neumann-Morgenstern expected-utility maximization (Tobin 1958; Hall 1960; Richter 1960; Penner 1964). A heuristic argument to reconcile this rather surprising result with intuition would be something like this. Because imposition of a tax decreases both yield and risk of all assets, it increases investor's demand for higher yield (raises the utility of income) and reduces his resistance to assuming more (lowers marginal disutility of risk). If tax lowers yield and of every security in same proportion (as occurs with yield and measures considered by previous writers), market risk-yield rate of transformation is unchanged. The result is an increased demand by investors for higher yielding and more risky assets. The purpose of this paper is to demonstrate that assertion that proportional taxation causes individuals who maximize expected utility' to increase taking is not generally true. Section I shows that previous attempts to prove that taxation increases taking have relied on a variety of restrictive and implausible assumptions. Section II then argues that concept of taking (and therefore of tax base) should be extended beyond portfolio choice and, in this framework, offers a counter-example to general proposition that taxation increases taking.

Nature of the Anomalous Resonance in the Ferromagnet K2CuCl4·2H2O

An anomalous magnetic resonance observed in ferromagnetic K2CuCl4·2H2O with the microwave and dc magnetic fields parallel, was tentatively interpreted as a forbidden hyperfine resonance involving simultaneous electron and nuclear spin flips. A theory explaining many of the observed features has been proposed. The theory depended, however, on the somewhat implausible assumption that the FMR relaxation time was dominanted by a term proportional to the third power of the magnon wavevector. In order to check this assumption, and to re-examine the unusual frequency dependence reported for the ratio of the forbidden to allowed intensities (ν4±1), extensive measurements were made at several microwave frequencies on samples of varying shapes and sizes. We found, surprisingly, that at a given frequency the intensity ratio was a function of the sample size, with the intensity of the forbidden line changing much more rapidly than the sample volume. In addition, the spacing between the forbidden and allowed lines, predicted to be a measure of the hyperfine interaction, was found to be a function of the sample shape. From these findings and additional evidence presented, it is concluded that the data can be more fully explained on the assumption that the anomalous forbidden resonance is in fact the (2, 1, 0) magnetostatic mode.

Some Behavioral Aspects of Cooperative Bargaining in Agriculture

B ARGAINING power for farmers currently is receiving attention from numerous groups who are concer ed about the price a d i come problems facing U. S. commercial agriculture. In spite of considerable experience with collective bargaining in agriculture, a paucity of information exists on the process by which cooperative bargaining associations attempt to enhance the economic returns of their member producers. This paper explores some of the behavioral aspects of cooperative bargaining in agriculture. Since the bilateral monopoly model was developed over a century ago, economists have attempted to resolve the bargaining problem by using conventional economic analysis [5]. Game theorists took up the task of developing meaningful bargaining theories in the 1940's [3]. Both approaches contain a major weakness: the implausible assumptions on which they are based. Helmberger and Hoos recently developed a theory of cooperative bargaining in which they identify the boundaries of price and quantity under various market structure assumptions [4, pp. 50-63]. However, none of the existing theories give much insight into the bargaining process as it occurs in the sale of farm products to processors.

Economic Planning and Data Requirements

PLANNING will be taken here to mean both drawing up a plan of action and implementing it. Sometimes one may mean by planning simply that one is intending to do something, e.g. one may speak of planning to go to China for one's holiday. But when talking about a planned one usually means an economy in which plans are implemented, not one in which people are sitting around drawing up paper plans as a sort of mental therapy. A plan is thus a plan of action. As such it is to be sharply distinguished from a mere forecast. But like any other form of plan, such as a military plan of battle, the plan of action will depend on a whole range of forecasts, assumptions, guesses, etc. To some extent one may take risks. For example, one may set one's targets in one particular field higher rather than lower, even though the achievement of such a target may depend partly on the realization of an assumption for which there is very little evidence, on the grounds that the losses from such a course of action, if the critical assumption were not realized, will be small compared with the gains accruing if it were, or that luck regarding this particular assumption can be offset by good luck elsewhere. This procedure is perfectly rational, up to a point. A plan may be bad because it relies too much on luck, wishful thinking and implausible assumptions. That is, it sets its sights too high, given the available information and instruments of action. But a plan may also be in the opposite sense, namely by failing to set its targets high enough, or by failing to take advantage of possibilities of reducing uncertainty. Before judging a plan, however, one must also allow for the time period over which the plan is supposed to operate. In planning to-morrow's operations the number much of unknowns is relatively small. But the constraints on one's own actions are also greater. In planning for the next ten or twenty years the unknowns are much greater, but the scope for influencing some of the relevant variables may also be much greater. This greater scope means that the plan can have a more optimalization character. Thus planning involves the art of striking the right balance between the greater possibilities of action that is more daring or on a more grandiose scale-particularly time scale-and the risks involved in basing one's plans on unknown variables. In any concrete situation much will depend on the sort of data available, as well as on hosts of other factors. This is why very few valid generalizations about planning can be made, and those which are possible are trivial. This is where we come, at last, to those aspects of planning that are presumably of most interest to this Society, namely the availability of the sort of statistics that planners need.

Radar reflectivity of storms containing spongy hail

Experimental measurements at 5-cm wavelength show that the backscattering cross sections of ice spheres approximately 2 cm in diameter which are coated with a mixture of water and ice (‘spongy’ coating) are 3 to 4 db above that of the equivalent all-water spheres and at least 10 db above that of the equivalent solid ice spheres. Thus it is shown that the extremely large reflectivity factor at 3-cm wavelength (Ze = 107 mm6 m−3) observed for hailstones can be accounted for with concentrations of only about 3 g m−3 of 1-cm-diameter hailstones which have a spongy coating. Both the falling away of the spongy coating upon melting and its freezing upon being lifted in the updraft will cause reductions in reflectivity, thereby producing the maximum reflectivity observed at an intermediate level of the storm. The existence of spongy ice allows the surface and radar observations of hailstorms to be explained without any of the physically implausible assumptions of previous hypotheses.