Showing papers by "University of Colorado Boulder published in 1988"

The Multidimensional Scale of Perceived Social Support

Abstract: The development of a self-report measure of subjectively assessed social support, the Multidimensional Scale of Perceived Social Support (MSPSS), is described. Subjects included 136 female and 139 male university undergraduates. Three subscales, each addressing a different source of support, were identified and found to have strong factorial validity: (a) Family, (b) Friends, and (c) Significant Other. In addition, the research demonstrated that the MSPSS has good internal and test-retest reliability as well as moderate construct validity. As predicted, high levels of perceived social support were associated with low levels of depression and anxiety symptomatology as measured by the Hopkins Symptom Checklist. Gender differences with respect to the MSPSS are also presented. The value of the MSPSS as a research instrument is discussed, along with implications for future research.

Stability of protein structure and hydrophobic interaction.

Abstract: Publisher Summary This chapter focuses on the stability of protein structure and hydrophobic interaction The interest in hydrophobic interactions was stimulated by their unusual thermodynamic properties: it is believed that they are governed, not by enthalpic, but by entropic features, characterized by the undesirable entropy decrease of water in the vicinity of nonpolar groups The amount of polar groups in proteins is almost the same as the amount of nonpolar ones; and according to crystallographic studies, most of them are arranged at distances suggesting hydrogen bond formation Hydrogen bonds were invoked to various degrees of importance in explaining the stabilization of the native structure The chapter examines the main achievements of microcalorimetric studies of protein denaturation and of the dissolution of nonpolar substances in water The chapter also discusses calorimetric studies of protein denaturation The denaturational increment of the heat capacity can be partly explained by a gradual melting of the residual structure in the denatured protein on heating The large negative entropy of the transfer of a nonpolar substance to water at room temperature indicates a definite increase of the order in water in the presence of such solutes Of the two approaches to decomposing the thermodynamics for dissolution of nonpolar solutes into water, the first, from a reference point at the maximum of the free energy of transfer, leads to the concept of the compact state of the nonpolar substance

Against the Quantitative-Qualitative Incompatibility Thesis or Dogmas Die Hard

Abstract: Over approximately the last 20 years, the use of qualitative methods in educational research has evolved from being scoffed at to being viewed as useful for provisional exploration, to being accepted as a valuable alternative approach in its own right, to being embraced as capable of thoroughgoing integration with quantitative methods. Progress has been halting, and it is not surprising that certain thinkers are now balking at the latest stage of development. The chief worry is that the capitulation to "what works" ignores the incompatibility of the competing positivistic and interpretivist epistemological paradigms that purportedly undergird quantitative and qualitative methods, respectively. Appealing to a pragmatic philosophical perspective, this paper argues that no incompatibility between quantitative and qualitative methods exists at either the level of practice or that of epistemology and that there are thus no good reasons for educational researchers to fear forging ahead with "what works."

The discrete correlation function: a new method for analyzing unevenly sampled variability data

Abstract: A method for measuring correlation functions without interpolating in the temporal domain is proposed which provides an assumption-free representation of the correlation measured in the data and allows meaningful error estimates. Physical interpretation of the cross-correlation function of two series believed to be related by a convolution is shown to require knowledge of the input function's fluctuation power spectrum. Application of the method to two systems reveals no correlation for the optical data of Akn 120, but a strong correlation for the UV data of NGC 4151, placing bounds of between 1.2 and 20 light days on the size of the line-emitting region.

Directional mutation pressure and neutral molecular evolution.

Abstract: A quantitative theory of directional mutation pressure proposed in 1962 explained the wide variation of DNA base composition observed among different bacteria and its small heterogeneity within individual bacterial species. The theory was based on the assumption that the effect of mutation on a genome is not random but has a directionality toward higher or lower guanine-plus-cytosine content of DNA, and this pressure generates directional changes more in neutral parts of the genome than in functionally significant parts. Now that DNA sequence data are available, the theory allows the estimation of the extent of neutrality of directional mutation pressure against selection. Newly defined parameters were used in the analysis, and two apparently universal constants were discovered. Analysis of DNA sequence has revealed that practically all organisms are subject to directional mutation pressure. The theory also offers plausible explanations for the large heterogeneity in guanine-plus-cytosine content among different parts of the vertebrate genome.

Molecular tori in Seyfert galaxies - Feeding the monster and hiding it

Abstract: The principal properties of the tori of gas which surround Seyfert nuclei are discussed. The internal state of the clouds and their size distribution function are examined, and it is shown that the Jeans mass scale results in clouds which are individually sufficiently opaque to block out the nucleus, and that the balance of processes which controls their size distribution function also forces the covering factor to be of the order of or greater than unity. Where the gravitational potential is dominated by stars, cloud-cloud collisions keep the molecular clouds close to the equatorial plane. Stirring by stellar processes is never strong enough to compete with collisional losses. The position of the inner edge of the torus is determined by a balance between the inward flow of clouds and the rate at which the nuclear continuum can evaporate them.

Biochemical and physical characterization of an unmodified yeast phenylalanine transfer RNA transcribed in vitro.

Abstract: A recombinant plasmid was constructed with six synthetic DNA oligomers such that the DNA sequence corresponding to yeast tRNA(Phe) is flanked by a T7 promoter and a BstNI restriction site. Runoff transcription of the BstNI-digested plasmid with T7 RNA polymerase gives an unmodified tRNA of the expected sequence having correct 5' and 3' termini. This tRNA(Phe) transcript can be specifically aminoacylated by yeast phenylalanyl-tRNA synthetase and has a Km only 4-fold higher than that of the native yeast tRNA(Phe). The Km is independent of Mg2+ concentration, whereas the Vmax is very dependent on Mg2+ concentration. Comparison of the melting profiles of the native and the unmodified tRNA(Phe) at different Mg2+ concentrations suggests that the unmodified tRNA(Phe) has a less stable tertiary structure. Using one additional DNA oligomer, a mutant plasmid was constructed having a guanosine to thymidine change at position 20 in the tRNA gene. A decrease in Vmax/Km by a factor of 14 for aminoacylation of the mutant tRNA(Phe) transcript is observed.

The Impact Of Tourism Development On Residents' Perceptions Of Community Life

Abstract: Thepurpose of this study was to determine whether residents' perceptions of community life satisfaction vary with the levels of tourism development in theircommunity. Thestudy was conducted in 20 rural communities as part of the 1985 Colorado Rural Recreation Development Project administered by the University of Colorado-Boulder. A comprehen sive questionnaire investigating residents'perceptions of the importance of and their satis faction with seven dimensions of community life was distributed to one adult member of randomly selected households in each community. The seven dimensions ofcommunity life were public services, economics, environment, medical services, citizen involvement, for mal education, and recreation services. In order to determine which dimensions were most sensitive to changes in the level of tourism development, canonical analysis was conducted using tourism development ratings and community population as the set of independent variables and the seven importance and seven satisfaction...

Skeletonization: A Technique for Trimming the Fat from a Network via Relevance Assessment

Abstract: This paper proposes a means of using the knowledge in a network to determine the functionality or relevance of individual units, both for the purpose of understanding the network's behavior and improving its performance. The basic idea is to iteratively train the network to a certain performance criterion, compute a measure of relevance that identifies which input or hidden units are most critical to performance, and automatically trim the least relevant units. This skeletonization technique can be used to simplify networks by eliminating units that convey redundant information; to improve learning performance by first learning with spare hidden units and then trimming the unnecessary ones away, thereby constraining generalization; and to understand the behavior of networks in terms of minimal "rules."

Approximate solution of the trust region problem by minimization over two-dimensional subspaces

Abstract: The trust region problem, minimization of a quadratic function subject to a spherical trust region constraint, occurs in many optimization algorithms. In a previous paper, the authors introduced an inexpensive approximate solution technique for this problem that involves the solution of a two-dimensional trust region problem. They showed that using this approximation in an unconstrained optimization algorithm leads to the same theoretical global and local convergence properties as are obtained using the exact solution to the trust region problem. This paper reports computational results showing that the two-dimensional minimization approach gives nearly optimal reductions in then-dimension quadratic model over a wide range of test cases. We also show that there is very little difference, in efficiency and reliability, between using the approximate or exact trust region step in solving standard test problems for unconstrained optimization. These results may encourage the application of similar approximate trust region techniques in other contexts.

A study of influence in computer-mediated group decision making

Abstract: An emerging body of research in group decision support systems (GDSS) provides evidence that computer technology can and does impact the quality of decision making in groups. Most GDSS research is oriented toward examining the effects of a computer system on group outcomes, typically decision quality or group consensus, with the process itself often treated as a "black box." The research reported in this article addresses the need for a closer, micro-level examination of group process. An important group variable, namely influence behavior, was isolated and examined at various levels and by multiple methods. A model of specific GDSS effects on influence behavior was developed, based on an information exchange view of decision making and on the impact of a GDSS as a communication channel. Based on the research questions of interest in the study, several propositions and hypotheses were advanced and empirically tested on a specific implementation of a GDSS. Results were analyzed both quantitatively and qualitatively. The major empirical findings of the study showed no significant difference between the overall amount of influence behavior attempted in computer-supported versus unsupported groups, although significant differences were found in the pattern of influence behaviors, i.e., the different types of behaviors used. In addition, the distribution of influence behavior was more even in GDSS groups than in unsupported groups in one of two measures used. Empirical findings partially supported th research model, with indications that decision-making groups need more active guidance in understanding how to adapt computer support technology to their view of decision-making processes.

Chronic neurological sequelae of acute organophosphate pesticide poisoning

Abstract: To evaluate the latent neurological effects of organophosphate pesticide poisoning, this epidemiologic study examined 100 matched-pairs of individuals with previous acute organophosphate pesticide poisoning and nonpoisoned controls No significant difference between poisoned subjects and controls was found on audiometric tests, ophthalmic tests, electroencephalograms, or the clinical serum and blood chemistry evaluations Of the more than 50 scores from the neurological examination, abnormalities were demonstrated among the cases only on measures of memory, abstraction, and mood, and on one test of motor reflexes Differences between the two cohorts were much more apparent in the neuropsychological tests The differences occurred on tests of widely varying abilities including intellectual functioning, academic skills, abstraction and flexibility of thinking, and simple motor skills Twice as many cases as controls (24 vs 12) had Halstead-Reitan Battery summary scores in the range characteristic of individuals with cerebral damage or dysfunction Results from the Minnesota Multiphasic Personality Inventory and the Patient's and Relative's Assessment of Patient Functioning Inventories also revealed greater distress and complaints of disability for the poisoned subjects

CUUCGG hairpins: extraordinarily stable RNA secondary structures associated with various biochemical processes.

Abstract: The mRNA of bacteriophage T4 contains a strikingly abundant intercistronic hairpin. Within the 55 kilobases of known T4 sequence, the hexanucleotide sequence CTTCGG is found 13 times in the DNA strand equivalent to mRNA sequences. In 12 of those occurrences, the sequence is flanked by inverted repeats predictive of RNA hairpins with UUCG in the loop. Avian myeloblastosis virus reverse transcriptase, which can traverse hairpins of larger calculated stability, terminates efficiently at these CUUCGG hairpins. Thermal denaturation studies of model hairpins show that the loop sequence UUCG dramatically stabilizes RNA hairpins when compared to a control sequence. These data, when combined with previously described parameters of helix stability, suggest that T4 has utilized this loop sequence to optimize the stability of intercistronic hairpins. The stability of CUUCGG hairpins is also utilized in the RNAs of many organisms besides T4.

Phytoplankton nutrient limitation in Colorado mountain lakes

Abstract: SUMMARY. 1. Limiting nutrients for phytoplankton were studied experimentally in eight mountain lakes of central Colorado between May and November of 1984. 2. Five categories of phytoplankton limitation were identified: no limitation, N limitation, P limitation, concurrent limitation (stimulation only by simultaneous additions of N and P), and reciprocal limitation (stimulation by addition of either N or P). The phytoplankton communities of three lakes were primarily N-limited, one was primarily phosphorus-limited, and four showed primarily combined limitation (concurrent or reciprocal). Switching between categories of limitation was also observed within lakes. Nitrogen was the most frequently limiting nutrient; N, either alone or in combination with P, accounted for 79% of all observed instances of limitation. 3. Nine indices were tested for effectiveness in predicting phytoplankton limitation by N and P. The best indices for discriminating all limitations were ratios of dissolved inorganic N: total P (84% accuracy) and dissolved inorganic N:total dissolved P (80% accuracy). The effectiveness of these indices may be explained by the degree to which they represent N and P fractions actually available to the phytoplankton.

Development of tectonic cyclothems in rift, pull-apart, and foreland basins: Sedimentary response to episodic tectonism

Abstract: The thickest part of asymmetric rift, pull-apart, and foreland basin fills commonly consists of large-scale (hundreds to thousands of metres thick), tectonically generated cyclothems of fine-grained marine, lacustrine, or longitudinal fluvial deposits and coarse-grained transverse braid-plain or alluvial-fan deposits. The appearance of coarse clastics in these basin fills is typically noted as the time of tectonically rejuvenated source-area uplift, based on the conceptual tie between relief and coarse grain size, and on the application of the Davis theory of landform development. We propose the opposite interpretation: that the commencement of fine-grained sedimentation above coarse-grained deposits in a tectonic cyclothem is the best indicator of renewed tectonic activity. This reinterpretation is more consistent with (1) modern examples, (2) the consideration of source-area and sedimentary-basin geomorphology, (3) the disparity between the reaction rates of the various environments to subsidence, (4) the disparity between the rates of tectonic uplift and erosion, and (5) the controls on elastic-wedge progradation. In our model, extensive coarse-grained clastic-wedge progradation is an indicator of tectonically quiescent phases.

A Tsunami Deposit at the Cretaceous-Tertiary Boundary in Texas

Abstract: At sites near the Brazos River, Texas, an iridium anomaly and the paleontologic Cretaceous-Tertiary boundary directly overlie a sandstone bed in which coarse-grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple-laminated, very fine grained sandstone. This bed is the only sandstone bed in a sequence of uppermost Cretaceous to lowermost Paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths. Conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high. The most likely source for such a tsunami at the Cretaceous-Tertiary boundary is a bolidewater impact.

Toward Empirical Theory of Genocides and Politicides: Identification and Measurement of Cases since 1945

Abstract: This paper reports on a global survey of cases of massive state repression since World War II. The universe of analysis includes sustained episodes in which the state or its agents impose on a communal or political group “conditions of life calculated to bring about its physical destruction in whole or part.” We develop and use a typology which distinguishes between two categories of genocide (in which the victim groups are defined primarily in terms of communal characteristics) and four types of politicide (in which victim groups are defined in terms of their political status or opposition to the state). Forty-four episodes meet the operational guidelines developed here. Analysis of their properties and distribution shows that they occurred in all world regions, but with relatively few European and Latin American cases. Two or more began in each five-year period after 1945, with some clustering in the period of African decolonization; their median duration was five years. Aggregate fatalities were between seven and sixteen million people, at least as many who died in all international and civil wars in the period.

Multiple regression analysis of twin data: etiology of deviant scores versus individual differences.

Abstract: The multiple regression analysis of twin data in which a cotwin's score is predicted from a proband's score and the coefficient of relationship (the basic model) provides a statistically powerful test of genetic etiology. When an augmented model that also contains an interaction term is fitted to the same data set, direct estimates of heritability (h 2) and the proportion of variance due to shared environmental influences (c 2) are obtained. A simple transformation of selected twin data prior to regression analysis facilitates direct estimates of h 2 g (an index of the extent to which the difference between the mean of probands and that of the unselected population is heritable) and a test of the hypothesis that the etiology of deviant scores differs from that of variation within the normal range.

Nature and nurture during infancy and early childhood

Abstract: Preface Acknowledgments 1. Introduction 2. Individual differences and group differences 3. Quantitative genetics as the basis for a general theory of individual differences 4. The Colorado Adoption Project 5. Transitions and changes: description and prediction 6. Transitions and changes: genetic and environmental etiologies 7. Introduction to model fitting 8. Fitting sibling and parent-offspring models in the Colorado Adoption Project 9. Interactions 10. Genotype-environment correlation 11. Genetics and measures of the family environment: the nature of nurture 12. Conclusions References Author index Subject index.

X-ray sources in regions of star formation. III - Naked T Tauri stars associated with the Taurus-Auriga complex

Abstract: Ground-based and IRAS optical and IR spectroscopic and photometric observations are reported for 90 stars in or near 59 Einstein Observatory X-ray error circles in the Tau-Aur region. The data are presented in extensive tables and sample spectra and characterized in detail, with particular attention to 28 newly discovered 'naked' T Tau stars, which are shown to be normal stars with no significant IR or UV excess and ages of 1-40 Myr. These stars are found to outnumber normal T Tau stars by a factor of 10 in an area near the Tau-Aur dark clouds, and it is argued that their evolution toward the ZAMS is typical for low-mass stars. The implications of this finding for the time scales of circumstellar-disk dissipation and planet formation are discussed.

Foundations for the Arcadia environment architecture

Abstract: Early software environments have supported a narrow range of activities (programming environments) or else been restricted to a single “hard-wired” software development process. The Arcadia research project is investigating the construction of software environments that are tightly integrated, yet flexible and extensible enough to support experimentation with alternative software processes and tools. This has led us to view an environment as being composed of two distinct, cooperating parts. One is the variant part, consisting of process programs and the tools and objects used and defined by those programs. The other is the fixed part, or infrastructure, supporting creation, execution, and change to the constituents of the variant part. The major components of the infrastructure are a process programming language and interpreter, object management system, and user interface management system. Process programming facilitates precise definition and automated support of software development and maintenance activities. The object management system provides typing, relationships, persistence, distribution and concurrency control capabilities. The user interface management system mediates communication between human users and executing processes, providing pleasant and uniform access to all facilities of the environment. Research in each of these areas and the interaction among them is described.

Control of neuronal fate by the Drosophila segmentation gene even-skipped.

Abstract: The central nervous system (CNS) contains a remarkable diversity of cell types. The molecular basis for generating this neuronal diversity is poorly understood. Much is known, however, about the regulatory genes which control segmentation and segment identity during early Drosophila embryogenesis1,2. Interestingly, most of the segmentation and homoeotic genes in Drosophila, as well as many of their vertebrate homologues, are expressed during the development of the nervous system (for example, ref. 3). Are these genes involved in specifying the identity of individual neurons during neurogenesis, just as they specify the identity of cells during segmentation? We previously described the CNS expression of the segmentation gene fushi tarazu (ftz) and showed that ftz CNS expression is involved in the determination of an identified neuron3. Here we show that another segmentation gene, even-skipped (eve), is expressed in a different but overlapping subset of neurons. Temperature-sensitive inactivation of the eve protein during neurogenesis alters the fate of two of these neurons. Our results indicate that the nuclear protein products of the eve and ftz segmentation genes are components of the mechanism controlling cell fate during neuronal development.

The role of molecular hydrogen and methane oxidation in the water vapour budget of the stratosphere

Abstract: The detailed photochemistry of methane oxidation has been studied in a coupled chemical/dynamical model of the middle atmosphere The photochemistry of formaldehyde plays an important role in determining the production of water vapor from methane oxidation At high latitudes, the production and transport of molecular hydrogen is particularly important in determining the water vapor distribution It is shown that the ratio of the methane vertical gradient to the water vapor vertical gradient at any particular latitude should not be expected to be precisely 2, due both to photochemical and dynamical effects Modeled H2O profiles are compared with measurements from the Limb Infrared Monitor of the Stratosphere (LIMS) experiment at various latitudes Molecular hydrogen is shown to be responsible for the formation of a secondary maximum displayed by the model water vapor profiles in high latitude summer, a feature also found in the LIMS data