Showing papers by "California Institute of Technology published in 1977"

A general unified approach to modelling switching-converter power stages

Abstract: A method for modelling switching-converter power stages is developed, whose starting-point is the unified state-space representation of the switched notworks and whose end result is either a complete state-space description or its equivalent small-signal low-frequency linear circuit model. A new canonical circuit model is proposed, whose fixed topology contains all the essential input-output and control properties of any d.c.-to-d.c. switching converter, regardless of its detailed configuration, and by which different converters can be characterized in the form of a table conveniently stored in a computer data bank to provide a useful tool for computer-aided design and optimization. The new canonical circuit model predicts that, in general, switching action introduces both zeros and poles into the duty ratio to output transfer function in addition to those from the effective filter network.

Electromagnetic propagation in periodic stratified media. I. General theory

Abstract: The propagation of electromagnetic radiation in periodically stratified media is considered. Media of finite, semi-infinite, and infinite extent are treated. A diagonalization of the unit cell translation operator is used to obtain exact solutions for the Bloch waves, the dispersion relations, and the band structure of the medium. Some new phenomena with applications to integrated optics and laser technology are presented.

Software for C1 Surface Interpolation

Abstract: Publisher Summary This chapter discusses algorithm and underlying theory of software for C1 surface interpolation. There has been practically no theory to guide the development of algorithms for triangulation and there has been no practical static global criterion to characterize a preferred triangulation. An interpolation algorithm is interfaced with algorithms for contour plotting or surface perspective plotting. If the subroutines are available for doing contour or surface perspective plotting for data given on a rectangular grid, then the surface interpolation algorithm can be used to produce the values needed at the lattice points of a rectangular grid. The computerized representation of surfaces is a central issue in the field of computer-aided geometric design and plays an important role in the field of finite element methods. Some methods of building a triangular grid with a given set of nodes start by locating the boundary points of the convex hull of the point set. In some reasonable triangulation algorithms, the number of boundary points of the convex hulls of a sequence of sub­sets has an effect on the operation count.

Thermal and albedo mapping of Mars during the Viking primary mission

Abstract: The behavior of Mars as observed by the Viking infrared thermal mapper (IRTM) is considered. The IRTM is a 28-channel, 4-telescope radiometer that operated in six spectral bands. The studies considered include observations from the interplanetary phase through data collection on November 7, 1976. During this interval, thermal mapping of the whole Martian surface has been possible. Attention is given to polar temperatures, global albedos, predawn temperatures, a thermal inertia contour map, geometry considerations, clouds, aspects of predawn warming, and observations of earth.

The theory of information and coding

Abstract: 1. Entropy and mutual information 2. Discrete memoryless channels and their capacity-cost functions 3. Discrete memoryless sources and their rate-distortion functions 4. The Gaussian channel and source 5. The source-channel coding theorem 6. Survey of advanced topics for part I 7. Linear codes 8. BCH Goppa, and related codes 9. Convolutional codes 10. Variable-length source coding 11. Survey of advanced topics for part II.

Amplified reflection, phase conjugation, and oscillation in degenerate four-wave mixing

Abstract: A number of new optical effects that result from degenerate four-wave mixing in transparent optical media are proposed and analyzed. The applications are relevant to time-reversed (phase-conjugated) propagation as well as to a new mode of parametric oscillation.

Long-lasting morphological changes in dendritic spines of dentate granular cells following stimulation of the entorhinal area.

Abstract: Stimulation of the perforant path induces a long-lasting increase in the area of dendritic spines, which are sites of termination of the stimulated pathway in the distal third of the dentate molecular layer No enlarged spines were found in the proximal third of the dentate molecular layer, where the commissural afferents terminate Following a single tetanic stimulus of 30 sec duration at 30/sec, spines became significantly larger by 15%, 38%, 35% and 23% within poststimulation intervals of 2–6 min, 10–60 min, 4–8 h, and 23 h, respectively Axon terminals decreased their area by 15% within the 2–6 min interval and the vesicle density was decreased by 19% within the 10–60 min interval Both changes were reversible and terminals resumed their prestimulation condition at longer intervals (>4 h) The initial enlargement of spines was interpreted as being due to a glutamate-induced increase in the sodium permeability of the spine membrane, whereas for the long-lasting enlargement an increase in protein synthesis was postulated The long-lasting enlargement of dendritic spines in the dentate molecular layer following a short train of stimuli delivered to the perforant path, supports the postulate which links such a change to the mechanism of long-lasting postactivation potentiation observed in this pathway

A general unified approach to modelling switching DC-tO-DC converters in discontinuous conduction mode

Abstract: A method for modelling switching converters in the discontinuous conucction mode is developed, whose starting point is the unified state-space representation, and whose end results is a complete linear circuit model which correctly represents all essential features, namly, the input, output, and transfer properties (static dc as well as dynamic ac small signal). While the method is generally applicable to any switching converter operating in the discontinuous conduction mode, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The outlined method lends itself easily to investigation of the discontinuous conduction mode in more complex structures (cascade connection of buck and boost converters, for example), in which more thean one inductor current may become discontinuous. As opposed to other modelling techniques, the new method considers the discontinuous conduction mode as a special case of the continuous conduction mode.

Two types of magnetospheric ELF chorus and their substorm dependences

Abstract: The distribution of extremely low frequency (10-1500 Hz) magnetospheric chorus to all local times and latitudes is investigated in order to determine dependence on substorms, and to evaluate the conditions under which chorus is generated. The analysis carefully separates space and time effects by an investigation of data obtained by the OGO 5 search coil magnetometer. A study of spatial dependencies shows that chorus occurs in two magnetic regions: equatorial chorus is located near the equator, and high-latitude chorus is located above 15 degrees. An analysis of chorus in each of the regions illustrates that equatorial chorus is definitely related to substorm, whereas high-latitude chorus often occurs within magnetically quiet intervals.

Well-posed quasi-linear second-order hyperbolic systems with applications to nonlinear elastodynamics and general relativity

Abstract: Existence, uniqueness and well-posedness for a general class of quasi-linear evolution equations on a short time interval are established. These results, generalizing those of [29], are applied to second-order quasi-linear hyperbolic systems on IR" whose solutions (u(t),il(t)) lie in the Sobolev space H^(s+1) x H^5. Our results improve existing theorems by lowering the required value of s to s > (n/2) + 1, or s > n/2 in case the coefficients of the highest order terms do not involve derivatives of the unknown, and by establishing continuous dependence on the initial data for these values. As consequences we obtain well-posedness of the equations of elastodynamics if s>2.5 and of general relativity if s>l.5; s>3 was the best known previous value for systems of the type occuring in general relativity ([12], [16], [23]).

Non-Standard Analysis

Abstract: 1. As early as 1934 it was pointed out by Thoralf Skolem (see [17]) that there exist proper extensions of the natural number system which have, in some sense, ‘the same properties’ as the natural numbers. The title of Skolem’s paper indicates that the purpose of it was to show that no axiomatic system specified in a formal language, in Skolem’s case the lower predicate calculus, can characterize the natural numbers categorically. At that time, however, Skolem did not concern himself with the properties of the structures whose existence he had established. In due course these structures became known as non-standard models of arithmetic. For nearly thirty years since the appearance of Skolem’s paper non-standard models were not used or considered in any sense by the working mathematician. Robinson’s fundamental paper, which appeared in 1961 under the title ‘Non-standard Analysis’, (see [11]) changed this situation dramatically. In this paper Abraham Robinson was the first to point out that this highly abstract part of model theory could be applied fruitfully to a theory so far removed from it as the infinitesimal calculus. As a result Robinson obtained a firm foundation for the non-archimedian approach to the calculus based on a number system containing infinitely small and infinitely large numbers, in a manner almost identical to that suggested by Leibniz some three centuries ago, and which predominated the calculus until the middle of the nineteenth century when it was rejected as unsound and replaced by the ϵ, δ-method of Weierstrass.

Periodic structures for integrated optics

Abstract: This paper deals with the theory and device applications of periodic thin-film waveguides. Topics treated include mode solutions, optical filters, distributed feedback lasers (DFB), distributed Bragg reflector (DBR) lasers, grating couplers, and phase matching in nonlinear interactions.

Aluminum-26 in the early solar system - Fossil or fuel

Abstract: The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of Mg-26 of up to 10% were found. These excesses correlate strictly with the Al-27/Mg-24 ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of Al-26 within the solar system and of mixing of interstellar dust grains containing fossil Al-26 with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of Al-26 in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred Al-26/Al-27 would melt within about 300,000 years.

Oxygen and Hydrogen Isotopic Ratios in Plant Cellulose

Abstract: The variations of the D/H and (18)O/(16)O ratios of nonexchangeable hydrogen and oxygen in plant cellulose reveal systematic differences between terrestrial plant groups. The slope of deltaD versus delta(18)O of cellulose from a variety of aquatic plants is close to 8 (the meteoric water value), while the slope for a number of terrestrial species is greater than or equal to about 24. Two models involving incorporation of CO(2) and H(2)O into cellulose precursors are proposed to account for these differences. Effects of evaporative transpiration on the isotopic composition of water in leaves are measured and discussed in the context of these models.

Solar seismology. II - The stochastic excitation of the solar p-modes by turbulent convection

Abstract: We test the hypothesis that the solar p-modes are stabilized by damping due to turbulent viscosity in the convective zone. Starting from the assumption that the modes are stable, we calculate expectation values for the modal energies. We find that the interaction between a p-mode and the turbulent convection is such that the modal energy tends toward equipartition with the kinetic energy of turbulent eddies whose lifetimes are comparable to the modal period. From the calculated values of the modal energies, we compute rms surface velocity amplitudes. Our predicted rms surface velocities range from 0.01 cm/sec for the fundamental radial mode to 0.6 cm/sec for the radial mode whose period is approximately 5 minutes. The predicted surface velocities for the low order p-modes are much smaller than the velocities inferred from recent observations.

On the Decline of Competition in Congressional Elections

Abstract: Several authors have observed a decline in the number of competitive congressional districts during the past two decades. Various explanations have been proposed for this change. Among these are theories attributing major causal significance to changing methods of drawing district boundaries, and increasing control of campaign resources by incumbents. These theories are examined critically and arguments are advanced for their rejection. The principal cause of the decline of competition for congressional seats appears to rest on a change in individual voting behavior.

Properties of aerosols in the Martian atmosphere, as inferred from Viking lander imaging data

Abstract: Observations of the Martian sky, Phobos, and the sun were taken with the Viking lander imaging cameras to obtain information on the properties of the atmospheric aerosols. Atmospheric optical depths were derived from the observations of the brightness of the celestial objects. Information on the absorption coefficient, mean size, and shape of the aerosols was derived from studies of the sky brightness. For this purpose we used a multiple-scattering computer code that employed a recently developed technique for treating scattering by nonspherical particles. By monitoring the brightness of the twilight sky we obtained information on the vertical distribution of the particles. Three types of aerosols are inferred to have been present over the landers during the summer and fall season in their hemisphere. A ground fog made of water ice particles was present throughout this period. It formed late at night during the summer season and dissipated during the morning. We infer that during the summer the frost point temperature was 195°K and the water vapor volume mixing ratio equaled about 1× 0−4 near the ground at VL-2. Assuming that condensation occurs only on suspended soil particles, we estimate that the average particle radius of the fog was about 2 μm and that the fog's depth equaled approximately 0.4 km. A higher-level ice cloud was prominent only during the fall season, when it was a sporadic source of atmospheric opacity at VL-2. The formation of upper level water ice clouds during the summer may have been inhibited by dust heating of the atmosphere. Suspended soil particles were present throughout the period of observation. During the summer they constituted the only major source of opacity in the afternoon and most of the night. The cross-section weighted mean radius of these aerosols is about 0.4 μm. They have a nonspherical but equidimensional shape and rough surfaces. These soil particles have a scale height of about 10 km, which is comparable to the gas scale height, and they extend to an altitude of at least 30 km. The principal opaque mineral in these particles is magnetite, which constitutes 10%±5% by volume of this material. We propose that soil particles, as well as any associated water ice, are eliminated from the atmosphere, in part, by their acting as condensation sites for the growth of CO2 ice particles in the winter polar regions. The resultant CO2-H2O-dust particle is much larger and therefore has a much higher fallout velocity than an uncoated dust or water ice particle.

Particle emission rates from a black hole. III. Charged leptons from a nonrotating hole

Abstract: The Hawking emission rates from a nonrotating black hole of small charge are calculated for electrons and muons and their antiparticles. During the stochastic emission of these charged leptons, the charge of the hole fluctuates. Assuming that the only type of charged particle emitted significantly by a hole of mass $M$ is one of these spin-1/2 species with mass $\ensuremath{\mu}$ and charge $e$, the probability distribution for the charge of the hole is computed for $0 \ensuremath{\le} \frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c} \ensuremath{\le} 0.4$. The rms value varies from $6.14e$ for $\frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c} = 0$ to $2.76e$ for $\frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c}=0.4$ and is predicted to be $2.34e$ for $\frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c}gg1$. The electrostatic attraction between the emitted particle and its antiparticle, along with the charge fluctuations, causes the average emission rate and power to be lower than for otherwise-similar uncharged particles. This effect of the charge is calculated (ignoring radiative and self-energy corrections, which are of the same order in $e$) to be a few percent, depending upon $\frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c}$. The particle rest mass $\ensuremath{\mu}$ also impedes the emission, but by factors which can become much greater for a large enough hole: The average power is reduced to 50% of its value for massless spin-1/2 particles at $\frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c} = 0.160$ ($M = 8.33\ifmmode\times\else\texttimes\fi{}{10}^{16}$ g for electrons, 4.03 \ifmmode\times\else\texttimes\fi{} ${10}^{14}$ g for muons) and to 10% at $\frac{\mathrm{GM}\ensuremath{\mu}}{\ensuremath{\hbar}c} = 0.271$ ($M = 1.41\ifmmode\times\else\texttimes\fi{}{10}^{17}$ g for electrons, 6.82 \ifmmode\times\else\texttimes\fi{} ${10}^{14}$ g for muons). It is estimated that muons and heavier particles would contribute about 14% of the power of a nonrotating black hole of $M = 5\ifmmode\times\else\texttimes\fi{}{10}^{14}$ g, helping it to decay away in nearly 16 \ifmmode\times\else\texttimes\fi{} ${10}^{9}$ yr, roughly the present age of the universe.

Application of magnetic microspheres in labelling and separation of cells

Abstract: POLYMERIC microspheres conjugated to antibodies and lectins have been used previously as cell surface markers for the detection and localisation of antigens and lectin receptors using scanning electron microscopy (SEM) (refs 1–4). In this report we describe a new, more versatile cell surface probe consisting of iron-containing polymeric microspheres tagged with fluorescent dyes and chemically coupled to antibodies or lectins. The magnetic and fluorescent properties of these microspheres have been utilised in the magnetic separation of red blood cells (RBC) and lymphoid cells and in the detection of immunoglobulin (Ig) receptors and wheat germ agglutinin (WGA) receptors on lymphocytes and Hela cells by SEM and fluorescent microscopy.

Desert Varnish: The Importance of Clay Minerals

Abstract: Desert varnish has been characterized by infrared spectroscopy, x-ray diffraction, and electron microscopy. It is a distinct morphological entity having an abrupt boundary with the underlying rock. Clay minerals comprise more than 70 percent of the varnish. Iron and manganese oxides constitute the bulk of the remainder and are dispersed throughout the clay layer.

Seismic structure of the Transverse Ranges, California

Abstract: Travel-time data obtained from both natural and artificial events occurring in southern California indicate a major, lateral crustal transition within the Transverse Range Province The eastern crust is very similar to the adjacent Mojave region, where a crustal velocity of 62 km/sec is typically observed The western ranges are dominated by an extensive 67 km/sec layer P_n velocity beneath the western Mojave, Transverse Ranges, and northern Peninsular Ranges is 78 km/sec The crustal thickness of these provinces is 30 to 35 km The Transverse Ranges do not have a distinct crustal root Unlike other provinces within southern California, the Transverse Ranges are underlain at a depth of 40 km by a refractor with a P-velocity of 83 km/sec P-delays from a vertically incident, well-recorded teleseism suggest that this velocity anomaly extends to a depth of 100 km These data indicate that this high-velocity, ridge-like structure is coincident with much of the areal extent of the geomorphic Transverse Ranges and is not offset by the San Andreas fault Four hypotheses are advanced to explain the continuity of this feature across the plate boundary: (1) dynamic phase change; (2) a coincidental alignment of crust or mantle anomalies; (3) the litho-sphere is restricted to the crust; (4) the plate boundary at depth is displaced from the San Andreas fault at the surface Within the context of the last model, we suggest the plate boundary at depth is at the eastern end of the velocity anomaly, in the vicinity of the active Helendale-Lenwood-Camprock faults The regionally observed 78 km/sec layer is suggested as a zone of decoupling necessary to accommodate the horizontal shear that must result from the divergence of the crust and upper mantle plate boundaries The geomorphic Transverse Ranges are viewed as crustal buckling caused by the enhanced coupling between the crust and upper mantle which is suggested by the locally thin, 78 km/sec layer

Electromagnetic propagation in periodic stratified media. II. Birefringence, phase matching, and x-ray lasers *

Abstract: The theory of electromagnetic Bloch waves in periodic stratified media is applied to the problems of birefringence and group velocity in these media. The relevance of periodic media to phase matching in nonlinear mixing experiments and to laser action in the x-ray region is discussed.

Infrared Astronomical Satellite

Abstract: The objective of the Infrared Astronomical Satellite is to produce an unbiased all-sky survey in the wavelength region between 8 and 120 microns. Using a 60 cm diameter helium cooled telescope and detector arrays which are essentially zodiacal light background photon noise limited, heretofore unprecedented sensitivity can be achieved. The optical design, the focal plane layout and expected performance of the current design concept are discussed.

The finite anti-plane shear field near the tip of a crack for a class of incompressible elastic solids

Abstract: The present paper is concerned with an infinite slab containing a crack and deformed at infinity to a state of finite simple shear. The material of the slab is taken to be homogeneous, isotropic, elastic, and incompressible, and is further assumed to belong to a class of materials which admit nontrivial states of anti-plane shear. The analysis is carried out for the fully nonlinear equilibrium theory of finite elasticity. The stress field near the crack-tips is studied in detail; one of the special materials considered is such that the shear stresses near a crack tip remain bounded, despite the presence of unbounded displacement gradients. An analogy between the crack problem in finite anti-plane shear and the problem of transonic flow of a gas past a flat plate is pointed out and discussed.

Two Mutations of Synaptic Transmission in Drosophila

Abstract: Evoked transmitter release is abnormal at the larval neuromuscular junctions of two Drosophila mutants. Following a single nerve impulse, the increased calcium conductance at the nerve terminal, which lasts for 1 ms in normal larvae, lasts for at least 60 ms in one mutant and several seconds in the other. Both mutations appear to affect the same gene on the X-chromosome. Normal larvae treated with 4-aminopyridine, a potassium channel blocking agent, mimic the abnormal synaptic transmission of one mutant. Normal larvae treated with tetraethylammonium, another potassium channel blocking agent, mimic the abnormal synaptic transmission of the other mutant. From these and other experiments, we suggest that the abnormal neuromuscular transmission in these mutants may be caused by defective potassium channels in the nerve terminal membrane.