Showing papers by "University of Colorado Boulder published in 1982"
TL;DR: It is proposed that the IVS portion of the RNA has several enzyme-like properties that enable it to break and reform phosphodiester bonds and that enzymes, small nuclear RNAs and folding of the pre-rRNA into an RNP are unnecessary for these reactions.
2,077 citations
TL;DR: A beamforming structure is presented which can be used to implement a wide variety of linearly constrained adaptive array processors and is shown to incorporate algorithms which have been suggested previously for use in adaptive beamforming as well as to include new approaches.
Abstract: A beamforming structure is presented which can be used to implement a wide variety of linearly constrained adaptive array processors. The structure is designed for use with arrays which have been time-delay steered such that the desired signal of interest appears approximately in phase at the steered outputs. One major advantage of the new structure is the constraints can be implemented using simple hardware differencing amplifiers. The structure is shown to incorporate algorithms which have been suggested previously for use in adaptive beamforming as well as to include new approaches. It is also particularly useful for studying the effects of steering errors on array performance. Numerical examples illustrating the performance of the structure are presented.
1,923 citations
TL;DR: The Shine and Dalgarno sequence of 124 known gene beginnings is characterized and this information is used to make "rules" which help distinguish gene beginning from other sites in a library of over 78,000 bases of mRNA.
Abstract: We characterize the Shine and Dalgarno sequence of 124 known gene beginnings. This information is used to make "rules" which help distinguish gene beginning from other sites in a library of over 78,000 bases of mRNA. Gene beginnings are found to have information besides the initiation codon and Shine and Dalgarno sequence which can be used to make better "rules".
641 citations
TL;DR: The presentation proceeds from the derivation of the Gouy-Stodola theorem, the basis for entropy generation minimization in the conceptual design of heat transfer equipment, to suggest the minimum irreversibility design of one-dimensional insulations such as the main counterflow heat exchanger of a helium liquefaction plant.
Abstract: This review is devoted to the introduction of second-law analysis in heat transfer and entropy generation minimization in thermal design. The presentation proceeds from the derivation of the Gouy-Stodola theorem, the basis for entropy generation minimization in the conceptual design of heat transfer equipment. Appropriate analytical tools, such as the entropy generation number, are devised for the task of estimating the destruction of available work in the processes involving heat transfer. However, the entropy generation number concept is considerably more general, since it can be used to quantitatively describe the degree of irreversibility of engineering components and processes which do not draw their irreversibility solely from heat transfer. The examples considered in this article range from the irreversibility associated with some of the most fundamental convective heat transfer processes to the minimum irreversibility design of one-dimensional insulations such as the main counterflow heat exchanger of a helium liquefaction plant.
496 citations
TL;DR: The defined medium is highly selective for keratinocyte growth from a mixed inoculum of keratinocytes and fibroblasts, and very large colonies of flattened epithelial cells are obtained in the defined medium.
Abstract: Colony formation by normal human epidermal keratinocytes (HK) has been achieved in a medium that contains no deliberately added undefined supplements. The term "defined" is used to describe this medium, although the possibility that trace contaminants in its components could be contributing to the multiplication that it supports cannot yet be ruled out completely. The defined medium consists of a basal medium, MCDB 152, supplemented with 5 ng/ml epidermal growth factor (EGF), 10 micrograms/ml transferrin, 5 micrograms/ml insulin, 1.4 X 10(-6) M hydrocortisone, 1.0 X 10(-5) Methanolamine, 1.0 X 10(-5) M phosphoethanolamine, and 2.0 X 10(-9) M progesterone. MCDB 152 differs from MCDB 151, previously developed for multiplication of HK with small amounts of dialyzed serum (Peehl and Ham, 1980b), only by addition of the trace element mixture from human fibroblast medium MCDB 104 (McKeehan et al., 1977). Most of the requirement for transferrin, which is the least defined component of the defined medium, can be replaced by adding freshly dissolved and sterilized ferrous sulfate to the final medium after it has been filter sterilized. Insulin and EGF are clearly needed for optimal multiplication and hydrocortisone is mildly beneficial. Either ethanolamine or phosphoethanolamine must be present in the defined medium for HK multiplication. There is a greater need for EGF and less for hydrocortisone in the defined medium than in previous partially defined systems that we have worked with. Very large colonies of flattened epithelial cells are obtained in the defined medium, which has a low calcium concentration (0.03 mM) and does not favor keratinocyte differentiation. Less growth and more differentiation are obtained with higher calcium concentrations. The defined medium is highly selective for keratinocyte growth from a mixed inoculum of keratinocytes and fibroblasts.
446 citations
TL;DR: This chapter focuses on the important role of retrieval structures as working memory states, which contains structures for controlling the flow of processing within the current task and provides relatively fast and direct access to knowledge structures relevant to the currenttask and context.
Abstract: Publisher Summary This chapter focuses on the important role of retrieval structures as working memory states. The working memory has at least the following components: (1) short-term memory, which provides direct and virtually immediate access to very recent or attended knowledge states; (2) intermediate-term memory, the task-specific retrieval structure in long-term memory, which provides direct and relatively fast access to knowledge states; and (3) context, which contains structures for controlling the flow of processing within the current task and provides relatively fast and direct access to knowledge structures relevant to the current task and context. The auditory and visual–spatial buffers are important components of working memory.
424 citations
TL;DR: The theory of electron-cyclotron masers as they might apply in the astrophysical context is developed, and it is suggested that such masers provide an explanation for the very bright emission known to be associated with certain kinds of radio bursts observed on the Sun and other stars as discussed by the authors.
Abstract: The theory of electron-cyclotron masers as they might apply in the astrophysical context is developed, and it is suggested that such masers provide an explanation for the very bright emission known to be associated with certain kinds of radio bursts observed on the Sun and other stars. Some of the observed properties of solar and stellar radio bursts that seem to require amplification of the radiation are summarized, including millisecond solar spikes, RS CVn binaries, and flares on M dwarf stars. Recent developments in the theory of electron-cyclotron masers are summarized and the current theory is applied to electrons with a loss cone anisotropy, estimating the growth rate and saturation levels. In the interpretation of solar microwave spikes and RS CVn binaries, the mechanisms of gyromagnetic absorption, maser at the second harmonic, polarization, and angular distribution are examined in the light of the theory.
420 citations
TL;DR: This paper examined the effects of four aspects of student-faculty interaction (frequency of formal interaction, frequency of informal interaction, quality of faculty advising, and helpfulness of faculty) on a variety of student outcomes after four years.
Abstract: This study examined the effects of four aspects of student-faculty interaction (frequency of formal interaction, frequency of informal interaction, quality of faculty advising, and helpfulness of faculty) on a variety of student outcomes after four years. These effects were examined within a context of a causal model adapted from Astin's general college impact model. Outcomes data were gathered from a 1975 Freshman Questionnaire and a 1979 Graduating Students Survey. The results provided support for the importance of student-faculty interaction on the intellectual and personal/social outcomes of college and students' satisfaction with their educational experience.
384 citations
TL;DR: Like childhood cancer, adult cancer was found to be associated with high-current electrical wiring configurations (HCCs) near the patient's residence, which is consistent with a hypothesis of cancer promotion produced by AMF exposure.
Abstract: Like childhood cancer, adult cancer was found to be associated with high-current electrical wiring configurations (HCCs) near the patient's residence. Such wiring can expose occupants of the residence to alternating magnetic fields (AMFs) at a level which, though very low, may produce physiological effects. Several patterns in the data suggest that HCCs and cancer may be causally linked: (1) a dose-relationship was found. (2) The association did not appear to be an artefact of age, urbanicity, neighbourhood, or socioeconomic level. (3) The association was most clearly demonstrable where cancer caused by urban/industrial factors was least apt to obscure the effect. (4) A distinct pattern of latency between first exposure to the HCC and cancer diagnosis was seen, which is consistent with a hypothesis of cancer promotion produced by AMF exposure.
351 citations
TL;DR: Early region IA of human adenoviruses encodes a function required for normal induction of early viral genes and virus-induced cell transformation.
Abstract: Early region IA of human adenoviruses encodes a function required for normal induction of early viral genes and virus-induced cell transformation. The region is expressed at early times as two overlapping spliced mRNAs, 12S and 13S, which encode closely related proteins. To distinguish between the functions of these proteins, a single T → G transversion was constructed which prevents splicing of the 12S mRNA. This transversion, in the second base of the 12S mRNA intron, does not alter the protein encoded by the 13S mRNA due to degeneracy in the genetic code. Studies with this mutant demonstrated that only the 13S mRNA encodes the regulatory protein required for normal early gene expression.
290 citations
TL;DR: In this experiment, Italian and English adults were asked to interpret 81 simple sentences varying word order, animacy contrasts between the two nouns, topicalization and contrastive stress, and it is suggested that Italian is ‘less’ of an SVO language than English.
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TL;DR: The authors ranked economics departments according to the publication performance of affiliated faculty and made a contribution to the literature that ranks economics departments based on their publication performance in terms of the number of papers published by affiliated faculty.
Abstract: The paper has no abstract, but is an early contributor to the literature that ranks economics departments according to the publication performance of affiliated faculty Additional considerations are taken up
TL;DR: The recent progress in the detection of H2 in the interstellar medium is reviewed in this article, where the hydrogen molecule is discussed in terms of properties, and collisional excitation and dissociation rates.
Abstract: Recent progress in the detection of H2 in the interstellar medium is reviewed. The hydrogen molecule is discussed in terms of properties, and collisional excitation and dissociation rates. Molecular hydrogen formation and cooling and heating by H2 are also discussed. Ultraviolet studies provided information for the study of the formation-destruction equilibrium of H2, the kinetic temperature of the cloud, the hydrogen particle density, and the ultraviolet radiation field. Infrared observations in Orion and the planetary nebula NGC 7027 reveal two detections of vibrationally excited H2. In addition, thermal and nonthermal excitation mechanisms are discussed. Finally, it is noted that increased ultraviolet sensitivity is necessary for thorough H2 studies.
TL;DR: In this article, Jaffe and Reinhardt found substantial short time regularity even in the chaotic regions of phase space for what appears to be a large class of systems and attributed this regularity to remnants of destroyed invariant tori in phase space.
Abstract: Coupled nonlinear Hamiltonian systems are known to exhibit regular (quasiperiodic) and chaotic classical motions. In this and the preceding paper by Jaffe and Reinhardt, we find substantial short time regularity even in the chaotic regions of phase space for what appears to be a large class of systems. This regularity is demonstrated by the behavior of approximate constants of motion calculated by Pade summation of the Birkhoff–Gustavson normal form expansion and is attributed to remnants of destroyed invariant tori in phase space. The remnant toruslike manifold structures are used to suggest justification for use of Einstein–Brillouin–Keller semiclassical quantization procedures for obtaining quantum energy levels even in the absence of complete tori and to form a theoretical basis for the calculation of rate constants for intramolecular mode–mode energy transfer. These results are illustrated in a thorough analysis of the Henon–Heiles oscillator problem. Possible generality of the analysis is shown by b...
TL;DR: The structure of both bachelor's and master's level programs are described and courses are defined and the continuing need for education related to the definition, analysis, design, construction, and management of information systems in organizations is discussed.
Abstract: The recommendations of the 1972 and 1973 ACM Curriculum Committee on Information Systems programs have been influential in the development of degree programs at the bachelor's, master's, and doctoral levels The earlier curriculum has been revised and updated based on advances in the field over the past nine years The report discusses the continuing need for education related to the definition, analysis, design, construction, and management of information systems in organizations The structure of both bachelor's and master's level programs are described and courses are defined Course outlines include rationale for the courase, course objectives, instructional modes, and a list of topics Each topic is weighted in terms of suggested percent of time devoted to the subject
TL;DR: The Voyager 2 photopolarimeter was reprogrammed prior to the August 1981 Saturn encounter to perform orthogonal-polarization, two-color measurements on Saturn, Titan, and the rings, and multiple, very narrow strands of material were found in the Encke division and within the brightest single strand of the F ring.
Abstract: The Voyager 2 photopolarimeter was reprogrammed prior to the August 1981 Saturn encounter to perform orthogonal-polarization, two-color measurements on Saturn, Titan, and the rings. Saturn's atmosphere has ultraviolet limb brightening in the mid-latitudes and pronounced polar darkening north of 65 deg N. Titan's opaque atmosphere shows strong positive polarization at all phase angles (2.7 deg to 154 deg), and no single-size spherical particle model appears to fit the data. A single radial stellar occultation of the darkened, shadowed rings indicated a ring thickness of less than 200 meters at several locations and clear evidence for density waves caused by satellite resonances. Multiple, very narrow strands of material were found in the Encke division and within the brightest single strand of the F ring.
TL;DR: A survey of 164 recent purchasers of color television sets showed that consumer beliefs about the marketplace and about their capabilities as consumers accounted for 50% of the variance in extent of... as mentioned in this paper.
Abstract: A survey of 164 recent purchasers of color television sets shows that consumer beliefs about the marketplace and about their capabilities as consumers accounted for 50% of the variance in extent of...
TL;DR: In this paper, a comparison of results with those obtained using the conventional two-term spherical harmonic technique and using the Monte Carlo technique is made of electron energy distributions, transport coefficients, and excitation coefficients for electrons in a model atom valid in the case of low and high electron energies.
Abstract: The recently developed density gradient and multiterm spherical harmonic expansion technique for the numerical solution of the electron Boltzmann equation is evaluated by comparison of results with those obtained using the conventional two-term spherical harmonic technique and using the Monte Carlo technique. Comparisons are made of electron energy distributions, transport coefficients, and excitation coefficients for electrons in ${\mathrm{N}}_{2}$ at moderate electric-field to gas-density ratios $\frac{E}{N}$ where the large cross section for vibrational excitation leads to significant errors when conventional solutions of the Boltzmann equation are used. The $\frac{E}{N}$ values were varied from (1 - 200)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ V ${\mathrm{m}}^{2}$, corresponding to mean electron energies from 0.3 to 5 eV. The first two terms of the density-gradient expansion are used. As the number of terms $n$ in the spherical harmonic expansion is increased from the conventional two terms to $n\ensuremath{\ge}4$, the spherically symmetric component of the electron energy distribution and the transport and excitation coefficients become independent of $n$ and close to results obtained from the Monte Carlo calculation. The errors resulting from the use of two spherical harmonics at $\frac{E}{N}=7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}$ V ${\mathrm{m}}^{2}$, for example, are approximately 1, 5, and 30% for the drift velocity, the transverse diffusion coefficient, and the electronic excitation coefficients, respectively. For the lower $\frac{E}{N}$ values the errors in the transport coefficients are approximately proportional to an energy-loss-per-collision parameter. The variation of the coefficients of the lower-degree terms in the spherical-harmonic expansion with $n$ is examined through a comparison with an analytical solution of the Boltzmann equation for a model atom valid in the case of low $\frac{E}{N}$ and high electron energies. Monte Carlo techniques are used to show that the effects of electrodes are negligible for the conditions of recent measurements of electron excitation coefficients in ${\mathrm{N}}_{2}$.
TL;DR: The argument is presented that the coding performance of the triplet anticodon is enhanced by selection of a matching anticodon loop and stem sequence, which contains more coding information than the anticodon alone and can perform more efficiently and accurately at the ribosome.
Abstract: Transfer RNA's are probably very strongly selected for translational efficiency. In this article, the argument is presented that the coding performance of the triplet anticodon is enhanced by selection of a matching anticodon loop and stem sequence. the anticodon plus these nearby sequence features (the extended anticodon) therefore contains more coding information than the anticodon alone and can perform more efficiently and accurately at the ribosome. This idea successfully accounts for the relative efficiencies of many transfer RNA's.
TL;DR: In this article, a reduced integration method for solving incompressible flow problems "a la penalty" is critically examined vis-a-vis the consistent penalty method, and it is shown that the former method is only equivalent to the latter in certain special cases.
Abstract: SUMMARY The frequently used reduced integration method for solving incompressible flow problems 'a la penalty' is critically examined vis-a-vis the consistent penalty method. For the limited number of quadrilateral and hexahedral elements studied, it is shown that the former method is only equivalent to the latter in certain special cases. In the general case, the consistent penalty method is shown to be more accurate. Finally, we demonstrate significant advantages of a new element, employing biquadratic (2-D) or triquadratic (3-D) velocity and linear pressure over that using the same velocity but employing bilinear (2-D) or trilinear (3-D) pressure approximation.
TL;DR: In this article, the principle of global conservation of mass is used to define a unique direction for the outward pointing normal vector at any node on an irregular boundary of a domain containing an incompressible fluid.
Abstract: SUMMARY Various techniques for implementing normal and/or tangential boundary conditions in finite element codes are reviewed. The principle of global conservation of mass is used to define a unique direction for the outward pointing normal vector at any node on an irregular boundary of a domain containing an incompressible fluid. This information permits the consistent and unambiguous application of essential or natural boundary conditions (or any combination thereof) on the domain boundary regardless of boundary shape or orientation with respect to the co-ordinate directions in both two and three dimensions. Several numerical examples are presented which demonstrate the effectiveness of the recommended technique.
TL;DR: Light microscopy of the mitotic chromosomes of Caenorhabditis elegans suggests that non-localized kinetochores are present, since the chromosomes appear as stiff rods 1 to 2 μm in length and lack any visible constriction, and the holokinetic structure was confirmed by reconstructions of electron micrographs of dividing nuclei in serially sectioned embryos.
Abstract: Light microscopy of the mitotic chromosomes of Caenorhabditis elegans suggests that non-localized kinetochores are present, since the chromosomes appear as stiff rods 1 to 2 micrometers in length and lack any visible constriction. The holokinetic structure was confirmed by reconstructions of electron micrographs of dividing nuclei in serially sectioned embryos. In prophase the kinetochore appears as an amorphous projection approximately 0.18-0.2 micrometer in diameter in cross section and in longitudinal section it appears to be continuous along the chromatin. At prometaphase and metaphase the kinetochore is a convex plaque covering the poleward face of the chromosome and extending the length of the chromosome. In longitudinal section the kinetochore is a trilaminar structure with electron dense inner and outer layers of 0.02 micrometer, and an electron lucent middle layer of 0.03 micrometer. The inner layer is adjacent to a more electron dense region of chromatin. The kinetochore was also seen as a band extending the length of the chromosome in whole mount preparations of chromosomes stained with ethanolic phosphotungstic acid. Most gamma ray induced chromosome fragments segregate normally in embryonic mitoses, but some fragments display aberrant behavior. Similar behavior was seen in embryos carrying a genetically characterized free duplication. It is suggested that mitotic segregation of small fragments may be inefficient because the probability of attachment of microtubules to the kinetochore is proportional to kinetochore length.
TL;DR: The finding that some opioid-mediated forms of stress-induced analgesia are antagonized by hypophysectomy and dexamethasone has led to the suggestion that beta-endorphin, released from the pituitary, may mediate these analgesic reactions.
Abstract: The finding that some opioid-mediated forms of stress-induced analgesia are antagonized by hypophysectomy and dexamethasone has led to the suggestion that beta-endorphin, released from the pituitary, may mediate these analgesic reactions. "Long-term analgesia" (an opioid-mediated form of stress-induced analgesia), which is blocked by dexamethasone and hypophysectomy, was also blocked by adrenalectomy and reinstated with corticosterone therapy. Corticosterone is proposed to play a permissive role in long-term analgesia and to be a critical hormone mediating this phenomenon.
TL;DR: Optical density at 400 nm differs by about a factor of 22 between the average 1-month-old infant and the average 70-year-old adult.
Abstract: Scotopic spectral sensitivity was measured for nine observers (aged 4.5 months to 66 years) from 400 to 650 nm (10-nm steps) by using a 42 degree naturally viewed stimulus. The dependent measure was the visually evoked cortical-potential amplitude that was phase locked to an 8-Hz flickering stimulus. Sensitivity was similar for all observers at middle and long wavelengths, but at short wavelengths there was a decrease in sensitivity with increasing age. The density of the preretinal ocular media was estimated by subtracting the log scotopic spectral-sensitivity function of each observer from the human rhodopsin-absorbance spectrum when the two sets of curves were pinned at long wavelengths. The density of the infant ocular media was lower than that for adults. To quantify the sequence of ocular-media development, scotopic sensitivity was determined for an additional 42 observers (aged 1 month to 70 years) at two spectral points: 553 nm, where the optic-media density is low, and 405-430 nm, where the density is high. From these data, optic-media density at 400 nm was calculated. Despite substantial individual differences within each age, a clear aging function emerged. Preretinal optic-media density increased monotonically from birth throughout adulthood. Thus optical density at 400 nm differs by about a factor of 22 between the average 1-month-old infant and the average 70-year-old adult.
TL;DR: Shirts and Reinhardt as mentioned in this paper showed that the Henon-Heiles surface display sufficient regularity on a short to intermediate (but not long) time scale to allow use of standard EBK quantization techniques, taking advantage of the remnants of manifold structure.
Abstract: Qualitative arguments (made substantially more quantitative in the accompanying article by Shirts and Reinhardt) are put forward which indicate that the apparently chaotic dynamics on the Henon–Heiles surface display sufficient regularity on a short to intermediate (but not long) time scale to allow use of standard EBK quantization techniques, taking advantage of the remnants of manifold structure that these remarks imply. A complete uniform semiclassical quantization is carried out using the time independent technique of the Birkhoff–Gustavson normal form, recently introduced in the context of semiclassical quantization by Swimm and Delos.
TL;DR: Several collagen genes have been isolated from the nematode Caenorhabditis elegans and the complete nucleotide sequences of two of these genes, col-1 and col-2, have been determined.
01 Dec 1982-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: It is concluded that firing of the M-cell is causally related to the onset of C-type fast-start responses in adult fish, but, when the M -cell is inactivated, alternative neural pathways that coexist with theM-cell can initiate the C- type fast- start behavior pattern.
Abstract: 1.
Previous studies in adult fish show a one-to-one, time-locked, correlation between the presence of an initial action potential in the Mauthner (M-) cell and the onset of C-type fast-start responses in which the initial turn is away from the side of the active M-cell. In the present study we ask whether the M-cell is necessary for such behavioral acts.
2.
Single M-cells in goldfish were electrolytically lesioned by passing current (7.2 μA for 20 s) from a stainless steel microelectrode situated at the M-cell initial segment. Behavioral responses were elicited by dropping a ball into the aquarium holding the fish. The behavior was filmed at 500 frames/s and responses with an initial turn opposite the side of the lesioned cell (non-Mauthner responses) were compared with responses opposite the intact cell (M-initiated responses).
3.
Control experiments on acute preparations showed that such lesions prevent the M-cell from participating in behavioral responses because orthodromic synaptic activation of the M-axon is blocked, even though after the lesion the axon maintained resting potential and could conduct impulses to antidromic stimulation (Fig. 1). Chronic recordings from lesioned fish showed that in no case was the damaged M-cell observed to fire during any behavioral trials.
4.
The main finding was that non-Mauthner responses were no different in mechanical performance (angular velocity, displacement speed, etc.) or response probability than M-initiated responses (Figs. 4, 10, 11). The only difference was that the non-Mauthner responses were significantly longer in response latency than the M-initiated responses (Fig. 7). Such non-Mauthner responses have not yet been observed in intact goldfish.
5.
It is concluded that firing of the M-cell is causally related to the onset of C-type fast-start responses. But, when the M-cell is inactivated, alternative neural pathways that coexist with the M-cell can initiate the C-type fast-start behavior pattern.
TL;DR: Results of toxicity tests with several congeners of R -(+)-pulegone strongly implicated the α-isopropylidene ketone group as the structural unit required for eliciting hepatotoxicity, although the configurational orientation of the methyl group can modulate the hepatotoxic response.