Showing papers by "California Institute of Technology published in 1978"
TL;DR: In this article, the influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition and found that the variability of the relationship between the δ(15)N values of animals and their diets is greater for different individuals raised on the same diet than for the same species raised on different diets.
5,562 citations
TL;DR: The wild-type and mutant segmentation patterns are consistent with an antero-posterior gradient in repressor concentration along the embryo and a proximo-distal gradient along the chromosome in the affinities for repressor of each gene's cis-regulatory element.
Abstract: The bithorax gene complex in Drosophila contains a minimum of eight genes that seem to code for substances controlling levels of thoracic and abdominal development. The state of repression of at least four of these genes is controlled by cis-regulatory elements and a separate locus (Polycomb) seems to code for a repressor of the complex. The wild-type and mutant segmentation patterns are consistent with an antero-posterior gradient in repressor concentration along the embryo and a proximo-distal gradient along the chromosome in the affinities for repressor of each gene's cis-regulatory element.
3,520 citations
TL;DR: In this article, a data set comprising 110 spreading rates, 78 transform fault azimuths and 142 earthquake slip vectors was inverted to yield a new instantaneous plate motion model, designated RM2.
Abstract: A data set comprising 110 spreading rates, 78 transform fault azimuths and 142 earthquake slip vectors was inverted to yield a new instantaneous plate motion model, designated RM2. The mean averaging interval for the relative motion data was reduced to less than 3 My. A detailed comparison of RM2 with angular velocity vectors which best fit the data along individual plate boundaries indicates that RM2 performs close to optimally in most regions, with several notable exceptions. On the other hand, a previous estimate (RM1) failed to satisfy an extensive set of new data collected in the South Atlantic Ocean. It is shown that RM1 incorrectly predicts the plate kinematics in the South Atlantic because the presently available data are inconsistent with the plate geometry assumed in deriving RM1. It is demonstrated that this inconsistency can be remedied by postulating the existence of internal deformation with the Indian plate, although alternate explanations are possible.
2,005 citations
TL;DR: The fact that the general decoding problem for linear codes and the general problem of finding the weights of a linear code are both NP-complete is shown strongly suggests, but does not rigorously imply, that no algorithm for either of these problems which runs in polynomial time exists.
Abstract: MEMBER, IEEE, AND HENK C. A. V~ TILBORG The fact that the general decoding problem for linear codes and the general problem of finding the weights of a linear code are both NP-complete is shown. This strongly suggests, but does not rigorously imply, that no algorithm for either of these problems which runs in polynomial time exists.
1,541 citations
TL;DR: A procedure for eucaryotic structural gene isolation which involves the construction and screening of cloned libraries of genomic DNA is presented and Restriction mapping and hybridization studies reveal the presence of closely linked beta-globin genes.
1,516 citations
TL;DR: In this article, the authors discuss how present experiments can put limits on their production, and discuss how to limit the number of gluons that can be produced in the future.
1,136 citations
TL;DR: In this paper, it was demonstrated that differences in the Ca/^(44)Ca ratio due to mass dependent isotope fractionation in nature are clearly resolvable to a level of 0.001.
892 citations
TL;DR: The two independently isolated β-globin clones differ from each other by the presence of a Pst I restriction enzyme cleavage site within the large intervening sequence of the δ- globin gene of one of the clones, which suggests that the human DNA carried in the two clones was derived from two homologous chromosomes which were heterozygous for the PstI restriction enzyme recognition sequence.
850 citations
TL;DR: In this article, the possibility of using Bragg reflection in a cylindrical fiber to obtain lossless confined propagation in a core with a lower refractive index than that of the cladding medium is proposed and analyzed.
Abstract: The possibility of using Bragg reflection in a cylindrical fiber to obtain lossless confined propagation in a core with a lower refractive index than that of the cladding medium is proposed and analyzed.
833 citations
TL;DR: The work described here is still in progress as discussed by the authors, hence this paper will be a brief sampling of the results to date, as well as a summary of the work described in this paper.
Abstract: The work described here is still in progress; hence this paper will be a brief sampling of the results to date.
811 citations
23 Aug 1978
TL;DR: In this paper, a method of using a texturing function to perform a small perturbation on the direction of the surface normal before using it in the intensity calculations is presented.
Abstract: Computer generated shaded images have reached an impressive degree of realism with the current state of the art. They are not so realistic, however, that they would fool many people into believing they are real. One problem is that the surfaces tend to look artificial due to their extreme smoothness. What is needed is a means of simulating the surface irregularities that are on real surfaces. In 1973 Ed Catmull introduced the idea of using the parameter values of parametrically defined surfaces to index into a texture definition function which scales the intensity of the reflected light. By tying the texture pattern to the parameter values, the texture is guaranteed to rotate and move with the object. This is good for showing patterns painted on the surface, but attempts to simulate rough surfaces in this way are unconvincing. This paper presents a method of using a texturing function to perform a small perturbation on the direction of the surface normal before using it in the intensity calculations. This process yields images with realistic looking surface wrinkles without the need to model each wrinkle as a separate surface element. Several samples of images made with this technique are included.
TL;DR: In this article, a model of the properties of the jet of mesons generated by a fast outgoing quark is presented, where the meson that contains the original quark leaves momentum and flavor to a remaining jet in which the particles are distributed like those of the original jet.
TL;DR: It has been possible to determine the mean age of sediment provenances, as studies of sedimentary rocks suggest that the samarium-neodymium isotopic system is not substantially disturbed during sedimentation or diagenesis.
Abstract: Samarium-neodymium and rubidium-strontium isotopic systematics together with plausible assumptions regarding the geochemical evlution of continental crust material, have been used to ascertain the times at which segments of continental crust were formed. Analyses of composites from the Canadian Shield representing portions of the Superior, Slave, and Churchill structural provinces indicate that these provinces were all formed within the period 2.5 to 2.7 aeons. It has been possible to determine the mean age of sediment provenances, as studies of sedimentary rocks suggest that the samarium-neodymium isotopic system is not substantially disturbed during sedimentation or diagenesis.
TL;DR: In this article, the concept of sacrificial barrier is introduced, which is based on an irreversible loss of barrier material by interfacial reactions with the adjoining metals, and successful applications are presented.
02 May 1978
TL;DR: In this article, an efficient numerical method is developed for solving nonlinear wave equations typified by the Korteweg-de Vries equation and its generalizations, using a pseudospectral (Fourier transform) treatment of the space dependence together with a leap-frog scheme in time.
Abstract: An efficient numerical method is developed for solving nonlinear wave equations typified by the Korteweg-de Vries equation and its generalizations. The method uses a pseudospectral (Fourier transform) treatment of the space dependence together with a leap-frog scheme in time. It is combined with theoretical discussions in the study of a variety of problems including solitary wave interactions, wave breaking, the resolution of initial steps and wells, and the development of nonlinear wavetrain instabilities.
TL;DR: In this paper, the authors developed a thin plate theory in which transverse shear strains are accounted for, and the variables in the theory are all kinematic, namely, displacements and independent rotations.
TL;DR: Amorphous layers, approximately 4000 A thick, were formed on single-crystal Si samples by implantation of 28Si ions at LN2 substrate temperature as mentioned in this paper, where channeling effect measurements with MeV 4He ions were used to measure the thickness of the amorphous layers and to measure subsequent epitaxial regrowth on the underlying crystalline substrates.
Abstract: Amorphous layers, approximately 4000 A thick, were formed on single‐crystal Si samples by implantation of 28Si ions at LN2 substrate temperature. Channeling‐effect measurements with MeV 4He ions were used to measure the thickness of the amorphous layers and to measure the subsequent epitaxial regrowth on the underlying crystalline substrates. For annealing temperatures between 450 and 575 °C, the growth rate showed a strong dependence on the substrate orientation with 〈100〉‐oriented samples exhibiting about a 25 times higher growth rate than 〈111〉‐oriented samples. Measurements of the growth rate on a series of samples cut in 5° angular increments show that there is a monotonic decrease from the 〈100〉 to the 〈111〉 orientation. A simple model is proposed to explain the observed orientation dependence.
02 May 1978-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: An efficient numerical method is developed for solving nonlinear wave equations typified by the Korteweg-de Vries equation and its generalizations using a pseudospectral (Fourier transform) treatment of the space dependence together with a leap-frog scheme in time.
Abstract: An efficient numerical method is developed for solving nonlinear wave equations typified by the Korteweg-de Vries equation and its generalizations. The method uses a pseudospectral (Fourier transform) treatment of the space dependence together with a leap-frog scheme in time. It is combined with theoretical discussions in the study of a variety of problems including solitary wave interactions, wave breaking, the resolution of initial steps and wells, and the development of nonlinear wavetrain instabilities.
TL;DR: In this paper, nonlinear optical mixing can be used to perform a variety of new optical functions, as well as real-time holography, and the theory and some of the first experiments are described.
Abstract: Nonlinear optical mixing can be used to perform a variety of new optical functions, as well as real-time holography. The theory and some of the first experiments are described.
TL;DR: In this article, a set of rotationally invariant observables which characterizes the shapes of events is presented, and is calculable in quantum-chromodynamics perturbation theory for final states consisting of quarks and gluons.
Abstract: We present a set of rotationally invariant observables which characterizes the "shapes" of events, and is calculable in quantum-chromodynamics perturbation theory for final states consisting of quarks and gluons ($G$). We include the effects of fragmentation to hadrons in comparing the shapes of events from the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}G$, and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{heavy}\mathrm{resonance}\ensuremath{\rightarrow}\mathrm{GGG}$, and from heavy-quark and lepton production. We indicate how our analysis may be extended to deep-elastic lepton-hadron interactions and hadron-hadron collisions involving large transverse momenta.
TL;DR: This paper found that auditory units that responded to sound only when it originated from a limited area of space were found in the lateral and anterior portions of the midbrain auditory nucleus of the owl (Tyto alba).
Abstract: Auditory units that responded to sound only when it originated from a limited area of space were found in the lateral and anterior portions of the midbrain auditory nucleus of the owl (Tyto alba). The areas of space to which these units responded (their receptive fields) were largely independent of the nature and intensity of the sound stimulus. The units were arranged systematically within the midbrain auditory nucleus according to the relative locations of their receptive fields, thus creating a physiological map of auditory space.
01 Jan 1978
TL;DR: In this article, the effects of obliquity on crater size, shape, and ejecta distribution were analyzed using laboratory studies of hypervelocity impacts against rock and particulate media.
Abstract: Meteoritic materials most probably impact planetary bodies along oblique trajectories inclined less than 45 deg above their surfaces. Laboratory studies of hypervelocity impacts against rock and particulate media are presented that indicate important effects of obliquity on crater size, shape, and ejecta distribution. The effects are particularly important to crater size-frequency analyses and geologic interpretations of crater formations. Impacts at shallow incidence, which are not uncommon, lead to ricochet of the impacting object accompanied with some entrained excavated materials at velocities only slightly reduced from the pre-impact value.
TL;DR: Product formulas constitute one of several bridges between numerical and functional analysis as discussed by the authors, and they represent algorithms intended to approximate some evolution equation and, in functional analysis, they are used to prove estimates, existence and representation theorems.
Abstract: Product formulas constitute one of several bridges between numerical and functional analysis. In numerical analysis, they represent algorithms intended to approximate some evolution equation and, in functional analysis, they are used to prove estimates, existence and representation theorems. Our aim is to survey the setting for product formulas and to discuss some recent results. Needless to say, we do not attempt to accommodate all the complex variations which occur in practical algorithms, nor the sharpest possible theoretical results. Nevertheless, we hope that our middle ground approach and some of the examples will be of interest to both groups. Because of its survey nature, we have not hesitated to include some well-known examples which are important for understanding the ideas. The general idea of product formulas is the following. Suppose one is interested in an initial value problem
TL;DR: In this paper, the collisional dynamics of a differentially rotating disk of particles are considered and the relation between the coefficient of restitution and the optical depth of identical, inelastic, smooth spheres is derived.
TL;DR: It is shown that the linkingNumber of a closed ribbon can be decomposed into the linking number of a reference ribbon plus a sum of locally determined "linking differences."
Abstract: A closed duplex DNA molecule relaxed and containing nucleosomes has a different linking number from the same molecule relaxed and without nucleosomes. What does this say about the structure of the nucleosome? A mathematical study of this question is made, representing the DNA molecule by a ribbon. It is shown that the linking number of a closed ribbon can be decomposed into the linking number of a reference ribbon plus a sum of locally determined "linking differences."
TL;DR: In this paper, the method of collocation using two finite element techniques is applied to the solution of the general population balance equation for particulate systems, and numerical solutions by both techniques are obtained in six cases for which analytical or asymptotic solutions are available.
TL;DR: In this paper, the effect of different forms of market organization on the efficiency, performance, convergence pattern and equilibrium level of prices has been investigated in the context of decentralized price adjustment processes.
Abstract: Economists have shown increasing interest in the analysis of information and organization
in decentralized price adjustment processes. This interest is most frequently manifested
at the theoretical level (summaries of the relevant literature, concepts, and methodologies
have been provided by Hurwicz [3] and Rothschild [4]), but it also has found expression
through several laboratory experimental studies. These latter have unusual appeal because
they can serve as a "proving ground" for the former. If well-formulated theories consistently
fail to predict simple laboratory behaviour, then one would be hesitant to trust
their predictions in richer environments. Furthermore, when replicable laboratory
behaviour can be demonstrated, one should seek those extensions of accepted theory which
explain why it occurs.
The laboratory studies have attempted to measure the effect of different forms of
market organization on the efficiency, performance, convergence pattern and equilibrium
level of prices. The variables of market organization examined have been the mechanisms
or rules under which prices are communicated and contracts are executed. The focus on
these particular variables has been motivated by the more prominent features of certain
observed exchange institutions rather than formal models based on pre-scientific, casual
observations of the kind that form the basis of embryonic modelling. We view the present
work as providing a rigorous empirical foundation for a more formal development of
theory.