Showing papers by "University of Colorado Boulder published in 1983"
TL;DR: In this article, the authors describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer.
Abstract: We describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer. High sensitivity for detection of resonance information is achieved by optical heterodyne detection with sidebands produced by rf phase modulation. Physical, optical, and electronic aspects of this discriminator/laser frequency stabilization system are considered in detail. We show that a high-speed domain exists in which the system responds to the phase (rather than frequency) change of the laser; thus with suitable design the servo loop bandwidth is not limited by the cavity response time. We report diagnostic experiments in which a dye laser and gas laser were independently locked to one stable cavity. Because of the precautions employed, the observed sub-100 Hz beat line width shows that the lasers were this stable. Applications of this system of laser stabilization include precision laser spectroscopy and interferometric gravity-wave detectors.
3,393 citations
TL;DR: The RNA moieties of ribonuclease P purified from both E. coli and B. subtilis can cleave tRNA precursor molecules in buffers containing either 60 mM Mg2+ or 10 mM MG2+ plus 1 mM spermidine, and in vitro, the RNA and protein subunits from one species can complement sub units from the other species in reconstitution experiments.
2,524 citations
TL;DR: In this paper, the authors discuss the relationships between stage of development in organizational life cycles and organizational effectiveness and conclude that major criteria of effectiveness change in predictable ways as organizations develop through their life cycles.
Abstract: This paper discusses the relationships between stage of development in organizational life cycles and organizational effectiveness. We begin the paper by reviewing nine models of organizational life cycles that have been proposed in the literature. Each of these models identifies certain characteristics that typify organizations in different stages of development. A summary model of life cycle stages is derived that integrates each of these nine models.
Next, a framework of organizational effectiveness developed by Quinn and Rohrbaugh is introduced. This framework organizes criteria of effectiveness into four models-rational goal, open systems, human relations, and internal processes models. We hypothesize that certain of the models are important in evaluating the effectiveness of organizations in particular life cycle stages but not in others. The analysis of a state agency's development over five years provides some evidence to support these hypothesized relationships between life cycle stages and criteria of effectiveness.
We conclude that major criteria of effectiveness change in predictable ways as organizations develop through their life cycles. Some shifts in state of development are resisted by the organization much more than are others, and intervention into organizations may be needed to help make the transitions less painful and costly. We also discuss why the predictions of contingency theory often are not substantiated by research because the responses of organizations to the external environment vary in different life cycle stages.
1,693 citations
TL;DR: High-voltage electron microscopy after detergent extraction of human epidermal keratinocyte (HK) colonies grown in the defined medium with low and high calcium has revealed specific changes in the intermediate filament network and keratohyalin granules corresponding to changes in cellular differentiation.
1,096 citations
TL;DR: The pronounced directional selectivity of CS cells, at least in the present environment, suggests that they fire in response to complex, but specific, stimulus features in the extramaze world rather than to absolute place in a non-egocentric space.
Abstract: Isolated single units in rat dorsal hippocampus and fascia dentata were classified as 'Theta' or 'Complex-Spike' cells, and their firing characteristics were examined with respect to position, direction and velocity of movement during forced choice, food rewarded search behavior on a radial eight arm maze. Most spikes from CS cells occurred when the animal was located within a particular place on the maze and moving in a particular direction. Theta cells had very low spatial selectivity. Both cell categories had discharge probabilities which increased somewhat as a function of running velocity but tended to asymptote well before half-maximal velocity. The place/direction specificity of CS cells was significantly higher in CA1 than in CA3 and CA3 CS cells exhibited a striking preference for the inward radial direction. The pronounced directional selectivity of CS cells, at least in the present environment, suggests that they fire in response to complex, but specific, stimulus features in the extramaze world rather than to absolute place in a non-egocentric space. An alternative possibility is that the geometrical constraints of the maze surface have a profound influence on the shapes of the response fields of CS cells.
964 citations
TL;DR: The most common sources of bacteremia were the respiratory, genitourinary, and gastrointestinal tracts; however, the source was unknown in nearly one-third of episodes.
Abstract: Five hundred episodes of septicemia were reviewed, with emphasis on laboratory and epidemiologic findings. The isolation of facultative and anaerobic gram-negative bacilli, fungi, and gram-positive cocci (except viridans streptococci and Staphylococcus epidermidis) almost always indicated true bacteremia, whereas the isolation of aerobic and anaerobic gram-positive bacilli, including Clostridium species, often represented contamination. More than 99% of all episodes were detected when two samples of blood (a total of 30 ml) were cultured. The five most common isolates were Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The incidence of septicemia was highest among medical patients and lowest among obstetric-gynecologic patients. Two-thirds of all episodes were nosocomial; S. aureus, enterococci, facultative gram-negative bacilli, and fungi were especially common nosocomial pathogens. The microorganisms isolated varied with the hospital service; polymicrobial episodes were especially common among surgical patients and transplant recipients. The most common sources of bacteremia were the respiratory, genitourinary, and gastrointestinal tracts; however, the source was unknown in nearly one-third of episodes. Microorganisms causing septicemia in neutropenic and nonneutropenic patients were not different; however, polymicrobial infections were more frequent in the presence of neutropenia. After antimicrobial susceptibility data became available, therapy was appropriate greater than 90% of the time.
719 citations
TL;DR: In this article, various deoxynucleoside N,N-dialkylaminomethoxyphosphines were examined for stability and reactivity in deoxyoligonucleotide synthesis.
556 citations
TL;DR: The results suggest that P-granule segregation does not require either the spindle or cytoplasmic microtubules, but that this process as well as generation of other asymmetries does require cytoskeletal functions that depend on microfilaments.
543 citations
TL;DR: A new method is described for the recording and discrimination of extracellular action potentials in CNS regions with high cellular packing density or where there is intrinsic variation in action potential amplitude during burst discharge based on the principle that cells with different ratios of distances from two electrode tips will have different spike-amplitude ratios when recorded on two channels.
490 citations
TL;DR: The data imply that the antimicrobial activity of glycinol, glyceollin, and coumestrol are due to a general interaction with the bacterial membrane, which is different from that of the other phytoalexins examined.
Abstract: The biochemical basis for the ability of the pterocarpan phytoalexin glycinol (3,6a,9-trihydroxypterocarpan) to inhibit the growth of bacteria was examined. Glycinol at bacteriostatic concentrations ( e.g. 50 micrograms per milliliter) inhibits the ability of Erwinia carotovora to incorporate [ 3 H]leucine, [ 3 H]thymidine, or [ 3 H]uridine into biopolymers. Exposure of Escherichia coli membrane vesicles to glycinol at 20 micrograms per milliliter results in inhibition of respiration-linked transport of [ 14 C]lactose and [ 14 C]glycine into the vesicles when either d-lactate or succinate is supplied as the energy source. The ability of E. coli membrane vesicles to transport [ 14 C]α-methyl glucoside, a vectorial phosphorylation-mediated process, is also inhibited by glycinol at 20 micrograms per milliliter. Furthermore, exposure of membrane vesicles to glycinol (50 micrograms per milliliter) at 20°C results in the leakage of accumulated [ 14 C]α-methyl glucoside-6-phosphate. The effects of the phytoalexins glyceollin, capsidiol, and coumestrol, and daidzein, a compound structurally related to glycinol but without antibiotic activity, upon the E. coli membrane vesicle respiration-linked transport of [ 14 C]glycine and of [ 14 C]α-methyl glucoside was also examined. Glyceollin and coumestrol (50 micrograms per milliliter), but not daidzein, inhibit both membrane-associated transport processes. These data imply that the antimicrobial activity of glycinol, glyceollin, and coumestrol are due to a general interaction with the bacterial membrane. Capsidiol (50 micrograms per milliliter) inhibits d-lactate-dependent transport of [ 14 C]glycine but not vectorial phosphorylation-mediated transport of [ 14 C]α-methyl glucoside. Thus, capsidiol9s mechanism of antimicrobial action seems to differ from that of the other phytoalexins examined.
488 citations
TL;DR: Although some adverse prognostic factors are not amenable to intervention, prevention of nosocomial bacteremia and fungemia and early reversal of hypotension may reduce the death rate from sepsis.
Abstract: Among 500 patients with bacteremia and fungemia, total mortality was 42%; about half of all deaths were attributable directly to infection. Mortality increased with age, but deaths unrelated to infection itself were responsible in part for this increase. Mortality was 2.6% among obstetric-gynecologic patients, 42% among medical patients, 49% among surgical patients, and 60% among transplant patients. The risk of death was especially high with enterococcal, facultative gram-negative, fungal, polymicrobial, or hospital-acquired sepsis; in the presence of shock, leukopenia, absolute granulocytopenia, or defined predisposing conditions (neoplasia, cirrhosis, and combinations of factors such as surgery and renal failure); and with a primary infected focus in the respiratory tract, the skin, a surgical wound, an abscess, or an unknown site. Body temperature was inversely related to mortality. Survival was increased by the use of appropriate antibiotics and, where applicable, additional therapeutic maneuvers (e.g., drainage). Multivariate analysis defined seven variables that independently influenced outcome: microorganism, blood pressure, body temperature, primary focus of infection, place of acquisition of infection, age, and predisposing factors. Although some adverse prognostic factors are not amenable to intervention, prevention of nosocomial bacteremia and fungemia and early reversal of hypotension may reduce the death rate from sepsis.
TL;DR: In this article, the electronic structure of six Cu-based ternary chalcopyrite semiconductors is calculated self-consistently for the first time within the density-functional formalism.
Abstract: The electronic structure of six Cu-based ternary chalcopyrite semiconductors is calculated self-consistently for the first time within the density-functional formalism. The chemical trends in the band structures, electronic charge densities, density of states, and chemical bonding are analyzed.
TL;DR: Lymphocyte proliferation in response to the mitogens phytohemagglutinin and concanavalin A was suppressed in the inescapableshock group but not in the escapable shock group, suggesting that the controllability of stressors is critical in modulating immune functioning.
Abstract: Rats were given series of escapable shocks, identical inescapable shocks, or no shock. The subjects were reexposed to a small amount of shock 24 hours later, after which an in vitro measure of the cellular immune response was examined. Lymphocyte proliferation in response to the mitogens phytohemagglutinin and concanavalin A was suppressed in the inescapable shock group but not in the escapable shock group. This suggests that the controllability of stressors is critical in modulating immune functioning.
TL;DR: In this paper, a methylation analysis procedure has been developed by which the glycosyl-linkage compositions of microgram quantities of complex carbohydrates, including those containing hexosyluronic acid residues, can be determined.
TL;DR: Urogenital mesenchyme induces specific epithelial morphogenesis, growth, and function within the genital tract and that the hormonal sensitivity of these morphogenetic processes resides in the mesenchYme that invariably contains nuclear hormone receptors.
Abstract: Publisher Summary
This chapter explains the role of mesenchymal–epithelial interactions in hormone induced morphogenesis and growth. The mechanism of steroid hormone action is thought to involve specific high-affinity receptor proteins. The hormone enters the cell, binds to the cytoplasmic receptor, which after activation translocates to the nucleus. The hormone–receptor complex in turn binds to nuclear acceptor sites on the chromatin. This activates a variety of metabolic processes, the most important being the stimulation of messenger RNA (mRNA) synthesis and the ultimate production of new proteins. The first indication that androgens can elicit their effects upon epithelial morphogenesis via the mediation of mesenchymal cells comes from studies in which urogenital epithelia from the embryonic seminal vesicle or urogenital sinus are grown in association with either urogenital mesenchyme or with non-target integumental mesenchyme. Urogenital mesenchyme induces specific epithelial morphogenesis, growth, and function within the genital tract and that the hormonal sensitivity of these morphogenetic processes resides in the mesenchyme that invariably contains nuclear hormone receptors. As morphogenetic processes are cyclic in adult genital tracts of many species, developmental properties are expressed in adulthood and, for this reason, appear to play a regulatory role in abnormal epithelial differentiation including carcinogenesis.
TL;DR: In this paper, a temperature-programmed desorption (TPD) experiment on a supported metal catalyst is described, where a small amount of catalyst (10-200 mg) is contained in a reactor that can be heated by a furnace.
Abstract: In a typical temperature-programmed desorption (TPD) experiment on a supported metal catalyst, a small amount of catalyst (10–200 mg) is contained in a reactor that can be heated by a furnace. An inert gas, usually helium at atmospheric pressure, flows over the catalyst. Following pretreatment to obtain a reduced catalyst, a gas is adsorbed on the surface, usually by pulse injections of the adsorbate into the carrier gas upstream from the reactor. After the excess gas is flushed out, the catalyst is heated to create a linear rise in temperature with time. A small thermocouple inserted in the catalyst measures the temperature and a detector downstream measures the change in the inert gas stream. The ideal detector is a mass spectrometer which measures the composition of the effluent stream as a function of catalyst temperature. Because of the high carrier-gas flow rate, the detector response is proportional to the rate of desorption if diffusion and readsorption are not limiting.
01 Dec 1983
TL;DR: A linear-time algorithm for the special case of the disjoint set union problem in which the structure of the unions (defined by a “union tree”) is known in advance, which gives similar improvements in the efficiency of algorithms for solving a number of other problems.
Abstract: This paper presents a linear-time algorithm for the special case of the disjoint set union problem in which the structure of the unions (defined by a “union tree”) is known in advance. The algorithm executes an intermixed sequence of m union and find operations on n elements in 0(m+n) time and 0(n) space. This is a slight but theoretically significant improvement over the fastest known algorithm for the general problem, which runs in 0(ma(m+n, n)+n) time and 0(n) space, where a is a functional inverse of Ackermann's function. Used as a subroutine, the algorithm gives similar improvements in the efficiency of algorithms for solving a number of other problems, including two-processor scheduling, the off-line min problem, matching on convex graphs, finding nearest common ancestors off-line, testing a flow graph for reducibility, and finding two disjoint directed spanning trees. The algorithm obtains its efficiency by combining a fast algorithm for the general problem with table look-up on small sets, and requires a random access machine for its implementation. The algorithm extends to the case in which single-node additions to the union tree are allowed. The extended algorithm is useful in finding maximum cardinality matchings on nonbipartite graphs.
TL;DR: Proposition d'une nouvelle methode de visualisation du transfert de chaleur dans un ecoulement de fluide. Application a la convection naturelle dans une enceinte carree chauffee lateralement
Abstract: Proposition d'une nouvelle methode de visualisation du transfert de chaleur dans un ecoulement de fluide. Application a la convection naturelle dans une enceinte carree chauffee lateralement
TL;DR: The results suggest that dodeca-alpha-1,4-d-galacturonid is the active elicitor, but the possibility remains that the active component could be a slightly modified oligogalacturonide present, but not detected, in the purified fractions.
Abstract: Elicitors of phytoalexin accumulation in soybean (Glycine max L. Merr., cv Wayne) cotyledons were released from soybean cell walls and from citrus pectin by partial acid hydrolysis. These two hydrolysates yielded nearly identical distributions of elicitor activity when fractionated on anion-exchange columns. Chromatography of the pectin elicitor on gel filtration and high-pressure anion-exchange columns did not further purify the elicitor. Elicitor activity of the preparation was lost by treatment with either endo-alpha-1,4-polygalacturonase or pectate lyase. Glycosyl residue compositions of the purified elicitors from cell walls and pectin were both found to be approximately 98% galacturonosyl residues. Linkage analysis of the pectin elicitor showed that most, if not all, of the galacturonosyl residues were alpha-1,4-linked. The high-mass molecular ions detected by fast atom bombardment-mass spectrometry of the most active elicitor fractions from cell walls and pectin both corresponded precisely to a molecule composed of 12 galacturonosyl residues. These results suggest that dodeca-alpha-1,4-d-galacturonide is the active elicitor, but the possibility remains that the active component could be a slightly modified oligogalacturonide present, but not detected, in the purified fractions.
TL;DR: This regulatory mechanism provides a rationale for the finding that the two photosystems are physically separated in chloroplast membranes (PS II in appressed, grana membranes, and PS I in nonappressed, stroma membranes).
Abstract: A chlorophyll-protein complex of chloroplast membranes, which simultaneously serves as light-harvesting antenna and membrane adhesion factor, undergoes reversible, lateral diffusion between appressed and nonappressed membrane regions under the control of a protein kinase. The phosphorylation-dependent migration process regulates the amount of light energy that is delivered to the reaction centers of photosystems I and II (PS I and PS II), and thereby regulates their rate of turnover. This regulatory mechanism provides a rationale for the finding that the two photosystems are physically separated in chloroplast membranes (PS II in appressed, grana membranes, and PS I in nonappressed, stroma membranes). The feedback system involves the following steps: a membrane-bound kinase senses the rate of PS II vs. PS I turnover via the oxidation-reduction state of the plastoquinone pool, which shuttles electrons from PS II via cytochrome f to PS I. If activated, the kinase adds negative charge (phosphate) to a grana-localized pigment-protein complex. The change in its surface charge at a site critical for promoting membrane adhesion results in increased electrostatic repulsion between the membranes, unstacking, the lateral movement of the complex to adjacent stroma membranes, which differ in their functional composition. The general significance of this type of membrane regulatory mechanism is discussed.
TL;DR: It is observed that visual feedback can affect the spatial accuracy of movement with durations much less than 190 msec, and it is hypothesized thatVisual feedback can aid motor control via processes not associated with intermittent error corrections.
Abstract: A major line of behavioral support for motor-program theory derives from evidence indicating that feedback does not influence the execution and control of limited duration movements. Since feedback cannot be utilized, the motor-program is assumed to act as the controlling agent. In a classic study, Keele and Posner observed that visual feedback had no effect on the accuracy of 190-msec single-aiming movements. Therefore visual feedback processing time is greater than 190 msec, and, more importantly, limited duration movements are governed by motor programs. In the present paper, we observed that visual feedback can affect the spatial accuracy of movements with durations much less than 190 msec. We hypothesize that visual feedback can aid motor control via processes not associated with intermittent error corrections.
TL;DR: In this article, a theoretical framework is offered that interprets Battig's conceptualization of contextual interference in terms of the multiple and variable processing that result from the concurrent presence of tasks in working memory.
Abstract: A theoretical framework is offered that interprets Battig's (1979) conceptualization of contextual interference in terms of the multiple and variable processing that result from the concurrent presence of tasks in working memory. The central role of cognitive processes in the learning of motor tasks and the influence of these processes on motor performance is emphasized. This theoretical interpretation switches emphasis away from a memorial representation of a motor act comprised of sensory attributes to an active, operationally defined representation.
TL;DR: The relationship between age-related changes in body physiology and certain acoustic characteristics of voice was studied in a sample of 48 men representing three chronological age groups (25, 35, and 60) as discussed by the authors.
Abstract: The relationship between age-related changes in body physiology and certain acoustic characteristics of voice was studied in a sample of 48 men representing three chronological age grouping (25–35,...
TL;DR: The intervening sequence of the Tetrahymena ribosomal RNA precursor is excised as a linear RNA molecule which subsequently cyclizes itself in a protein-independent reaction, analogous to that by which splicing of the precursor RNA is achieved.
Abstract: The intervening sequence (IVS) of the Tetrahymena ribosomal RNA precursor is excised as a linear RNA molecule which subsequently cyclizes itself in a protein-independent reaction. Cyclization involves cleavage of the linear IVS RNA 15 nucleotides from its 5' end and formation of a phosphodiester bond between the new 5' phosphate and the original 3'-hydroxyl terminus of the IVS. This recombination mechanism is analogous to that by which splicing of the precursor RNA is achieved. The circular molecules appear to have no direct function in RNA splicing, and we propose the cyclization serves to prevent unwanted RNA from driving the splicing reactions backwards.
TL;DR: In this paper, the authors discute des contraintes generales sur la variabilite impliquant l'efficacite de la conversion masse au repos-energie, the geometrie et les effets des paires.
Abstract: Les spectres des sources compactes qui rayonnent au-dessus de 511 keV peuvent etre modifies par les paires electron-positron crees par les collisions photon-photon. L'opacite Thomson due aux paires peut facilement depasser l'unite dans des sources comme les noyaux galactiques actifs. La coupure spectrale aux hautes energies est inversement reliee a la luminosite de la source. On discute des contraintes generales sur la variabilite impliquant l'efficacite de la conversion masse au repos-energie, la geometrie et les effets des paires. Les corrections relativistes peuvent etre grandes, meme dans une source isotrope
TL;DR: In this paper, a theoretical framework for the description of nonequilibrium solvation and solvent participation in the reaction coordinate for solution reactions is presented, illustrated by a model of reactive dipole isomerization.
Abstract: We construct a theoretical framework for the description of nonequilibrium solvation and solvent participation in the reaction coordinate for solution reactions. The framework is illustrated by a model of reactive dipole isomerization. We show that a multidimensional reaction coordinate picture is equivalent to a one dimensional description in which a generalized friction characterizes and quantifies nonequilibrium solvation effects on the reaction rate. The adiabatic regime where equilibrium solvation and mean potential ideas are correct is identified. Several distinct regimes of nonequilibrium solvation are identified and described in molecular terms. In the effective mass regime, equilibrium solvation ideas give the reaction barrier curvature correctly, but solvent inertia modifies the barrier passage rate. In the nonadiabatic regime, the solvent is ‘‘frozen’’ during the barrier passage and cannot provide equilibrium solvation. In the polarization caging regime, the reacting species adjust to the moving solvent, rather than vice versa, and the solvent is heavily involved in the reaction coordinate. The rate constant in each of these regimes is related to reactive and solvent dynamics.
TL;DR: In this article, the authors summarize the current understanding of the high-speed, bistable, threshold-sensitive electro-optic effects obtained in planar structures using surface interactions to suppress the spontaneous director helix characteristic of the bulk ferroelectric liquid crystal.
Abstract: The strong linear coupling of the director ň to electric field E in ferroelectric liquid crystals can be utilized to perform high-speed electro-optic switching suitable for device applications. In this article we summarize the current understanding of the high-speed, bistable, threshold-sensitive electro-optic effects obtained in planar structures using surface interactions to suppress the spontaneous director helix characteristic of the bulk ferroelectric liquid crystal.
TL;DR: It is concluded that phosphorylation of a population of the light-harvesting chlorophyll a/b protein complexes (LHC) in grana partitions causes the migration of these pigment proteins from the PS II-rich appressed membranes into the Photosystem I (PS I) enriched unstacked regions, which increases the absorptive cross section of PS I.
TL;DR: The interaction between phage R17 coat protein and its RNA binding site for translational repression was studied as an example of a sequence-specific RNA--protein interaction.
Abstract: The interaction between phage R17 coat protein and its RNA binding site for translational repression was studied as an example of a sequence-specific RNA--protein interaction. Nuclease protection and selection experiments define the binding site to about 20 contiguous nucleotides which form a hairpin. A nitrocellulose filter retention assay is used to show that the binding between the coat protein and a synthetic 21-nucleotide RNA fragment conforms to a simple bimolecular reaction. Unit stoichiometry and a Kd of about 1 nM are obtained at 2 degrees C in buffer containing 0.19 M salt. The interaction is highly sequence specific since a variety of RNAs failed to compete with the 21-nucleotide fragment for coat protein binding.