Showing papers by "Johns Hopkins University published in 1972"

Some Computer Organizations and Their Effectiveness

Abstract: A hierarchical model of computer organizations is developed, based on a tree model using request/service type resources as nodes. Two aspects of the model are distinguished: logical and physical. General parallel- or multiple-stream organizations are examined as to type and effectiveness?especially regarding intrinsic logical difficulties. The overlapped simplex processor (SISD) is limited by data dependencies. Branching has a particularly degenerative effect. The parallel processors [single-instruction stream-multiple-data stream (SIMD)] are analyzed. In particular, a nesting type explanation is offered for Minsky's conjecture?the performance of a parallel processor increases as log M instead of M (the number of data stream processors). Multiprocessors (MIMD) are subjected to a saturation syndrome based on general communications lockout. Simplified queuing models indicate that saturation develops when the fraction of task time spent locked out (L/E) approaches 1/n, where n is the number of processors. Resources sharing in multiprocessors can be used to avoid several other classic organizational problems.

Infant crying and maternal responsiveness.

Abstract: BELL, SILVIA M., and AINSWORTH, MARY D. SALTER. Infant Crying and Maternal Responsiveness. CHILD DEVELOPMENT, 1972, 43, 1171-1190. This naturalistic, longitudinal study of 26 infant-mother pairs shows that consistency and promptness of maternal response is associated with decline in frequency and duration of infant crying. By the end of the first year individual differences in crying reflect the history of maternal responsiveness rather than constitutional differences in infant irritability. Close physical contact is the most frequent maternal intervention and the most effective in terminating crying. Nevertheless, maternal effectiveness in terminating crying was found to be less powerful than promptness of response in reducing crying in subsequent months. Evidence suggests that whereas crying is expressive at first, it can later be a mode of communication directed specifically toward the mother. The development of noncrying modes of communication, as well as a decline in crying, is associated with maternal responsiveness to infant signals. The findings are discussed in an evolutionary context, and with reference to the popular belief that to respond to his cries "spoils" a baby.

Atmospheric Frontogenesis Models: Mathematical Formulation and Solution

Abstract: The approximation of geostrophic balance across a front is studied. Making this approximation, an analytic approach is made to a frontogenesis model based on the classic horizontal deformation field. Kelvin's circulation theorem suggests the introduction of a new independent variable in the cross-front direction. The problem is solved exactly for a Boussinesq, uniform potential vorticity fluid. Non-Boussinesq, non-uniform potential vorticity, latent heat, and surface friction effects are all studied. Using a two-region fluid we model the effects of confluence near the tropopause. A similar approach is made to the appearance of fronts in the finite-amplitude development of the simplest Eady wave; this is also solved analytically. Based on the surface fronts produced by these models, we give a general model of a strong surface front. There is a tendency to form discontinuities in a finite time.

Method of Lagrange multipliers for exploitation of the entropy principle

Abstract: In thermodynamics, whenever a material is subject to investigation of its properties, the entropy principle is used to impose restrictions on the constitutive relations for the material. There is not, so far, any simple method by which restrictions from the entropy principle can be derived for all kinds of different materials. Indeed, until very recently there was not even an entropy principle appropriate to all bodies. MULLER [1] [2] [3] has proposed such a general entropy principle, and here I suggest a simple method for its exploitation: the method of Lagrange multipliers. The entropy principle requires the constitutive relations to be such that every solution of the thermodynamic field equations satisfy the entropy inequality. To satisfy this requirement is not easy, since usually complicated calculations ensue. The method proposed here is intended to facilitate the solution of this problem. It can be described roughly as follows:

Rotational diffusion of rhodopsin in the visual receptor membrane.

Abstract: Transient photodichroism in the frog retina reveals that rhodopsin has a relaxation time of 20 µs. The site rhodopsin occupies in the membrane must therefore be highly fluid. This suggests rhodopsin may be a diffusional carrier.

Migration of a phthalate ester plasticizer from polyvinyl chloride blood bags into stored human blood and its localization in human tissues.

Abstract: A plasticizer, di-2-ethylhexyl phthalate, was found to be extracted from polyvinyl chloride plastic blood bags by both human and dog blood stored at 4°C at a rate of 0.25 ± 0.03 mg per 100 ml per day. Plasticizer was found in both the lipid-containing and lipid-free fractions of plasma whereas red cells contained only minor amounts. Seven of 12 lung-tissue samples taken at autopsy from patients who had received transfusions of stored blood contained detectable amounts of plasticizer. One patient, after open-heart surgery, excreted a urinary metabolite of the plasticizer in excess of the amount calculated to have been received in the transfused blood. The additional metabolite possibly came from plasticizer extracted from the polyvinyl chloride tubing of the cardiopulmonary unit. Although the toxicologic implications of these observations are not currently known, it is suggested that plastic formulations that do not contribute any extractable materials to blood or its fractions be developed.

Isotopic microassay of histamine, histidine, histidine decarboxylase and histamine methyltransferase in brain tissue.

Abstract: — Microassays are described for histamine, histidine, and the activities of the enzymes histidine decarboxylase (EC 4.1.1.22) and histamine niethyltransferase (EC 2.1.1.8) in brain tissue. The enzymic-isotopic microassay for histamine is based on the methylation of tissue histamine by added histamine methyl-transferase and [14C]- or [3H]-labelled S-adenosyl-l-methionine. In a double-isotopic form of the assay, a tracer of [3H]histamine is employed along with [14C]S-adenosyl-l-methionine, and the ratio [14C]:[3H] reflects the amount of histamine in the sample. Because the methylation of histamine is uniform in brain samples studied, a single isotopic assay with [3H]S-adenosyl-l-methionine as the methyl donor is possible and increases sensitivity, so that 10 pg of tissue histamine can be estimated reliably. The assay for histidine involves decarboxylation of histidine by a bacterial histidine decarboxylase and measurement of the histamine formed by the enzymicisotopic procedure. In the histidine decarboxylase assay, histamine synthesized from added histidine is measured. The assay for histamine methyltransferase involves measuring the formation of [14C]methylhistamine with [14C]S-adenosyl-l-methionine serving as the methyl donor.

Linear Dynamic Recursive Estimation from the Viewpoint of Regression Analysis

Abstract: A large class of useful multivariate recursive time series models and estimation methods has appeared in the engineering literature. Despite the interest and utility which this recursive work has when viewed as an extension of regression analysis, little of it has reached statisticians working in regression. To overcome this we (a) present the relevant random-β regression theory as a natural extension of conventional fixed-β regression theory and (b) derive the optimal recursive estimators in terms of the extended regression theory for a typical form of the recursive model. This also opens the way for further developments in recursive estimation, which are more tractable in the regression approach and will be presented in future papers.

Requirement for theta-bearing cells in lymphocytic choriomeningitis virus-induced central nervous system disease.

Abstract: THE immunopathological basis of the acutely fatal convulsive central nervous system (CNS) disease produced in adult mice following cerebral infection with lymphocytic Choriomeningitis (LCM) virus is well established1. Thus, a variety of immuno-suppressive treatments, given to adult mice inoculated intracerebrally with a potentially lethal dose of virus, produce a transient or permanent ablation of both the histological and clinical correlates of LCM. Permanently protected mice usually maintain high virus concentrations in their brains and blood for life2,3, presenting a picture which, on virological grounds, is strikingly similar to the lifelong virus carrier state arising in mice inoculated with LCM virus shortly after birth3,4.

Studies in interactive communication. I - The effects of four communication modes on the behavior of teams during cooperative problem-solving.

Abstract: Two-man teams solved credible, 'real-world' problems for which computer assistance has been or could be useful. Conversations were carried on in one of four modes of communication: (1) typewriting, (2) handwriting, (3) voice, and (4) natural, unrestricted communication. Two groups of subjects (experienced and inexperienced typists) were tested in the typewriting mode. Performance was assessed on three classes of dependent measures: time to solution, behavioral measures of activity, and linguistic measures. Significant and meaningful differences among the communication modes were found in each of the three classes of dependent variable. This paper is concerned mainly with the results of the activity analyses. Behavior was recorded in 15 different categories. The analyses of variance yielded 34 statistically significant terms of which 27 were judged to be practically significant as well. When the data were transformed to eliminate heterogeneity, the analyses of variance yielded 35 statistically significant terms of which 26 were judged to be practically significant.

Depression of growth in hyperactive children on stimulant drugs.

Abstract: In 29 hyperactive children, dextroamphetamine (10 or 15 mg per day) and methylphenidate (30 or 40 mg per day) caused suppression of weight gain. Mean yearly weight gain of nine children on...

Subtle consequences of methylmercury exposure, behavioral deviations in offspring of treated mothers.

Abstract: Overt neurological impairment is the endpoint currently used to document a case of methylmercury poisoning No consideration is given to possible subtle consequences Offspring from mice exposed to methylmercury on day 7 or 9 of pregnancy were apparently unaffected during postnatal development However, subtle behavioral differences between treated and control offspring were found when the overtly normal animals were tested in an open field and evaluated in a swimming apparatus at 1 month of age Brain weight, protein, choline acetyltransferase, and cholinesterase were not significantly altered

Equations Defining Abelian Varieties

Abstract: We shall start this chapter by proving “theta relations,” i.e., relations between theta functions. More precisely, we shall be interested in polynomial relations between θm(τ, z), θm(τ, 0) with constant coefficients. From the “labyrinth” of theta relations, we shall select just two, which are themselves not unrelated: The first one is called “Riemann’s theta formula” and the second one the “addition formula.” Their shortest proofs depend on the following lemma: Lemma 1. Let L denote a discrete commutative group and L1, L2 two subgroups of finite indices; let Φ denote an L1-function on L, i.e., a C-valued function on L such that the sum of ∣ Φ(ξ)∣ over L is convergent. Then we have $[L:{L_1}]\cdot \mathop\Sigma\limits_{\xi\epsilon{L_1}}\Phi(\xi) = \mathop\Sigma\limits_{\chi,\zeta} (\mathop\Sigma\limits_{\eta\varepsilon{L_2}} \chi(\eta + \zeta)\Phi((\eta + \zeta)),$ in which χ runs over the dual of L/L1 and ζ over a complete set of representatives of L/L2.

The Minimum Covering Sphere Problem

Abstract: The minimum covering sphere problem, with applications in location theory, is that of finding the sphere of smallest radius which encloses a set of points in En. For a finite set of points, it is shown that the Wolfe dual is equivalent to a particular quadratic programming problem and that converse duality holds. A finite decomposition algorithm, based on the Simplex method of quadratic programming, is developed for which computer storage requirements are independent of the number of points and computing time is approximately linear in the number of points.

Dark ionic flux and the effects of light in isolated rod outer segments.

Abstract: We have determined the permeability properties of freshly isolated frog rod outer segments by observing their osmotic behavior in a simple continuous flow apparatus. Outer segments obtained by gently shaking a retina are sensitive but nonideal osmometers; a small restoring force prevents them from shrinking or swelling quite as much as expected for ideal behavior. We find that Na+, Cl-, No3-, glycerol, acetate, and ammonium rapidly enter the outer segment, but K+, SO4=, and melezitose appear impermeable. The Na flux is rectified; for concentration gradients in the physiological range, 2 x 109 Na+ ions/sec enter the outer segment, but we detect no efflux of Na+, under our conditions, when the gradient is reversed. Illumination of the outer segment produces a specific increase in the resistance to Na+ influx, but has no effect on the flux of other solutes. This light-dependent Na+ resistance increases linearly with the number of rhodopsin molecules bleached. We find that excitation of a single rhodopsin molecule produces a transient (∼1 sec) "photoresistance" which reduces the Na+ influx by about 1%, thus preventing the entry of about 107 Na+ ions. At considerably higher light levels, a stable afterimage resistance appears which reduces the Na influx by one-half when 106 rhodopsin molecules are bleached per rod. We have incorporated these findings into a model for the electrophysiological characteristics of the receptor.

Acetylcholine receptors: number and distribution at neuromuscular junctions in rat diaphragm.

Abstract: The number of acetylcholine receptors per motor end plate in the rat diaphragm, measured by the binding of [(125)1]alpha-bungarotoxin, varies directly with rat size and is (4.0 +/- 0.2) x 10(7) for full-grown male rats. Autoradiographic analysis of single fibers labeled with this substance reveals that virtually all of these receptors are localized in the end plate.

Quantum yields of the luminol chemiluminescence reaction in aqueous and aprotic solvents

Abstract: — Quantum yields for luminol (3-aminophthalic hydrazide) chemiluminescence reactions fall into two classes depending on oxidizing conditions. In aprotic solvents the quantum yield is high and the excitation yield which allows for the fluorescence quantum yield of the product, is 0·09 and is unaffected by changes in solution temperature or polarity, or the presence of quenchers. In aqueous solution under optimum pH conditions (11–13), hydrogen peroxide oxidation results in a high chemiluminescence quantum yield with an excitation yield of 0·04 again unaffected by temperature, viscosity or quenchers. Other oxidizing conditions produce lower quantum yields probably by the introduction of competing chemical pathways. The luminol chemiluminescence light standard has been used to calibrate a spectrofluoro-meter with results in good agreement with the quantum yields of the ferrioxalate actinometer and the fluorescence of quinine sulfate and diphenylanthracene.

Criterion‐referenced applications of classical test theory 1,2

Abstract: A reliability coefficient for criterion-referenced tests is developed from the assumptions of classical test theory. This coefficient is based on deviations of scores from the criterion score, rather than from the mean. The coefficient is shown to have several of the important properties of the conventional normreferenced reliability coefficient, including its interpretation as a ratio of variances and as a correlation between parallel forms, its relationship to test length, its estimation from a single form of a test, and its use in correcting for attenuation due to measurement error. Norm-referenced measurement is considered as a special case of criterion-referenced measurement. What are criterion-referenced measures? According to Robert Glaser (1963) they are measures which "depend on an absolute standard of quality," as opposed to norm-referenced measures, which "depend on a relative standard." Glaser goes on to say that, for any individual student, "The degree to which his achievement resembles desired performance at any specified level is assessed by criterion-referenced measures." In other words, norm-referenced measures compare the student's performance with the mean of a norm group, whereas criterion-referenced measures compare his performance with a specified criterion score. In this paper, the term "criterion-referenced" will be used to refer to any test for which a criterion score is specified without reference to the distribution of scores of a group of examinees.3 This definition implies that all the items on the test must measure the same thingotherwise it makes no sense to specify a single criterion score. This means that if the test user is interested in measuring specific behaviors, all the items on the test must measure the same specific behavior. What constitutes a specific behavior is a question that the test user must answer for himself. For one test user it might be "solving arithmetic computation problems," for another it might be "solving multiplication problems," for another it might be "solving multiplication problems with a