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Showing papers by "University of Illinois at Urbana–Champaign published in 1974"


Book
01 Jan 1974
TL;DR: The report on the Thirteenth International Conference held at the Naval Postgraduate School, Monterey, California, United States of America, 13-18 April 1997 as discussed by the authors was published in 1997.
Abstract: Report on the Thirteenth International Conference held at the Naval Postgraduate School, Monterey, California, United States of America, 13-18 April 1997.

900 citations


Journal ArticleDOI
TL;DR: The modification described utilizes a serum bottle closed with a butyl rubber stopper with a crimped metal seal for the growth of obligately anaerobic bacteria.
Abstract: The modification described utilizes a serum bottle closed with a butyl rubber stopper with a crimped metal seal for the growth of obligately anaerobic bacteria.

821 citations


Journal ArticleDOI
TL;DR: The hypochromicity, as a function of temperature for 19 oligoribonucleotides capable of forming perfectly base-paired double helices, is used to extract thermodynamic parameters of helix formation.

715 citations


Journal ArticleDOI
TL;DR: Centrifugation of heparinized human blood on discontinuous gradients of Ficoll-Hypaque resulted in the simultaneous separation of mononuclear leukocytes, granulocytes, and erythrocytes with high recovery of each cell type.

715 citations


Journal ArticleDOI
TL;DR: Kinetic properties of soybean net photosynthetic CO(2) fixation and of the carboxylase and oxygenase activities of purified soybean ribulose 1, 5-diphosphate carboxyase were examined and showed equality of kinetic constants, consistent with the notion that the same enzyme catalyzes both reactions.
Abstract: Kinetic properties of soybean net photosynthetic CO(2) fixation and of the carboxylase and oxygenase activities of purified soybean (Glycine max [L.] Merr.) ribulose 1, 5-diphosphate carboxylase (EC 4.1.1.39) were examined as functions of temperature, CO(2) concentration, and O(2) concentration. With leaves, O(2) inhibition of net photosynthetic CO(2) fixation increased when the ambient leaf temperature was increased. The increased inhibition of CO(2) fixation at higher temperatures was caused by a reduced affinity of the leaf for CO(2) and an increased affinity of the leaf for O(2). With purified ribulose 1,5-diphosphate carboxylase, O(2) inhibition of CO(2) incorporation and the ratio of oxygenase activity to carboxylase activity increased with increased temperature. The increased O(2) sensitivity of the enzyme at higher temperature was caused by a reduced affinity of the enzyme for CO(2) and a slightly increased affinity of the enzyme for O(2). The similarity of the effect of temperature on the affinity of intact leaves and of ribulose 1,5-diphosphate carboxylase for CO(2) and O(2) provides further evidence that the carboxylase regulates the O(2) response of photosynthetic CO(2) fixation in soybean leaves. Based on results reported here and in the literature, a scheme outlining the stoichiometry between CO(2) and O(2) fixation in vivo is proposed.Oxygen competitively inhibited carboxylase activity with respect to CO(2), and CO(2) competitively inhibited oxygenase activity with respect to O(2). Within the limits of experimental error, the Michaelis constant (CO(2)) in the carboxylase reaction was identical with the inhibition constant (CO(2)) in the oxygenase reaction, and the Michaelis constant (O(2)) in the oxygenase reaction was identical with the inhibition constant (O(2)) in the carboxylase reaction. The Michaelis constant, (ribulose 1,5-diphosphate) was the same in both the carboxylase and oxygenase reactions. This equality of kinetic constants is consistent with the notion that the same enzyme catalyzes both reactions.

641 citations


Journal ArticleDOI
15 Mar 1974-Science
TL;DR: The detoxification mechanisms of mercury are used as examples to demonstrate that there are biological cycles for the synthesis and degradation of toxic compounds and that the present knowledge of the biologial cycles of toxic elements enables us to predict the behavior of other toxic elements in the environment.
Abstract: Some of the chemical and biochemical transformations of toxic elements in the environment are discussed with special emphasis on the role played by microorganisms. When confronted with a toxic substance, microorganisms frequently adapt to detoxify it. However, the detoxification of a substance by microorganisms can yield a product that is either more or less toxic to higher organisms. The detoxification mechanisms of mercury are used as examples to demonstrate that there are biological cycles for the synthesis and degradation of toxic compounds. It is also shown that our present knowledge of the biologial cycles of toxic elements enables us to predict the behavior of other toxic elements in the environment.

608 citations


Journal ArticleDOI
01 Nov 1974
TL;DR: In this paper, the authors consider the convergence of a gradient projection method to a conjugate direction with a quasi-Newton or Newton's method and achieve the attendant superlinear convergence rate.
Abstract: This paper considers some aspects of a gradient projection method proposed by Goldstein [1], Levitin and Polyak [3], and more recently, in a less general context, by McCormick [10]. We propose and analyze some convergent step-size rules to be used in conjunction with the method. These rules are similar in spirit to the efficient Armijo rule for the method of steepest descent and under mild assumptions they have the desirable property that they identify the set of active inequality constraints in a finite number of iterations. As a result the method may be converted towards the end of the process to a conjugate direction, quasi-Newton or Newton's method, and achieve the attendant superlinear convergence rate. As an example we propose some quadratically convergent combinations of the method with Newton's method. Such combined methods appear to be very efficient for large-scale problems with many simple constraints such as those often appearing in optimal control.

524 citations


Journal ArticleDOI
18 Jan 1974-Science
TL;DR: The toxic trace elements arsenic, antimony, cadmium, lead, selenium, and thallium were found to be most concentrated in the smallest respirable particles emitted from coal-fired power plants.
Abstract: The toxic trace elements arsenic, antimony, cadmium, lead, selenium, and thallium were found to be most concentrated in the smallest respirable particles emitted from coal-fired power plants. These elements, or their compounds, are probably volatilized during combustion and preferentially adsorb or condense onto the small particles which can most easily pass through conventional control equipment.

392 citations


Book ChapterDOI
01 Jan 1974

363 citations


Journal ArticleDOI
TL;DR: Environmental and dietary stress markedly alter the gastrointestinal microbiota in mice, and such stressful conditions profoundly affect the factors that regulate the localization and population levels of microorganisms in the stomach and intestines.
Abstract: Aerobic and anaerobic cultural techniques and histological methods were used in a study of the effects of environmental and dietary stress on the indigenous microbiota of the gastrointestinal tract of mice. Mice previously inoculated with Salmonella typhimurium were examined in a similar manner. Three strains of mice (CD-1, Ha/ICr, and C57BL) were used. Control animals previously inoculated with S. typhimurium had low population levels of Salmonella bacteria in the small and large bowel. Mice previously inoculated with Salmonella and then deprived of food, water, and bedding for 48 h harbored high population levels of these bacteria in their small and large bowels. Coliforms increased in numbers in the large bowel of stressed mice inoculated with Salmonella and in the jejunum-ileum and cecum of stressed mice not previously inoculated with Salmonella. Control mice had high population levels of lactobacilli inhabiting the keratinized squamous epithelium of the stomach. Stressed mice showed dramatic reductions in these populations of lactobacilli. Populations of fusiform-shaped bacteria associated with the mucosal epithelium of the cecum and colon in control mice were reduced in stressed mice as determined by microscope examination of histological sections. Total anaerobic counts were similar, however, in both stressed and control animals. Environmental and dietary stress markedly alter the gastrointestinal microbiota in mice. Therefore, such stressful conditions profoundly affect the factors that regulate the localization and population levels of microorganisms in the stomach and intestines.

327 citations


Journal ArticleDOI
TL;DR: In this article, a progress report on the structure and reactions of hydroxamic acids and N-hydroxyimides is presented, and some of the biological activities of these compounds are surveyed.
Abstract: This progress report is concerned primarily with problems relating to the structure and reactions of hydroxamic acids and N-hydroxyimides, and also surveys some of the biological activities of these compounds. Particular significance attaches to the Lossen rearrangement of O-acylated hydroxamic acids, which leads to isocyanates or their reaction products.

Journal ArticleDOI
TL;DR: In this article, the authors test the view that organization structure and process are related to organizational climate which in turn is related to organization performance and employee job satisfaction, and find that several organizational process variables (but no structural variables) were significantly related to the climate of the organization as perceived by scientists.

Journal ArticleDOI
TL;DR: This paper deals with a combinatorial minimization problem arising from studies on multimodule memory organizations with a particular solution proposed and it is demonstrated that it is close to optimum.
Abstract: This paper deals with a combinatorial minimization problem arising from studies on multimodule memory organizations. Instead of searching for an optimum solution, a particular solution is proposed and it is demonstrated that it is close to optimum. Lower bounds for the objective functions are obtained and compared with the corresponding values of the particular solution. The maximum percentage deviation of this solution from optimum is also established.

Journal ArticleDOI
TL;DR: In this paper, the parameters affecting strength development in compacted cylinders of 3CaOSiO2 and β-2CaO- SiO2 mortars exposed to CO2 were investigated.
Abstract: The parameters affecting strength development in compacted cylinders of 3CaO- SiO2 and β-2CaO- SiO2 mortars exposed to CO2 were investigated. Strength increased with time up to 81 min, the duration of the longest detailed study. The β-2CaO- SiO2 develops strength more slowly initially, but both silicates achieved compressive strengths of 7,000 to 10,000 psi. The rate of increase in strength depends on both the amount of water used in molding the compact and the amount of water present in the CO2. Increasing CO2 pressures from 1 to 2 atm increased the rate of reaction, but a further increase to 4 atm had little additional effect. Carbonation occurs mainly in the outer portions of the cylindrical compacts. The initial reaction on exposure to CO2 appears to be accelerated hydration of the silicates to a CaO-SiO2-H2O-like gel and calcite. The gel has a stoichiometry similar to that found in conventional hydration. Further reaction results in progressive carbonation of the gel, which decreases its lime content. The reaction products appear to be intimately dispersed in the microstructure.

Journal ArticleDOI
TL;DR: In the Machine Age science not only took the world apart, but it took itself apart, dividing itself into narrower and narrower disciplines as mentioned in this paper, each discipline represented a different way of looking at the same world.
Abstract: In the Machine Age science not only took the world apart, but it took itself apart, dividing itself into narrower and narrower disciplines. Each discipline represented a different way of looking at the same world. Shortly before World War II science began to put itself back together again so that it could study phenomena as a whole, from all points of view. As a result, a host of new interdisciplines emerged such as Operations Research, Cybernetics, Systems Engineering, Communications Sciences, and Environmental Sciences. Unlike earlier scientific disciplines which sought to separate themselves from each other and to subdivide; the new interdisciplines seek to enlarge themselves, to combine to take into account more and more aspects of reality. Systems Science is the limit of this process, an amalgamation of all the parts of science into an integrated whole. Thus, Systems Science is not a science, but is science taken as a whole and applied to the study of wholes.




Journal ArticleDOI
TL;DR: Coenzyme M is a recently discovered cofactor which is involved in methyl transfer reactions in Methanobacterium and evidence indicates that an active form of this cofactor is 2-mercaptoethanesulfonic acid which is methylated producing 2-(methylthio) ethanesulfonics acid.

Journal ArticleDOI
TL;DR: In this article, a new way to bracket the characteristic temperatures T 0 (where ΔGpc → M = 0 when T = T0) and T 0 − where ΔGMc→ p + ΔGMnc → p = 0 in the case of T − and T − where T − is defined as the temperature range over which thermoelastic behavior occurs.

Journal ArticleDOI
TL;DR: The results indicate the great biosynthetic ability of these organisms and suggest that, in their ecological niche within the large intestine, many nutrients are in very low supply, whereas materials such as ammonia, heme, and vitamin B(12), or related compounds, must be available during much of the time.
Abstract: Studies of three reference strains of Bacteroides fragilis subsp. fragilis showed that they grow well in a minimal defined medium containing glucose, hemin, vitamin B12, minerals, bicarbonate-carbon dioxide buffer, NH4Cl, and sulfide. The vitamin B12 requirement of 0.1 ng/ml was replaced with 7.5 μg of methionine. Cysteine or sulfide was an excellent source of sulfur, thioglycolate was a poor source, and thiosulfate, methionine, β-mercaptoethanol, dithiothreitol, sulfate, or sulfite did not serve as sole sources of sulfur. Neither single amino acids, nitrate, urea, nor a complex mixture of L-amino acids or peptides effectively replaced ammonia as the nitrogen source. Comparative studies with a few strains of other subspecies of B. fragilis including B. fragilis subsp. vulgatus, B. fragilis subsp. thetaiotaomicron, and B. fragilis subsp. distasonis indicate that they exhibit similar growth responses in the minimal medium. A single strain of B. fragilis subsp. ovatus required other materials. The results indicate the great biosynthetic ability of these organisms and suggest that, in their ecological niche within the large intestine, many nutrients such as amino acids are in very low supply, whereas materials such as ammonia, heme, and vitamin B12, or related compounds, must be available during much of the time.

Journal ArticleDOI
TL;DR: The average period and wavelength computed by the power-spectrum method are 4.5 days and 3800 km and for the compositing analysis 3.8 days and 3100 km.
Abstract: This study uses both spectral and compositing analyses to determine the structure of North African easterly waves during the summers of 1968 and 1969. The average period and wavelength computed by the power-spectrum method are 4.5 days and 3800 km and for the compositing analysis 3.8 days and 3100 km. Although the period and wavelength of individual waves vary considerably, the spectral results are in qualitative agreement with the compositing results except in extreme northern Africa where eastward-moving disturbances of the same period affect the spectral computations. The maximum surface amplitudes of u, v, p and Td associated with the waves occur about 20N near the mean location of the east-west oriented region of minimum surface pressure. East of the Greenwich meridian the amplitude decreases and the wave motion is barely detectable with surface data near 25E. The compositing results show that the waves influence latitudes between 5 and 3ON and that wave features tilt from southwest to north...

Journal ArticleDOI
08 Nov 1974-Science
TL;DR: The data suggest that in the potentials studied there is a component associated with the preparation to perform a specific movement, rather than with generalized preparatory processes.
Abstract: Eleven subjects squeezed an electronic dynamometer, at each of three force levels, with both their right and left hands. In right-handed subjects the premovement "readiness" potentials were larger over the hemisphere contralateral to the responding hand. Left-handed subjects show contralateral dominance when responding with the right hand but not when responding with the left hand. The data suggest that in the potentials studied there is a component associated with the preparation to perform a specific movement, rather than with generalized preparatory processes.

Book ChapterDOI
TL;DR: This chapter presents a description of the general and developmental theories of memory, with specific relation to retardation, and the place of deliberate strategies, control processes, or organization schemes within these theories is discussed.
Abstract: Publisher Summary This chapter discusses the role of strategic behavior in retardate memory. Efficient performance on a variety of memory tasks relies on the effective use of certain plans schemes or mnemonic strategies. By the appropriate exploitation of various strategies, it is possible to organize and transform the random input of information into manageable information-rich units. Because it is as easy to remember a considerable amount of material in information-rich units as it is to remember a small amount of material in informationally impoverished units, it is economical to employ such strategies and plans in order to make the most effective use of a limited-capacity memory system. An examination of the theoretical and empirical developments, concerning the use of plans and strategies by young and retarded children, is discussed in this chapter. It presents a description of the general and developmental theories of memory, with specific relation to retardation. The place of deliberate strategies, control processes, or organization schemes, within these theories, is discussed in the chapter. A brief review of the empirical findings, implicating a strategic deficit in a wide variety of tasks and situations, is also discussed in this chapter. Two programs of research from author's laboratory and the implications of this research for educational practice are described in the chapter.

Journal ArticleDOI
TL;DR: In this article, the authors present reaction rate constants for anaerobic fermentation of domestic refuse and evaluate the effect of temperature on the rate of methane fermentation using the Monod model.
Abstract: Anaerobic fermentation of organic solid waste can provide a significant source of fuel gas (methane). Application of this process requires a better understanding of the kinetics of the biological system. The literature is replete with kinetic studies of this process as applied to waste solids from water pollution control systems. Much of this work has been conducted in the mesophilic temperature range. Increased temperatures yield higher reaction rates that will improve the economics of the process. The rate limiting step in the fermentation of refuse is the hydrolysis of the complex organic solids, in particular cellulose. Cellulose is a major component of the refuse. A laboratory study employing domestic refuse has shown the effect of temperature on the rate of methane fermentation. The optimum mesophilic temperature was found to be 42°C, while the optimum thermophilic temperature was at least 60°C. No data was obtained beyond the 60°C temperature. Reaction rate constants are presented for anaerobic fermentation of domestic refuse. Because of the characteristics of the substrate it−was not possible to obtain the necessary measurements for evaluation of constants in the Monod model. An overall system constant was developed.

Journal ArticleDOI
TL;DR: In this paper, the long-time dependence of the time correlation functions is taken to be Gaussian, and the resulting short and long time parts are joined together in a manner similar to that used by Gulley, Hone, Scalapino, and Silbernagel.
Abstract: Electron-spin-resonance (ESR) measurements are reported in the two-dimensional Heisenberg magnet ${\mathrm{K}}_{2}$Mn${\mathrm{F}}_{4}$ and compared with a theory developed here. Results are in excellent agreement with calculated values and, we feel, give strong confirmation of recent theories of spin dynamics. The theory treats the linewidth $\ensuremath{\Delta}H$ and line shape in a two-dimensional Heisenberg system by assuming diffusive motion for the long-time dependence of the time correlation functions. The short-time dependence is taken to be Gaussian, and the resulting short- and long-time parts are joined together in a manner similar to that used by Gulley, Hone, Scalapino, and Silbernagel. An angular dependence roughly of the form $\ensuremath{\Delta}H\ensuremath{\propto}{(3{cos}^{2}\ensuremath{\theta}\ensuremath{-}1)}^{2}+(\mathrm{const}.)$ ($\ensuremath{\theta}$ is the angle of dc field with respect to the perpendicular to the plane) is observed at high temperature, as predicted by the theory. This angular dependence cannot be explained by either the secular or nonsecular parts of the second moment. Rather, it is due explicitly to the dominance of wave-vector $q\ensuremath{\rightarrow}0$ modes in the long-time decay of correlations in a two-dimensional system. As temperature is lowered toward the antiferromagnetic ordering temperature ${T}_{N}=45$ \ifmmode^\circ\else\textdegree\fi{}K, the linewidth initially decreases, passes through a minimum, and then increases rapidly near ${T}_{N}$. The angular dependence is also temperature-dependent such that $\ensuremath{\Delta}H$ ($\ensuremath{\theta}=90\ifmmode^\circ\else\textdegree\fi{}$) becomes less than $\ensuremath{\Delta}H$ ($\ensuremath{\theta}=55\ifmmode^\circ\else\textdegree\fi{}$) below about 65 K. These features of the temperature dependence are consistent with the theory. Indeed, we find absolute agreement between theory and experiment to within 20% or better at all angles over a broad range of temperature. The theory contains no adjustable parameters since classical dipolar coupling is taken as the sole source of broadening and we use the same exchange constant $J$ as obtained from susceptibility measurements. The room-temperature line shape, which is Lorentzian at $\ensuremath{\theta}=55\ifmmode^\circ\else\textdegree\fi{}$ and non-Lorentzian at $\ensuremath{\theta}=90\ifmmode^\circ\else\textdegree\fi{}$, and the frequency dependence of $\ensuremath{\Delta}H$, measured at 9.8 and 23.4 GHz, are also in agreement with theory. Shift of the resonance field with angle has been measured as well. This effect can be explained quantitatively by the net dipolar field and, contrary to the other phenomena, does not, in the main, reflect two-dimensional spin dynamics.

Journal ArticleDOI
TL;DR: In this article, principal probability concepts are presented and developed for the proper modeling and analysis of uncertainty, and for evaluating the associated effects on safety and design, and specific proposals for evaluating safety level and for developing safety and load factors for design are developed.
Abstract: Principal probability concepts are presented and developed for the proper modeling and analysis of uncertainty, and for evaluating the associated effects on safety and design. Under conditions of uncertainty, safety and serviceability of structures can be assured only in terms of the probability of survival (or conversely of failure); accordingly, the level of safety is expressed explicitly as a function of the degree of uncertainty. The assumptions necessary to implement probability concepts in the development of practical design criteria and code provisions are explained and delineated. Uncertainty (including uncertainty associated with errors in estimation and imperfection in mathematical models) is expressed in terms of the coefficient of variation; in this term, its effect on safety and design can be assessed systematically and logically through first-order statistical analysis. Specific proposals for evaluating safety level and for developing safety and load factors for design are developed.

Journal ArticleDOI
TL;DR: The nature of the polar head-group and the hydrocarbon chain thus both have an effect on the hydration of phospholipids.

Journal ArticleDOI
TL;DR: Results of the study of light and electron micrographs suggest that the microorganisms localize on epithelial surfaces in various areas of the digestive tracts of animals are procaryotic, and that they interact with small bowel epithelial cells to form an attachment site.
Abstract: Some indigenous microorganisms localize on epithelial surfaces in various areas of the digestive tracts of animals. One of these, a segmented, filamentous microbe, localizes on the epithelium in the small bowels of mice and rats. These filamentous microbes colonize mice at weaning time and persist in adult animals for at least 2 months. Results of the study of light and electron micrographs suggest that the microorganisms are procaryotic, and that they interact with small bowel epithelial cells to form an attachment site. This site consists of modified epithelial cell membrane and apical cytoplasm adjacent to the attached bacterium. The microbe fills the site with part of its first segment. This segment has a nipple-like appendage on the end inserted into the epithelial cell. The other segments, which compose the rest of the filament, are usually separated by septa. Many of the individual segments contain intrasegmental bodies that appear to be procaryotic cells. Some of these intrasegmental bodies are similar in morphology to the first segment of each filament inserted into an epithelial cell. These intracellular bodies may be components in the life cycle of the microorganism. The organism has not yet been cultured in recognizable form. Therefore, such a hypothesis cannot be proved as yet, nor can the microbe be classified with certainty. Because it localizes in an epithelial habitat in the small bowel, however, it may be a particularly important microbial type in the gastrointestinal ecosystem of laboratory rodents.

Journal ArticleDOI
TL;DR: The study of chloroplasts isolated from sunflower leaves suggests that chloroplast electron transport begins to limit photosynthesis at leaf water potentials below about -11 bars, and suggests that, during severe desiccation, the limitation may shift from electron transport to photophosphorylation.
Abstract: Cyclic and noncyclic photophosphorylation and electron transport by photosystem 1, photosystem 2, and from water to methyl viologen ("whole chain") were studied in chloroplasts isolated from sunflower (Helianthus annus L. var Russian Mammoth) leaves that had been desiccated to varying degrees. Electron transport showed considerable inhibition at leaf water potentials of -9 bars when the chloroplasts were exposed to an uncoupler in vitro, and it continued to decline in activity as leaf water potentials decreased. Electron transport by photosystem 2 and coupled electron transport by photosystem 1 and the whole chain were unaffected at leaf water potentials of -10 to -11 bars but became progressively inhibited between leaf water potentials of -11 and -17 bars. A low, stable activity remained at leaf water potentials below -17 bars. In contrast, both types of photophosphorylation were unaffected by leaf water potentials of -10 to -11 bars, but then ultimately became zero at leaf water potentials of -17 bars. Although the chloroplasts isolated from the desiccated leaves were coupled at leaf water potentials of -11 to -12 bars, they became progressively uncoupled as leaf water potentials decreased to -17 bars. Abscisic acid and ribonuclease had no effect on chloroplast photophosphorylation. The results are generally consistent with the idea that chloroplast activity begins to decrease at the same leaf water potentials that cause stomatal closure in sunflower leaves and that chloroplast electron transport begins to limit photosynthesis at leaf water potentials below about -11 bars. However, it suggests that, during severe desiccation, the limitation may shift from electron transport to photophosphorylation.