Showing papers by "University of Illinois at Urbana–Champaign published in 1979"

An introduction to lattice gauge theory and spin systems

Abstract: This article is an interdisciplinary review of lattice gauge theory and spin systems. It discusses the fundamentals, both physics and formalism, of these related subjects. Spin systems are models of magnetism and phase transitions. Lattice gauge theories are cutoff formulations of gauge theories of strongly interacting particles. Statistical mechanics and field theory are closely related subjects, and the connections between them are developed here by using the transfer matrix. Phase diagrams and critical points of continuous transitions are stressed as the keys to understanding the character and continuum limits of lattice theories. Concepts such as duality, kink condensation, and the existence of a local, relativistic field theory at a critical point of a lattice theory are illustrated in a thorough discussion of the two-dimensional Ising model. Theories with exact local (gauge) symmetries are introduced following Wegner's Ising lattice gauge theory. Its gauge-invariant "loop" correlation function is discussed in detail. Three---dimensional Ising gauge theory is studied thoroughly. The renormalization group of the two dimensional planar model is presented as an illustration of a phase transition driven by the condensation of topological excitations. Parallels are drawn to Abelian lattice gauge theory in four dimensions. Non-Abelian gauge theories are introduced and the possibility of quark confinement is discussed. Asymptotic freedom of O(n) Heisenberg spin systems in two dimensions is verified for $n\ensuremath{\ge}$ and is explained in simple terms. The direction of present-day research is briefly reviewed.

Temperature-dependent X-ray diffraction as a probe of protein structural dynamics

Abstract: X-ray diffraction at four temperatures from 220 to 300 K coupled with crystallographic refinement yields the mean-square displacements and conformational potentials of all 1,261 non-hydrogen atoms of metmyoglobin. The results are interpreted to indicate a condensed core around the haem, semi-liquid regions towards the outside and a possible pathway for ligands. It is concluded that X-ray diffraction can provide the spatial distribution of the dynamic features of a protein.

Dependent Development: The Alliance of Multinational, State, and Local Capital in Brazil

Abstract: In order to analyze Brazil's recent accumulation of capital in the light of its continued dependence, Peter Evans focuses on the relationships among multinational corporations, local private entrepreneurs, and state-owned enterprises that have developed in Brazil over the last decade. He argues that while relations among the three kinds of capital continue to be contradictory, a triple alliance has been formed that provides the social structural basis for the pattern of local industrialization that has emerged. The author begins with a review of the theories of imperialism and dependency in the third world. Placing the Brazilian experience of the last twenty years in its historical context, he traces the country's evolution from the period of "classic dependence" at the turn of the century to the current stage of "dependent development." In conclusion, Professor Evans discusses the implications of the Brazilian model for other third world countries. Examining the nature of the triple alliance as it is manifested in such industries as pharmaceuticals, textiles, and petrochemicals, the author reveals the complex differentiation of the groups' roles in industrialization and lays bare the grounds for their collaboration and their conflict. He consequently shows how the differing interests, power, and capabilities of the three groups have combined to produce a system promoting industrialization that benefits the elite partnership but excludes the larger population from the rewards of growth.

Brassinolide, a plant growth-promoting steroid isolated from Brassica napus pollen

Abstract: Extracts of Brassica napus L. (rape) pollen (family, Cruciferae) have been reported to produce a novel growth-promoting effect when applied to young pinto bean plants1,2. Fractions that are active in the bean second-internode assay3 give rise to both increased cell elongation and cell division4. The validity of these early reports has been questioned because biological activity was not correlated with any one pure compound5. Subsequently, we showed that isolation of the growth promoter was complicated by the presence of chromatographically similar, inactive components that were identified as 6-D-glucopyranosyl esters of long-chain fatty acids6. We now report the isolation, structure determination and biological activity of this new plant growth promoter, named (22R, 23R, 24S)-2α-3α,22,23-tetrahydroxy-24-methyl-6,7-s-5α-cholestano-6,7-lactone or brassinolide (Fig. 1).

Theory and experiment on microstrip antennas

Abstract: A simple theory based on the cavity model is developed to analyze microstrip antennas. Formulas for numerous canonical shapes are given. In general the theoretically predicted radiation patterns and impedance loci closely agree with those measured for many antennas of various shapes and dimensions investigated thus far. In fact, this theory enables the computation of both patterns and impedance loci with little effort. The input admittance locus generally follows a circle of nearly constant conductance, but its center is shifted to the inductive region in the Smith chart plot. Peculiar properties for the case with degenerate or slightly degenerate eigenvalues are discussed. An accurate formula for determining the resonant frequency of a rectangular microstrip antenna is also given.

Information processing in visual search: a continuous flow conception and experimental results.

Abstract: This paper reexamines the visual search process, and visual information processing more generally, from a perspective of the continuous flow of information and responses through the visual system. The results from three experiments are reported which support the continuous flow conception: Information accumulates gradually in the visual system, with concurrent priming of responses. The first two experiments investigated the processing of display stimuli which varied in size and figure-ground contrast in a nonsearch task, and provided evidence confirming a continuous flow model. Experiment 3 employed an asynchronous onset of target and noise and provided convergent evidence of the accumulative nature of information and response priming in visual processing.

Estimation of Nutrient Requirements from Growth Data

Abstract: Two least squares methods of estimating nutrient requirements from growth data were compared One method involved fitting a broken line by the method of least squares The requirement was taken as the abscissa of the breakpoint in the curve The other method involved fitting an appropriate exponential function to the growth data and estimating the requirement as the abscissa of the point on the fitted curve whose ordinate was 95% of the upper asymptote For the nine sets of data studied, the broken line provided adequate fits for only six The nonlinear models provided adequate fits for all the data studied When both the broken line and the chosen nonlinear model provided adequate fits, the estimated requirements were nearly the same However, the consistently good fits obtained with the nonlinear models suggest that this approach may generally be more useful

Accretion by rotating magnetic neutron stars. II. Radial and vertical structure of the transition zone in disk accretion.

Abstract: The radial and vertical structure of the transition zone at the magnetospheric boundary of an aligned rotating neutron star accreting matter from a Keplerian disk are calculated. The results obtained indicate that: (1) the inner edge of the disk is located where the integrated magnetic stress acting on the disk plasma becomes comparable to the integrated material stress associated with its inward radial drift and orbital motion; (2) the stellar magnetic field threads the disk near its inner edge via the Kelvin-Helmholtz instability, turbulent diffusion, and reconnection, producing a broad transition zone between the unperturbed disk flow and corotating magnetosphere; (3) the transition zone consists of two qualitatively different regions, viz., a broad outer transition zone where the motion is Keplerian and a narrow inner zone, or boundary layer, where the departure from Keplerian motion is substantial; (4) the stellar magnetic field is largely but not entirely screened by currents flowing in the boundary layer; and (5) there are no steady-flow solutions for sufficiently fast stellar rotation.

An improved theory for microstrip antennas and applications

Abstract: An improvement to a recently reported theory for the analysis of the pattern and impedance loci of microstrip antennas is developed. It yields a theory which is simple and inexpensive to apply. The fields in the interior of the antennas are characterized in terms of a discrete set of modes. The poles corresponding to these modes are complex and depend on the losses in the antenna. The representation of the fields in terms of these modes is rigorous only for a bona fide cavity with no copper loss. The proper shift in the complex poles due to the addition of copper and radiative losses is approximated by lumping the latter two together with the dielectric loss to form an effective loss tangent. By so doing, it is found that the resulting expressions for impedance of the microstrip antenna are in good agreement with measured results for all modes and feed locations. The theory is applied to the evaluation of impedance variation with feed location, to multiport analysis, and to the design of circularly polarized microstrip antennas.

Beyond Literal Similarity

Abstract: Hitherto, theories of similarity have restricted themselves to judgments of what might be called literal similarity. A central thesis of this article is that a complete account of similarity needs also to be sensitive to nonliteralness, or metaphoricity, an aspect of similarity statements that is most evident in similes but that actually underlies metaphorical language in general. Theoretical arguments are advanced in support of the claim that metaphoricity can be represented in terms of the relative degrees of salience of matching (or matchable) attributes of the two terms in a comparison. A modification of Tversky's account of similarity is proposed. The implications of this proposal for similarity statements are discussed, along with implications for the psychological processes involved in their comprehension. It is argued that the general account of similarity proposed, including, as it does, nonliteral similarity, can form not only the basis of a theory of metaphor but can also give a credible account of the relationship between metaphor, analogy, and similarity.

Magnetite in Freshwater Magnetotactic Bacteria

Abstract: A previously undescribed magnetotactic spirillum isolated from a freshwater swamp was mass cultured in the magnetic as well as the nonmagnetic state in chemically defined culture media. Results of Mossbauer spectroscopic analysis applied to whole cells identifies magnetite as a constituent of these magnetic bacteria.

Oilseed phytates: Nutritional implications

Abstract: The protein quantity and quality, caloric value, and overall nutrient content of oilseeds are quite good. However, oilseeds are high in phytic acid and contain fiber and perhaps other binding agents which reduce mineral bioavailability from the seeds. Phytic acid, the hexaphosphate of myoinositol, functions as the chief storage form of phosphate and inositol in mature seeds. On a dry basis, whole oilseeds contain about 1.5% while some oilseed protein concentrates can contain over 7.0% of the compound. Phytic acid is a strong chelating agent that can bind mono- and divalent metal ions to form the complex phytate. Published results from numerous animal feeding trials suggest poor bioavailability of minerals such as zinc, calcium, magnesium, phosphorus and possibly iron from diets containing high phytate foods. Recent studies involving the feeding of soy products to rats suggest that zinc is the mineral of most concern as its bioavailability from some soy products is quite low. Prediction of mineral bioavailability from phytate-containing foods is complicated by the complex interactions between the minerals and phytic acid contained in the foods, intestinal and the meal phytase activities, previous food processing conditions (especially pH), digestibility of the foods as well as the physiological status of the consumer of the foods. Very little is known about the chemistry of such interactions. Therefore, most of the emphasis in controlling or reducing mineral binding in oilseed products has been placed upon development of methodology for phytate removal.

Anaerobic bacterium that degrades fatty acids in syntrophic association with methanogens

Abstract: A new species of anaerobic bacterium that degrades the even-numbered carbon fatty acids, butyrate, caproate and caprylate, to acetate and H2 and the odd-numbered carbon fatty acids, valerate and heptanoate, to acetate, propionate and H2 was obtained in coculture with either an H2-utilizing methanogen or H2-utilizing desulfovibrio. The organism could be grown only in syntrophic association with the H2-utilizer and no other energy sources or combination of electron donor and acceptors were utilized. It was a Gram-negative helical rod with 2 to 8 flagella, about 20 nm in diameter, inserted in a linear fashion about 130 nm or more apart along the concave side of the cell. It grew with a generation time of 84 h in co-culture with Methanospirillum hungatii and was present in numbers of at least 4.5×10-6 per g of anaerobic digestor sludge.

Orderings for term-rewriting systems

Abstract: Methods of proving that a term-rewriting system terminates are presented. They are based on the notion of "simplification orderings", orderings in which any term that is homeomorphically embeddable in another is smaller than the other. A particularly useful class of simplification orderings, the "recursive path orderings", is defined. Several examples of the use of such orderings in termination proofs are given.

The Effect of Background Knowledge on Young Children's Comprehension of Explicit and Implicit Information:

Abstract: To investigate the applicability of schema-theoretic notions to young children's comprehension of textually explicit and inferrable information, slightly above-average second grade readers with str...

Influence of quenched impurities on first-order phase transitions

Abstract: Microscopic random quenched impurities may or may not produce rounding of a first-order phase transition. We derive a criterion for the appearance of rounding due to local fluctuations in thermodynamic phase. Such fluctuations occur when the free-energy lowering due to taking advantage of local fluctuations in impurity density more than offsets the free-energy cost of the interface produced. The argument also predicts the spatial scale of such phase fluctuations, when they occur. In some situations this scale is just the coherence length $\ensuremath{\xi}$; in others, the inhomogeneity develops over "domains," which may be much larger than $\ensuremath{\xi}$. Near a second-order transition our criterion reduces to the one due to Harris. We specifically discuss what happens when a first-order transition becomes second order as an external parameter is varied.

Contribution to reproductive effort by photosynthesis of flowers and fruits

Abstract: REPRODUCTION is often a lethal or semi-lethal activity, and for iteroparous plants it is often possible to show that reproduction has costs that are expressed in a reduced growth rate and/or an increased death rate1. Attempts have been made to compare life history patterns in flowering plants by measuring the fraction of a plant's annual dry matter production (or calorific value) that is allocated to reproduction (for example refs 2–4). The assumption is that the reproductive parts represent a cost in energy or materials. Clearly mineral nutrients and water must be gained by the reproductive structures from the remainder of the plant, but this is not necessarily true for the energetic and carbon economy of the reproductive structures. Many flowers and fruits are green and a fraction of the energy and carbon might be obtained by direct photosynthesis within these structures. This might be especially important during embryo growth if carpels and other organs that remain attached after flowering are green. In such cases the conventional estimation of reproductive effort (dividing seed weight by plant weight) would be incorrect and comparison of life history patterns and their evolutionary meaning would be invalid. There are reports of significant contributions of in situ photosynthesis in flower and seeds to their growth. Biscoe et al. have estimated that 47% of the carbon required for seed production in barley is provided by photosynthesis of reproductive and immediately adjacent plant structures5. Bazzaz and Carlson have shown that in the annual weed Ambrosia trifida L., net photosynthesis by reproductive structures amounts to 41 and 51%, respectively, of the carbon required for male and female inflorescences6. Here we report an analysis of the carbon budget of reproduction for 15 temperate deciduous trees. The budget was determined by measuring the weight, photosynthesis and dark respiration of flowers or inflorescences from bud break until seed maturity.

Event-related Brain Potentials: A Tool in the Study of Human Information Processing

Abstract: A cognitive psychologist of note who is not particularly impressed with event-related potentials (ERPs) commented recently, while reviewing a grant application, that studies of the behavioral correlates of ERPs can be described as studies in which “phenomena are in search of a theory.” The intent was pejorative, but I found the statement complimentary. I was especially pleased because several years ago in a review of one of my own proposals another referee suggested that in the field of ERPs “one sees a technique futilely searching for phenomena!” We have, it would seem, made good progress in the last decade if we have found phenomena and are now searching for a theory. A detailed review of this progress is presented by Callaway, Tueting, and Koslow (in press).

Is visual information integrated across successive fixations in reading

Abstract: College students read a passage presented in AlTeRnAtInG cAsE on a CRT while their eye movements were monitored. During certain saccades, the case of every letter was changed (a became A, B became b). This change was not perceived and had no effect on eye movements. Apparently visual features of the type which specify the difference between upper- and lowercase letters are not integrated across fixations during reading.

Predation, competition, and zooplankton community structure: An experimental study1,2

Abstract: An experimental investigation of the zooplankton community of a small Minnesota pond was conducted for 2 years to determine the mechanisms maintaining its structure and to show that it is predictably organized. A mechanistic interpretation of the structure of this community cannot be made solely on the basis of predation, but also requires evaluation of the relative competitive abilities of the herbivores. The presence of Chaoborus and fish place predictable constraints on the abundance of zooplankton species in this pond. The competitive dominant (Cerioduphniu reticulata) is of intermediate size and is removed when either predator is abundant. In the presence of intense Chaoborus predation, Cerioduphniu is replaced by a larger subordinate competitor, Daphnia pulex; when fish predation is intense, smaller species (Rosminu Zongirostris and rotifers) increase. These small species are also able to maintain large populations in vertebrate-free environments when Chaoborus is rare. When these small herbivores are abundant, two additional invertebrate predators (Cyclops vernalis and Asplunchnu priodontu) arrive, neither of which seems able to reduce its prey to extinction. Recent studies provide ample evidence that predator-prey interactions are of major significance in structuring freshwater zooplankton communities (see Hall et al. 1976). Vertebrate planktivores (fish and salamanders) feed visually and remove the largest and most conspicuous zooplankton (Brooks 1968; Werner and Hall 1974; Zaret and Kerfoot 1975; O’Brien et al. 1976); invertebrate predators (predaceous copepods and rotifers, midge larvae, and Leptodora) cannot handle the large herbivores but prey extensively on small species (Dodson 1974a; Fedorenko 197%; Kerfoot 1977); when vertebrates are present the larger, more conspicuous invertebrate predators are replaced by smaller, less conspicuous ones (Dodson 1970, 1974a). These generalizations form the bases for recent conceptual models of zooplankton community structure (Dodson 1974a; Zaret in prep.). However, despite their success at predicting the distribution of different zooplankton species, these models are phenomenological in i Contribution 172 from the Limnological Research Center, University of Minnesota. 2 Work supported by National Science Foundation grant EMS 74-19490 to J. Shapiro. nature. The information they are based on does not allow a mechanistic interpretation of zooplankton community structure. For instance, while it is well documented that large herbivores disappear when vertebrate planktivores are introduced to a community, no data exist to determine whether their extinction is entirely a result of direct removal by vertebrates. It is possible that vertebrates, through their effects on the rest of the community, may impose other deleterious conditions on the large herbivores (e.g. increased competition with riewly established smaller herbivores). Furthermore, there is no direct evidence that invertebrate predation can be sufficient to cause extinction of small herbivores. Finally, the role of herbivore competition in structuring zooplankton communities is poorly understood (Lynch 1977a), and nothing is known about competition between invertebrate predators. To eliminate these ambiguities in interpreting zooplankton community structure, I examined simultaneously the predatory and competitive interactions in the community of a small Minnesota pond. Here I report on the mechanisms determining the relative abundances of species in this pond and show that the

TOPOI and rhetorical competence

Abstract: This essay argues that the speech communication scholar can make genuinely original contributions to the general study of communicative development, particularly to the investigation of strategic communication. The thesis advanced is that speech communication scholars need to return their attention to message strategies, but within the framework of the underlying cognitive and cultural structures through which they are created.

Variations on a theme of nuclear matter

Abstract: The authors review new techniques developed to apply the variational method to the nuclear matter problem. The variational wave function is taken to be ($S{\ensuremath{\Pi}}_{ilj}{\mathrm{F}}_{\mathrm{ij}}$) $\ensuremath{\Phi}$; the correlation operators ${\mathrm{F}}_{\mathrm{ij}}$ can in principle induce central, backflow, spin isospin, tensor, etc. correlations, and $\ensuremath{\Phi}$ is the ideal Fermi gas wave function. The application of diagrammatic cluster expansion and chain summation techniques to calculate expectation values with such wave functions is discussed in detail. The authors also give a brief overview of various other approaches to the calculation of the binding energies of quantum fluids, and a comparison of results for simple systems such ad helium liquids. Results obtained by various methods for simplified models of nuclear matter, which include central, spin, isospin, and tensor forces, have converged significantly in recent months. Results obtained with more realistic models which include the spin-orbit potentials are also discussed. The potential models considered so far either give too little binding or too high equilibrium density.

Exact penalty functions in nonlinear programming

Abstract: It is shown that the existence of a strict local minimum satisfying the constraint qualification of [16] or McCormick's [12] second order sufficient optimality condition implies the existence of a class of exact local penalty functions (that is ones with a finite value of the penalty parameter) for a nonlinear programming problem. A lower bound to the penalty parameter is given by a norm of the optimal Lagrange multipliers which is dual to the norm used in the penalty function.

Ultrasonic absorption and attenuation in mammalian tissues

Abstract: The ultrasonic absorption was determined, by the transient thermoelectric method, for brain, heart, kidney, liver, tendon, and testis from cat, mouse, pig and beef. Comparison of these absorption (α) values with published values of attenuation ( A ) shows: (1) that the α and A coefficients have nearly the same frequency dependencies in the range 0.5–7 MHz, (2) that the magnitudes of α and A differ appreciably and that difference depends upon the method of measurement and tissue type, and (3) that there appears to be little species difference, at least as revealed by measurement of liver and tendon.

Functional heterogeneity in a multipinnate muscle

Abstract: Many mammalian muscles have a complex internal architecture. This type of structure could allow a single muscle to produce a variety of force vectors through selective regional contractions. This hypothesis was tested electromyographically in the multipinnate pig masseter by recording simultaneously from several intramuscular sites. It was found that the activity in different portions of the masseter varied systematically during the various phases of mastication. anatomical correlates of the differential activity included fasciculus orientation and length, sarcomere length in specific jaw positions, and histochemical fiber type. The usual assumptions made about muscles for biomechanical analysis, such as uniform contraction and constant line of action, are inappropriate for complex muscles such as the pig masseter.

Evolution of temperate fruit/bird interactions: phenological strategies

Abstract: Evolving relationships between animals and plants are often patchy in their occurrence in both space and time. If the relationship is mutualistic, selection should act to maximize the probability of interaction between the participants. In the mutualistic interactions between temperate fleshy fruits and birds, the timing of fruit ripening affects the probability of seed dispersal by birds. Rapid removal of ripe fruits is important for some summer and fall fruiting species because of a high probability of fruit destruction by invertebrates (Thompson and Willson, 1978). Production of fruits at a time when birds do not remove them may be selectively disadvantageous in that destruction by invertebrates precludes successful dispersal. Therefore, bird-dispersed plants in temperate regions are commonly supposed to ripen their fruits in fall, after the avian breeding season during which birds often concentrate on insects (Morton, 1973) and during the fall migration (Snow, 1971; Stebbins, 1971). This paper examines the selective pressures acting on the seasonal timing of mutualistic interactions between temperate fleshy fruits and birds. Specifically, it (1) compares the removal rates of mid-latitude fruits before, during and after fall bird migrations, (2) analyzes seasonal variation in the ripening patterns of plants in the context of frugivore availability, and (3) provides a theoretical framework for future work on the phenology of temperate fruit/bird interactions. A fleshy

Cerebellar plasticity: modification of Purkinje cell structure by differential rearing in monkeys

Abstract: Dendritic branching in Purkinje and granule cells and the diameters of Purkinje cell somas were compared in several cerebellar areas of monkeys reared in isolation, with social experience, or in a large colony. In the colony-reared monkeys, spiny branchlets of Purkinje cells were more extensive in the paraflocculus and the nodulus than they were in the other two groups. Granule cell dendritic branching in the paraflocculus and nodulus did not differ across groups. In addition, Purkinje cell somas were larger in the uvula and the nodulus of the colony animals than in the other groups. These data indicate that the social and physical environment during development influences the morphology of cerebellar Purkinje cells.