Showing papers by "University of California, San Diego published in 1973"

Electrical Signs of Selective Attention in the Human Brain

Abstract: Auditory evoked potentials were recorded from the vertex of subjects who listened selectively to a series of tone pips in one ear and ignored concurrent tone pips in the other ear. The negative component of the evoked potential peaking at 80 to 110 milliseconds was substantially larger for the attended tones. This negative component indexed a stimulus set mode of selective attention toward the tone pips in one ear. A late positive component peaking at 250 to 400 milliseconds reflected the response set established to recognize infrequent, higher pitched tone pips in the attended series.

The Rapid Calculation of Potential Anomalies

Abstract: Summary It is shown how a series of Fourier transforms can be used to calculate the magnetic or gravitational anomaly caused by an uneven, non-uniform layer of material. Modern methods for finding Fourier transforms numerically are very fast and make this approach attractive in situations where large quantities of observations are available.

A technique for ultracryotomy of cell suspensions and tissues

Abstract: Ultracryotomy of fixed tissue has been investigated for a number of years but, so far, success has been limited for several reasons. The simple technique herein reported allows the ultracryotomy not only of a variety of tissues but also of single cells in suspension, with a preservation and visualization of ultrastructural detail at least equivalent to that obtained with conventional embedding procedures. In this technique, sucrose is infused into glutaraldehyde-fixed tissue pieces before freezing for the purpose of controlling the sectioning consistency. By choosing the proper combinations of sucrose concentration and sectioning temperature, a wide variety of tissues can be smoothly sectioned. Isolated cells, suspended in a sucrose solution, are sectioned by sectioning the frozen droplet of the suspension. A small liquid droplet of a saturated or near-saturated sucrose solution, suspended on the tip of an eyelash probe, is used to transfer frozen sections from the knife edge onto a grid substrate or a water surface. Upon melting of the sections on the surface of the sucrose droplet, they are spread flat and smooth due to surface tension. When the section of a suspension of single cells melts, individual sections of cells remain confined to the small area of the droplet surface. These devices make it possible to cut wide dry sections, and to avoid flotation on dimethyl sulfoxide solutions. With appropriate staining procedures, well-preserved ultrastructural detail can be observed. The technique is illustrated with a number of tissue preparations and with suspensions of erythrocytes and bacterial cells.

Study of the sensitivity of coupled reaction systems to uncertainties in rate coefficients. I Theory

Abstract: A method has been developed to investigate the sensitivity of the solutions of large sets of coupled nonlinear rate equations to uncertainties in the rate coefficients. This method is based on varying all the rate coefficients simultaneously through the introduction of a parameter in such a way that the output concentrations become periodic functions of this parameter at any given time t. The concentrations of the chemical species are then Fourier analyzed at time t. We show via an application of Weyl's ergodic theorem that a subset of the Fourier coefficients is related to 〈∂ci/∂kl〉, the rate of change of the concentration of species i with respect to the rate constant for reaction l averaged over the uncertainties of all the other rate coefficients. Thus a large Fourier coefficient corresponds to a large sensitivity, and a small Fourier coefficient corresponds to a small sensitivity. The amount of numerical integration required to calculate these Fourier coefficients is considerably less than that requi...

Theory of Metal Surfaces: Induced Surface Charge and Image Potential

Abstract: This paper contributes to the theory of the electron density distribution induced at a metal surface by a small static external charge distribution. As a first application, profiles of the charge induced by a uniform external electric field are obtained for metals of different bulk electron densities. A quantity of particular interest is the position of the center of mass, ${x}_{0}$, of these profiles, for which we present numerical values. (The $x$ axis is taken along the surface normal.) Next, the case of a small point charge $q$ with $x$ coordinate ${x}_{1}$ well outside the surface is treated. It is shown that the image potential experienced by such a charge has the form $\ensuremath{-}\frac{{q}^{2}}{[4({x}_{1}\ensuremath{-}{x}_{0})]}$, where ${x}_{0}$ is the above-mentioned quantity. We locate ${x}_{0}$, the effective position of the metal surface, relative to the last lattice plane of the crystal. We discuss the implications of these results for alkali adsorption on metal substrates, the capacitances of small-gap condensers, and field-emission experiments.

Plasma cell granulomas of the lung.

Abstract: Plasma cell granuloma of the lung, a designation that we consider preferable to “inflammatory pseudotumor,” represents localized proliferations predominantly of mature plasma cells, with Russell bodies, reticuloendothelial cells, and intermediate forms, supported by a stroma of granulation tissue. Other cellular elements, including lymphocytes and large mononuclear cells, may coexist with the plasma cells. The latter may have a large content of cytoplasmic fat, hence the term “xanthoma” or “fibroxanthoma” applied by some. The stroma may contain interlacing or whorled masses of fibroblasts, and may be focally ossified or calcified. It is often hyalinized with an appearance similar to that of paramyloid. These lesions are usually asymptomatic, and are most commonly detected in routine chest films as circumscribed “coin” lesions, or large masses. They may be static or increase slowly in size. In a minority, they are sessile or polypoid intrabronchial masses. More than two thirds of the patients are less than 30 years of age; indeed plasma cell granulomas are prominent among the large solitary intrapulmonary lesions in children. Bacterial cultures and skin tests for mycobacteria and fungi have been negative. The prognosis is good even after lobectomy, and probably even after segmental resection. Plasma cell granulomas have structural features and a natural history quite distinct from those of sclerosing hemangioma and myeloma.

The Immunopathology of Joint Inflammation in Rheumatoid Arthritis

Abstract: Publisher Summary This chapter focuses on the pathogenesis of rheumatoid arthritis. In an infectious etiology of rheumatoid arthritis, it is pertinent to consider the manner in which a pathogen might gain access to the synovial membrane. The joint seems to be uniquely predisposed to infection with some bacteria. Rheumatoid synovitis is characterized by a constellation of histological changes, which are characteristic but not pathognomonic of this disease. In hypertrophy of the synovial lining surface, the synovium appears edematous and inflamed and protrudes into the joint space as slender villous projections. In hyperplasia and hypertrophy of the synovial lining cells, the lining cells are multilayered, reaching to a depth of six to ten cells, as compared to the normal synovial lining that is only one to three cell layers. Vascular derangement—focal or segmental vascular changes—are a regular feature of rheumatoid synovitis. Cellular infiltrates—the connective tissue stronia of the synovial villus is packed with mononuclear cells—are collected into aggregates or follicles, particularly around small blood vessels, but true germinal centers are rarely seen.

Charged-Particle Scattering in the Presence of a Strong Electromagnetic Wave

Abstract: A simple and convenient approximation is obtained for the multiphoton energy-transfer processes which accompany the scattering of a charged particle by a scattering potential in the presence of a strong external electromagnetic field. It is expressed in terms of the differential elastic-scattering cross section combined with known functions, and is valid when the scattering potential is weak or when the wave frequency is small. A detailed form of the classical limit is obtained.

Thermal Model of Ocean Ridges

Abstract: MCKENZIE'S model of crustal creation at the ocean ridges1,2 and its derivatives3,4 predicts such features as the topography and high heat flow of the ridges. In spite of this success there are some unsatisfactory aspects of the model; for example, the arbitrary temperature distribution in the intrusive zone gives rise to infinite heat generation and the lithospheric thickness is a free parameter not determined by the physics. We offer here a simple refinement of McKenzie's model that overcomes these difficulties. The essential difference stems from the inclusion of terms in the boundary conditions to account for the evolution of latent heat in places where the plate is growing. We first describe the physical basis of the model.

Some approaches to best-match file searching

Abstract: The problem of searching the set of keys in a file to find a key which is closest to a given query key is discussed. After “closest,” in terms of a metric on the the key space, is suitably defined, three file structures are presented together with their corresponding search algorithms, which are intended to reduce the number of comparisons required to achieve the desired result. These methods are derived using certain inequalities satisfied by metrics and by graph-theoretic concepts. Some empirical results are presented which compare the efficiency of the methods.

Stimulation by cyclic adenosine monophosphate of plasmid deoxyribonucleic acid replication and catabolite repression of the plasmid deoxyribonucleic acid-protein relaxation complex.

Abstract: Colicinogenic factors ColE1 and ColE2 are bacterial plasmids that exist in Escherichia coli as supercoiled deoxyribonucleic acid (DNA) and as strand-specific, relaxation complexes of supercoiled DNA and protein. Newly replicated ColE1 DNA becomes complexed with protein after the replication event. This association of DNA and protein can take place under conditions in which DNA or protein synthesis is arrested. The addition of cyclic adenosine monophosphate (c-AMP) to normal cells growing in glucose medium results in a six- to tenfold stimulation in the rate of synthesis of the protein component(s) of the complex and a three- to fivefold stimulation in the rate of ColE1 DNA replication. Employing mutants deficient in catabolite gene activator protein or adenylate cyclase, it was shown that synthesis of both the plasmid-determined protein colicin E1 and the protein component(s) of the ColE1 relaxation complex is mediated through the c-AMP-catabolite gene activator protein system. Addition of c-AMP to ColE2-containing cells results in the stimulation of synthesis of ColE2 DNA and relaxation protein(s) as well as in the production of a protein component of the ColE2 relaxation complex that renders it sensitive to induced relaxation by heat treatment. In the case of ColE2, synthesis of the relaxation protein(s) is not dependent upon catabolite gene activator protein.

A study of plankton dynamics and nutrient cycling in the central gyre of the north pacific ocean1

Abstract: The dynamics of phytoplankton growth in relation to nutrient concentrations were studied in the subtropical central gyre of the North Pacific in November 1971. Rates of excretion of phosphate, ammonium, and urea-N by zooplankton and rates of assimilation of carbon, nitrate, ammonium, and urea-N by phytoplankton were measured. The growth rate of phytoplankton was estimated to be about 0.2-0.3 doublings day-’ in the 70-80-m mixed layer, apparently limited by concentrations of both nitrogen and phosphate. Only nitrogen concentration was so limiting at a station near the western edge of the California Current. No diel changes in concentrations of ambient nutrients were observed. Urea-nitrogen appears to be an important source of nitrogen for phytoplankton growth in these waters and to be an important excretory product of zooplankton. Concentrations of phosphate and ammonium were extremely low, but turnover times were estimated to bc of the order 3-5 days for ammonium and >lO days for urea and phosphate. Biomass of phytoplankton in the mixed layer was also very low, and corresponded approximately to that expected if a laboratory culture were operated as a nitrogenlimited chemostat with a concentration of about 0.48 pg-atom N liter-l in the incoming culture medium and a dilution rate of about 0.13 per day. Physiological differences were noted between the phytoplankton in the mixed layer and that living below the thermocline, as were differences in chemical composition (ratio of C:Chl a and C:N). The central gyre of the North Pacific Ocean is a trans-Pacific body of water extending approximately from 40”N to 15”N and maintained by the surrounding, anticyclonic pattern of surface circulation. Because of the gyre’s size, the effects of land masses and of waters of different origins are buffered in its center, which is therefore an appealing area in which to study plankton-nutrient relationships. As a result of generalized downwelling and mild winters, a thermocline appears to l Supported by U.S. Atomic Energy Commission Contract AT( 11-l )GEN 10, P.A. 20, National Science Foundation Grant No. GA-31167X, ind the Marine Life Research Program. Ship time supported by the National Science Foundation Alpha Helix program. Contribution from Scripps Institution of Oceanography. persist within the euphotic zone over a time measured at least in months, if not in years, and to isolate from deeper waters an environment. which is relatively stable in comparison with equatorial, temperate, and polar seas, or with coastal waters. Hence it is not far-fetched to think of stability in the mixed layer on a time scale rather long in comparison with the expected generation times of phytoplankton ( days) and zooplankton (weeks), notwithstanding seasonal fluctuations in the thickness of the mixed layer2 and in its temperature (Robinson and Bauer 1971). 2 In February 1973 we observed a mixed layer extending to 150 m throughout much of the central gyre, suggesting some mixture of deeper water into the surface layers. LIMNOLOGY AND OCEANOGRAPHY 534 JULY 1973, V. 18(4) NORTH PACWIC PLANKTON DYNAMICS 535 Although concentrations of plant nutrients and organisms are low (Reid 1962; Univ. California 1967, 1970; Sagi 1969; Marumo 1970)) absolute fluctuations in concentrations so far recorded are small in comparison to those in other areas. These variations appear to be of the order twofold to threefold about the mean both areally and seasonally, Sampling problems, for purposes of broad areal representation, would be eased if the apparent uniformity in concentrations of nutrients and organisms persists under careful measurement. The patchiness of diatom species has been compared quantitatively to that found in the subarctic North Pacific (Venrick 1972). All this information suggests that a steady state might pertain with respect to nutrient concentrations, plankton standing stocks, specific growth rates, and grazing. Such a situation would simplify the interpretation of measurements and permit the calculation or prediction of certain stocks and rates not readily measured with existing methods. Dugdale and Goering (1967) and Dugdale (1967) have provided a conceptual framework for the measurement and interpretation of nutrient-phytoplankton-zooplankton relationships in oligotrophic ocean waters with a persistent surface mixed layer. They conceive a two-layered water column: Specific growth rate of phytoplankton would be nutrient-limited in the mixed layer and light-limited below the thermocline. Grazing in the mixed layer would be closely coupled with phytoplankton production, with nitrogenous excretory products of the zooplankton the primary source of the growth rate-limiting nutrient for phytoplankton. Losses of nutrient to deep water, via sinking and migration of zooplankton, would be balanced by vertical turbulent diffusion of nitrate nitrogen from deep water, input of ammonium in rain ( cf. Menzel and Spaeth 1962) or by fixation of molecular nitrogen. This paradigm has many historical sources and seems consistent with present information, including the extensive studies of the Woods Hole group in the Sargasso Sea (Menzel and Ryther 1960, lQ61a,b; Steele and Menzel 1962) and the results of the EASTROPAC program in the eastern tropical Pacific Ocean (Thomas 1970a,b; Thomas and Owen 1971). Usually lacking in such studies have been measures of the degree of coupling between growth of phytoplankton and grazing by herbivores and between rates of excretion by zooplankton and rates of assimilation of nutrients by phytoplankton. Some estimates are available for coastal waters (Harris 1959; Martin 1968; Hargrave and Geen 1968). Pomeroy et al. (1963) presented an estimate for excretion relative to assimilation in the Gulf Stream as well as waters over the continental shelf. There has been no quantitative assessment of the rate of loss of nutrients to deep water, or their rcplaccment via upward diffusion or nitrogen fixation. The deeper water, in which growth of phytoplankton would be light-limited, usually shows a zone of chlorophyll concentrations higher than in the mixed layer above, and this zone may contribute an important fraction of the primary production to the water column (Anderson 1969, 1972; Hobson and Lorenzen 1972; Venrick et al. 1973). The elevated concentration of chlorophyll is due in part to a higher chlorophyll content of each phytoplankton cell ( cf. Steele 1964)) but in some cases the concentration of cells may also be elevated (Anderson 1972). Nitrate as a source of nitrogen for phytoplankton in this layer is relatively more important than in the mixed layer (Goering et al. 1970). We examined the rate of primary production of this deep chlorophyll layer and the physiological adaptations of phytoplankton to the very low light intensities and restricted spectral distribution of energy in hope of achieving a more adequate understanding of production processes in oligo-

Structural aspects of the fibrinogen to fibrin conversion.

Abstract: Publisher Summary The conversion of a soluble plasma protein, fibrinogen, into an insoluble polymeric gel termed “fibrin” is essential for the coagulation of vertebrate blood The complex series of events that precedes this conversion is primarily directed toward the production of thrombin from prothrombin by limited proteolysis The thrombin in turn catalyzes the release of a few small peptides from fibrinogen molecules, the resulting “fibrin monomers” polymerizing spontaneously to form the fibrin gel This chapter reviews the data gathered from a number of different fields involved in the study of the fibrinogen–fibrin conversion It focuses on the general shape of the native fibrinogen molecule and on the arrangement of the three pairs of nonidentical polypeptide chains that comprise the molecule and describes the relative locations of the amino and the carboxyterminals The best immediate hope for obtaining a real picture of fibrinogen lies with image reconstruction techniques and their application to the electron micrographs of ordered microcrystals It is possible that this approach will yield an outline of the native molecule and establish the general mode of the way the units are packed in fibrin

A system of nomenclature for band patterns of mouse chromosomes.

Abstract: Mouse chromosomes banded by quinacrine mustard staining, by the ASG technique, or by Giemsa staining following trypsinization or chymotrypsinization are described in detail. Three hundred and twelve regions within the mouse karyotype can be distinguished and a simple system of nomenclature is proposed for naming these regions. This nomenclature is applied to discussion of the locations of the breakpoints of twenty translocations and of many specific gene loci.

Tertiary Pacific Plate Motion Deduced from the Hawaiian-Emperor Chain

Abstract: Nearly all linear island and seamount chains on the Pacific plate are parallel to small circles generated about either a Hawaiian pole at 72° N., 83° W. or an Emperor pole at 17° N., 107° W. The rates of rotation of the Pacific plate relative to the Hawaiian melting (hot) spot are calculated from age data from the Hawaiian-Emperor chain. Extrapolation of the known age progression along the Hawaiian chain yields a 27-m.y. estimate of the age of the Hawaiian-Emperor bend; however, recent radiometric ages from Koko seamount in the southern Emperor chain indicate that the Hawaiian-Emperor bend is 42 to 44 m.y. old. The Pacific plate apparently moved slowly, if at all, relative to the Hawaiian melting spot from about 20 to 42–44 m.y. ago. The rates of rotation calculated are 1.3° per m.y. about the Hawaiian pole (0 to 20–25 m.y.), The proposed rotational motion of the Pacific plate relative to the Hawaiian melting spot can be used to predict ages of seamounts and islands in other chains if the various melting spots are fixed with respect to one another. Almost all ages from other chains are consistent with the rotational model except for two K-Ar ages from the Austral chain. The proposed rotational motion of the Pacific plate can be used to reconstruct a paleomagnetic polar path of the Pacific plate if the melting spots are fixed with respect to the spin axis. The melting-spot polar path agrees well with the Late Cretaceous and limited Neogene paleomagnetic data. However, an extension of this polar path through the Late Cretaceous based on the Line Islands appears to be inconsistent with existing paleomagnetic data. The assumption that melting spots are fixed relative to the spin axis (and therefore the equator) can be tested by comparing the equatorial belt of high sedimentation with the sediment distribution predicted by the rotational-plate motion model. Almost every Deep Sea Drilling Project (DSDP) site presently located just north of the equator has its highest sedimentation rate at the time when the melting-spot motion model predicts that it was located at the equator. An equatorial sedimentation model adapted after Winterer (1972) is combined with the melting-spot motion model to generate a predicted isopach map of the post-middle Eocene equatorial sediments. The resulting isopach map is remarkably similar to the Ewing and others (1968) map of actual isopachs determined by seismic profiling. No data at present require motion of the Hawaiian melting spot relative to the spin axis. The tectonic histories of Japan and the Aleutians appear to reflect the proposed discontinuities of Pacific plate motion.

Methods for measuring levels of well-being for a health status index.

Abstract: Three psychological scaling procedures—category rating, magnitude estimation, and equivalence—were used to measure the levels of well-being that student and health-leader judges in 14 experimental groups associate with 50 case descriptions of function status representing the continuum from complete well-being to death. No significant differences were detected for order of method presentation, interview situation, scaling method, student vs. leader judges, or most interactions among these factors. Category rating, the simplest and apparently the most reliable of the methods, was consistent with the results of the social choices implied in the equivalence technique. The results indicate the feasibility of measuring the social values of large numbers of cases in household interview surveys.

Fluorescence properties of natural phytoplankton populations

Abstract: The cellular fluorescence of chlorophyll a in natural phytoplankton was measured during vertical profiling in marine coastal waters. The ratio of in situ fluorescence to chlorophyll a concentration, which was considered as an index of cellular fluorescence, varied over a wide range, with large changes occurring both within the water column and between profiling sites. The variations were caused in part by an inhibition in the fluorescence of cells exposed to intense sunlight. The inhibition, which occurred at irradiances exceeding 0.15 langley (ly)/min, led to diel fluctuations in the fluorescence of those phytoplankton near the sea surface. The remaining variations were independent of changes in temperature, but were unexplained. Both light-dependent and light-independent variations in cellular fluorescence will affect the accuracy of the continuous, fluorometric measurement of in vivo chlorophyll.

Chromosome-sized DNA molecules from Drosophila

Abstract: Measurements of viscoelastic retardation times of detergent-Pronase lysates of Drosophila cells demonstrated the presence of large numbers of DNA molecules of a size commensurate with that of the chromosomes. The values estimated from the retardation times for the molecular weights of the largest molecules ranged from about 20×109 to 80×109 daltons depending on the species of Drosophila. The molecular weights of the DNA molecules were independent of the metaphase shapes (i.e., metacentric or submetacentric), but were proportional to the DNA contents of the chromosomes in the case of translocations or deletions. It was concluded, therefore, that the DNA molecules must run the length of the chromosome and cannot be discontinuous at the centromere. When compared with the values of the DNA contents of Drosophila chromosomes determined by other methods, the results were consistent with the model of one, or possibly two, DNA molecules per chromosome; the simplest conclusion, that there is only one DNA molecule per chromosome (for simple chromosomes), rests on a long extrapolation of an empirical relation between retardation time and molecular weight, but is also favored by indirect evidence. Further possibilities which could not be excluded were that the large DNA molecules contained Pronase-resistant, non-DNA links, or that a fraction of smaller DNA molecules might also have been present in the chromosomes. Chromosome-sized DNA molecules were obtained almost quantitatively from unsynchronized cultured cells, suggesting that the size of the chromosomal DNA is conserved throughout much of the cell cycle. The molecules were stable for periods of up to several days at 50° C in solutions containing detergent, Pronase, and EDTA.

Serum Androstenedione and Testosterone Levels During the Menstrual Cycle

Abstract: Utilizing specific radioimmunoassays serum androstenedione, testosterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH) were measured daily in the same aliquots of sera in 6 ovulatory menstrual cycles. In 3 of 6 cycles a progressive increase in serum androstenedione concentration was seen during the follicular phase. The mean androstenedione level during the middle third of the menstrual cycle was significantly higher than during the earlier (p < 0.01) or later (p < 0.001) portions. Serum testosterone levels in the same individual cycles showed random variations. Again the mean T level was significantly higher (p < 0.001) during the middle third as compared to either the beginning or end of the menstrual cycle.

Mechanism of demyelination in JHM virus encephalomyelitis. Electron microscopic studies.

Abstract: Weanling mice were given intraperitoneal inoculations of the neurotropic, JHM strain of mouse hepatitis virus, the virulence of which had been altered by repeated mouse passages. Five to seven days later many animals developed hind leg paralysis. The pathology consisted of an acute encephalomyelitis with patchy demyelinating lesions in the brain stem and spinal cord. Virus particles, consistent with the appearance of corona viruses, were found in the cytoplasm of cells that were identified as oligondendrocytes by demonstrating connections of their plasma membranes with myelin lamellae. Following the degeneration of oligodendrocytes the myelin sheaths disintegrated or were stripped off intact axons by cytoplasmic tongues of polymorpho- and mononuclear leucocytes that intruded between myelin lamellae. The findings indicate that JHM virus has an affinity for oligodendrocytes in weanling mice and that demyelination occurs subsequently to the degeneration of the infected oligodendrocytes.

Introduction to the renormalization group

Abstract: The basic idea of the renormalization group is introduced and illustrative examples are presented. Emphasis is put on the application to the theory of critical phenomena. This article is prepared for pedagogical purposes. It is written at a level that a second-year graduate student in physical sciences can understand. No previous knowledge of critical phenomena or field theory is needed. We make no attempt to survey the field or cover a wide range of subjects. On the contrary, we limit the scope to the most basic aspects. We choose to elaborate at length to make the basic idea clear and the definitions precise, and to go through the examples very carefully. We feel that once these basic aspect are understood, there will be no difficulty in confronting the rapidly expanding literature on this subject.