Showing papers by "Stanford University published in 1976"

New Directions in Cryptography

Abstract: Two kinds of contemporary developments in cryptography are examined. Widening applications of teleprocessing have given rise to a need for new types of cryptographic systems, which minimize the need for secure key distribution channels and supply the equivalent of a written signature. This paper suggests ways to solve these currently open problems. It also discusses how the theories of communication and computation are beginning to provide the tools to solve cryptographic problems of long standing.

The Open-Field Test: a critical review.

Abstract: Over the w t 4 0 years Lhc open field bar ~ o l v e d a a commonly used tool for the rnmumcnt of animal behavior. Thh m i e w taka a dtical look at the we of I& instrument, u&y with regard to the development of a standard form for iu w. The variou procedura and .their sbortcomingr are 'dkmued, w i t h partimlar rcfupacc to the seemingly incooseguential detdk which have b.& showb to ioduhte open-field prformancc per w. Depndent paramrerr are considered both vith regard to their reliability and their validity for the measurement of such undul,ing mnstrucb as emotionality.

Some fundamental properties of speckle

Abstract: A speckle pattern formed in polarized monochromatic light may be regarded as resulting from a classical random walk in the complex plane. The resulting irradiance fluctuations obey negative exponential statistics, with ratio of standard deviation to mean (i.e., contrast) of unity. Reduction of this contrast, or smoothing of the speckle, requires diversity in polarization, space, frequency, or time. Addition of M uncorrelated speckle patterns on an intensity basis can reduce the contrast by 1/√M. However, addition of speckle patterns on a complex amplitude basis provides no reduction of contrast. The distribution of scale sizes in a speckle pattern (i.e., the Wiener spectrum) is investigated from a physical point of view.

Energy-selective reconstructions in X-ray computerized tomography.

Abstract: All X-ray computerised tomography systems that are available or proposed base their reconstructions on measurements that integrate over energy. X-ray tubes produce a broad spectrum of photon energies and a great deal of information can be derived by measuring changes in the transmitted spectrum. It is shown that for any material, complete energy spectral information may be summarised by a few constants which are independent of energy. A technique is presented which uses simple, low-resolution, energy spectrum measurements and conventional computerised tomography techniques to calculate these constants at every point within a cross-section of an object.

A functional analysis of circadian pacemakers in nocturnal rodents

Abstract: 1 Phase response curves for 15′ bright light pulses of four species of nocturnal rodents are described. All show delay phase shifts early in the subjective night, advance shifts in the late subjective night, and relative insensitivity during the subjective day. 2 The broad scatter in measured phase-shifts is largely due to error of measurement: the response of the pacemakers to light stimuli is more accurate than we observe. 3. Indications are found that the response to a resetting stimulus at a given phase of the rhythm is correlated with the individual\(\bar \tau \) (freerunning period). Fast pacemakers (short\(\bar \tau \)) tend to be more delayed or less advanced by the light than slow pacemakers (long\(\bar \tau \)). 4. Within individual mice (Mus musculus) the circadian pacemaker adjusts its resetting response to variations in its frequency: when τ is long (induced as after-effect of prior light treatment) light pulses at a defined phase of the oscillation (ct 15) produce smaller delay phase shifts than when τ is short. 5. Among species there are conspicuous differences in the shape of the phase response curve: where\(\bar \tau \) is long, advance phase shifts are large and delay phase shifts small (Mesocricetus auratus); where\(\bar \tau \) is short, advance shifts are small, and delay shifts are large (Mus musculus;Peromyscus maniculatus). 6. The functional meaning of the interrelationships of τ and PRC is briefly discussed.

Stationary and nonstationary learning characteristics of the LMS adaptive filter

Abstract: This paper describes the performance characteristics of the LMS adaptive filter, a digital filter composed of a tapped delay line and adjustable weights, whose impulse response is controlled by an adaptive algorithm. For stationary stochastic inputs, the mean-square error, the difference between the filter output and an externally supplied input called the "desired response," is a quadratic function of the weights, a paraboloid with a single fixed minimum point that can be sought by gradient techniques. The gradient estimation process is shown to introduce noise into the weight vector that is proportional to the speed of adaptation and number of weights. The effect of this noise is expressed in terms of a dimensionless quantity "misadjustment" that is a measure of the deviation from optimal Wiener performance. Analysis of a simple nonstationary case, in which the minimum point of the error surface is moving according to an assumed first-order Markov process, shows that an additional contribution to misadjustment arises from "lag" of the adaptive process in tracking the moving minimum point. This contribution, which is additive, is proportional to the number of weights but inversely proportional to the speed of adaptation. The sum of the misadjustments can be minimized by choosing the speed of adaptation to make equal the two contributions. It is further shown, in Appendix A, that for stationary inputs the LMS adaptive algorithm, based on the method of steepest descent, approaches the theoretical limit of efficiency in terms of misadjustment and speed of adaptation when the eigenvalues of the input correlation matrix are equal or close in value. When the eigenvalues are highly disparate (λ max /λ min > 10), an algorithm similar to LMS but based on Newton's method would approach this theoretical limit very closely.

Product Selection, Fixed Costs, and Monopolistic Competition

Abstract: Deals with a study which investigated the effects of fixed costs and monopolistic competition on the selection of products and product characteristics in a set of interacting markets. Price discrimination; Impact of monopolistic competition on complementary products; Approaches to the problems of substitute products. (Из Ebsco)

Computer Power and Human Reason

Abstract: I had some strong reactions to Joe Weizenbaum's book, Computer Power and Human Reason. The book mentions some important concerns which are obscured by harsh and sometimes shrill accusations against the Artificial Intelligence research community. On the whole, it seems to me that the personal attacks distract and mislead the reader from more valuable abstract points. I strongly recommend Samuel Florman's article "In Praise of Technology" in the November, 1975, issue of Harper's Magazine to see a different opinion about the role of technology in modern society.

Sex typing and the avoidance of cross-sex behavior.

Abstract: This article presents evidence for the hypothesis that cross-sex behavior is motivationally problematic for sex-typed individuals and that they actively avoid it as a result In particular, when asked to indicate which of a series of paired activities they would prefer to perform for pay while being photographed, sex-typed subjects were more likely than either androgynous or sex-reversed subjects to prefer sex-appropriate activity and to resist sex-inappropriate activity, even though such choices cost them money Moreover, actually engaging in cross-sex behavior caused sex-typed subjects to report greater psychological discomfort and more negative feelings about themselves

Doppler-Free Laser Polarization Spectroscopy

Abstract: We have demonstrated a sensitive new method of Doppler-free spectroscopy, monitoring the nonlinear interaction of two monochromatic laser beams in an absorbing gas via changes in light polarization. The signal-to-background ratio can greatly surpass that of saturated absorption. Polarization spectra of the hydrogen Balmer-$\ensuremath{\beta}$ line, recorded with a cw dye laser, reveal the Stark splitting of single fine-structure components in a Wood discharge.

Surface Brightness and Evolution of Galaxies

Abstract: It is well known that before the redshift-magnitude diagram of galaxies could be used for determination of the cosmological parameters one must know the evolution of the galaxies. We propose use of apparent surface brightness: which depends only on the redshift and is independent of the cosmological model and the inhomogeneities in the universe: for observational determination of the evolution of galaxies. The needed observations are isophotal angular diameters and apparent magnitudes within this or any other reasonable angular diameter. The application of the results for determination of q/sub 0/ is discussed briefly. (AIP)

Big Omicron and big Omega and big Theta

Abstract: Most of us have gotten accustomed to the idea of using the notation O(f(n)) to stand for any function whose magnitude is upper-bounded by a constant times f(n) , for all large n. Sometimes we also need a corresponding notation for lower-bounded functions, i.e., those functions which are at least as large as a constant times f(n) for all large n. Unfortunately~ people have occasionally been using the O-notation for lower bounds, for example when they reject a particular sorting method \"because its running time is O(n 2) \" I have seen instances of this in print quite of tent and finally it has prompted me to sit down and write a Letter to the Editor about the situation. The classical literature does have a notation for functions that are bounded below, namely ~(f(n)). The most prominent appearance of this notation is in Titchmarsh's magnum opus on Riemann's zeta function [8], where he defines ~(f(n)) on p. 152 and devotes his entire Chapter 8 to \"~-theorems\". See also Karl Prachar's Primzahlverteilung [7], P. 245. The ~ notation has not become very common, although I have noticed its use in a few places, most recently in some Russian publications I consulted about the theory of equidistributed sequences. Once I had suggested to someone in a letter that he use ~-notation \"since it had been used by number theorists for years\"; but later, when challenged to show explicit references, I spent a surprisingly fruitless hour searching in the library without being able to turn up a single reference. I have recently asked several prominent mathematicians if they knew what ~(n 2) meant, and more than half of them had never seen the notation before. Before writing this letter, I decided to search more carefully, and to study the history of O-notation and o-notation as well. Cajori's two-volume work on history of mathematical notations does not mention any of these. While looking for definitions of ~ I came across dozens of books from the early part of this century which defined O and o but not ~ .

The topographical distribution of S‐100 and GFA proteins in the adult rat brain: An immunohistochemical study using horseradish peroxidase‐labelled antibodies

Abstract: The cytological and topographical distribution of S-100 and glial fibrillary acidic (GFA) proteins in the adult rat brain has been compared using the horseradish peroxidase-labelled antibody technique. Both proteins are present in astrocytes and structures composed of astrocytic processes, namely the glial limitans and the perivascular membranes, but the cytological localization varies between the two proteins. S-100 is found in the nucleus and cytoplasm whereas GFA protein is confined to the cytoplasm. Neither is found in neurons, but S-100 is present in some oligodendroglia, suggesting a general regulatory role in glia. Although GFA protein in present in both protoplasmic and fibrous astrocytes, it is more prominent in the latter, confirming its association with astrocytic filaments.

The Joyless Economy: An Inquiry into Human Satisfaction and Consumer Dissatisfaction

Abstract: When this classic work was first published in 1976, its central tenet--more is not necessarily better--placed it in direct conflict with mainstream thought in economics. Within a few years, however, this apparently paradoxical claim was gaining wide acceptance. Scitovsky's ground-breaking book was the first to apply theories of behaviorist psychology to questions of consumer behavior and to do so in accessible, non-technical language. Setting out to analyze the failures of our consumerist lifestyle, Scitovsky concluded that people's need for stimulation is so vital that it can lead to violence if not satisfied by novelty--whether in challenging work, art, fashion, gadgets, late-model cars, or scandal. Though much of the book stands as a record of American post-war prosperity and its problems, the revised edition also takes into account recent social and economic changes. A new preface and a foreword by economist Robert Frank cover some of these issues. Two revised chapters discuss the assimilation of counter-cultural ideas throughout American society, especially ideas concerning the quality of life. Scitovsky draws fascinating connections between the new elite of college-educated consumers and the emergence of a growing underclass plagued by drugs and violence, perceptively tracing the reactions of these disparate groups to the problems of leisure and boredom. In the wake of the the so-called "decade of greed" and amidst calls for a "kinder, gentler" society, The Joyless Economy seems more timely than ever.

Self-reports versus sleep laboratory findings in 122 drug-free subjects with complaints of chronic insomnia.

Abstract: The authors compared the sleep laboratory recordings of 122 drug-free subjects who complained of chronic insomnia with the subjects' estimates of their habitual sleep characteristics and their estimated sleep time on the morning after sleeping in the laboratory. Most subjects consistently underestimated the amount of time they slept and overestimated the amount of time it took them to get to sleep in comparison with laboratory data. All subjects consistently underestimated the number of arousals they experienced. The authors discuss the implications of these findings for the treatment and definition of insomnia and for further research.

Sex typing and androgyny: further explorations of the expressive domain.

Abstract: Previous research by Bem has indicated that androgynous individuals of both sexes display "masculine" independence when under pressure to conform as well as "feminine" nurturance when interacting with a kitten. In contrast, sex-typed individuals were low in one or both of these behaviors. The two studies reported here were designed to replicate the low nurturance of the masculine male and to clarify the unexpected finding that feminine females were low in both independence and nurturance. In the first study subjects interacted with a human infant, and in the second study they listened to a lonely student. Taken together, the results of these two studies conceptually replicated the low nurturance of the masculine male and demonstrated that the low nurturance of the feminine female does not extend to her interaction with humans. Finally, evidence was presented in support of Spence, Helmreich, and Stapp's distinction between "androgynous" individuals, who are high in both masculinity and feminity, and "undifferentiated" individuals, who are low in both of these characteristics.

Statistical Thermodynamics of Random Networks

Abstract: Polymeric networks exhibiting high elasticity consist, typically, of linear chains several hundred bonds in length joined at their ends to $\phi $-functional junctions $(\phi >2)$. For random unconstrained chains of this length, the density distribution of chain vectors $r$ is Gaussian in satisfactory approximation. The chains interpenetrate copiously in the network; the domain described by the set of $\phi $ junctions that are topological neighbours of a given junction encompasses many (20-100) spatial neighbours. A phantom network is expressly defined as a hypothetical one whose chains may move freely through one another; the chains act exclusively by introducing a force that is proportional to the distance between each pair of junctions so connected. The following results of James & Guth are rederived for a Gaussian phantom network using a simplified version of their procedure: (1) the mean values $\overline{r}$ of the individual chain vectors are linear functions of the tensor $\lambda $ of the principal extension ratios specifying the macroscopic strain, (2) fluctuations $\Delta r=r-\overline{r}$ about these mean values are Gaussian, and (3) the mean-square fluctuations depend only on the structure of the network and not on the strain. Additionally, we show (4) that the distribution of the average vectors $\overline{r}$ is Gaussian, and (5) that $\langle (\Delta r)^{2}\rangle =(2/\phi)\langle r^{2}\rangle \_{0}$, a result obtained previously by Graessley. It follows from (1) and (3) that the transformation of chain vectors $r$ of the phantom network is not affine in $\lambda $, and hence that junctions exchange neighbours with strain. In real networks, the mutual interpenetration of chains pendent at a given junction must obstruct this process of local rearrangement of junctions; the transformation of chain vectors may therefore be more nearly affine in $\lambda $, especially when the network is undiluted. The elastic free energy derived for a phantom network of any functionality and degree of imperfection reduces to $\Delta A\_{\text{e1}}=\frac{1}{2}\xi kT(I\_{1}-3)$, where $I\_{1}$ = trace $(\lambda ^{T}\lambda)$ is the first invariant of the strain and $\xi $ is the cycle rank of the network. If the fluctuations of junctions in a real network are suppressed for the reasons stated, the elastic free energy is $\Delta A\_{\text{e1}}^{\ast}=\xi (1-2/\phi)^{-1}\frac{1}{2}kT(I\_{1}-3)-(2\xi /\phi)^{-1}kT$ln $(V/V^{0})$, where $V$ and $V^{0}$ are the actual and reference volumes, respectively. The expected trend from $\Delta A\_{\text{e1}}^{\ast}$ to $\Delta A\_{\text{e1}}$ with dilution may account, qualitatively at least, for the effect of dilution on the stress-strain relation. A similar trend with extension may explain the familiar departure of the observed tension-elongation relation from theory.

Sleep apnea in eight children.

Abstract: Eight children, 5 to 14 years of age, were diagnosed by means of nocturnal polygraphic monitoring with a sleep apnea syndrome similar to that seen in adults. Excessive daytime sleepiness, decrease in school performance, abnormal daytime behavior, recent enuresis, morning headache, abnormal weight, and progressive development of hypertension should suggest the possibility of a sleep apnea syndrome when any of these symptoms is associated with loud snoring interrupted by pauses during sleep. Surgery may eliminate the clinical symptomatology.

Observation of Stimulated Emission of Radiation by Relativistic Electrons in a Spatially Periodic Transverse Magnetic Field

Abstract: Gain has been observed for optical radiation at 10.6 \ensuremath{\mu}m due to stimulated radiation by a relativistic electron beam in a constant spatially periodic transverse magnetic field. A gain of 7% per pass was obtained at an electron current of 70 mA. The experiments indicate the possibility of a new class of tunable high-power free-electron lasers.

Effect of Human Leukocyte Interferon on Hepatitis B Virus Infection in Patients with Chronic Active Hepatitis

Abstract: Four patients with chronic hepatitis B infection and chronic active hepatitis were treated with human leukocyte interferon. Three of them had consistently elevated levels of circulating Dane-particle markers, including Dane-particle-associated DNA polymerase activity, hepatitis B core antigen and Dane-particle-associated DNA. Parenteral interferon administration at a dosage between 6.0 X 10(3) and 17 X 10(4) U per kilogram per day was associated with a rapid and reproducible fall in all Dane-particle markers in the three patients. The suppressive effect was transient when the interferon was given for 10 days or less but appeared to be more permanent when administration was prolonged for a month or more. In addition, long-term interferon therapy was associated with a marked fall in hepatitis B surface antigen in two of three patients and a disappearance of e antigen in two of two patients. Interferon may be useful in limiting carrier infectivity or eradicating chronic infection.

The Exchange Rate And The Balance of Payments In The Short Run and in The Long Run: A Monetary Approach

Abstract: This paper analyzes, by way of a dynamic model, the role of momentary asset equilibrium and expectations in the determination of the exchange rate in the short run, and the role of the process of asset accumulation in the determination of the time path from momentary to long-run equilibrium.

Transepithelial transport in cell culture

Abstract: In cell culture a kidney epithelial cell line MDCK, forms a continuous sheet of identically oriented asymmetrical cells joined by circumferential occluding junctions. The reconstructed epithelial membrane has transport and permeability qualities of in vivo transporting epithelia. The cell layer can be readily manipulated when cultured on a freely permeable membrane filter and, when placed in an Ussing chamber, electrophysiological measurements can be taken. In the absence of a chemical gradient, the cell layer generates an electrical potential of 1.42 mV, the apical surface negative. It is an effective permeability barrier and lacks significant shunting at the clamped edge, as indicated by a resistance of 84 ohms-cm2, which increased when bulk flow from basolateral to apical was induced by an osmotic gradient or electroosmosis. The MDCK cell layer is cation selective with a relative permeability ratio, PNa/PCl, of 1.7. Net water flux, apical to basolateral, was 7.3 mul cm-2 hr-1 in the absence of a chemical gradient. The morphological and functional qualities of a transporting epithelium are stable in cell culture, and the potential use of a homogeneous cell population in cell culture would enhance studies of epithelial transport at the cellular and subcellular levels.

The Rheological Properties of Suspensions of Rigid Particles

Abstract: Experimental and theoretical work on the rheological properties of suspensions are reviewed. Attention is focused on systems consisting of rigid, neutrally buoyant particles suspended in Newtonian fluids; no restrictions, however, are placed on the concentration of the particles or on the forces acting in the suspension. The assumption that an effective viscosity depending solely on the volume fraction of the particles suffices to describe the rheology of suspensions is examined and shown to be inadequate. Indeed, the experimental evidence strongly supports the view that suspensions behave macroscopically as non-Newtonian fluids whose rheological properties are influenced by a large number of factors; these factors are listed. The various theories that have been put forward to explain the flow of suspensions are discussed, with particular emphasis placed on the nature of the approximations made, so that purely empirical formulas can be clearly separated from those having a theoretical basis. Suggestions for future work, both theoretical and experimental, are provided.

Communication and Development The Passing of the Dominant Paradigm

Abstract: This article describes the dominant model of development, the factors that led to its decline in intellectual circles after about 1970, and the emerging alternatives. The implications of this academic shift in thinking on the role of communication in development are discussed in terms of such issues as the communication effects gap, the content of mass media messages about development, and the limitations of the social structure on developmental communication effects. Greater use of field experiments and network analysis is recommended.