Showing papers by "University of Colorado Boulder published in 1994"

Characteristics of partnership success: Partnership attributes, communication behavior, and conflict resolution techniques

Abstract: The formation of partnerships between firms is becoming an increasingly common way for firms to find and maintain competitive advantage. While the antecedents of partnership formation and the characteristics of the resulting cooperative working relationship have been explored in the literature, an understanding of characteristics associated with partnership success is lacking. Such an understanding is important in reconciling the prescriptions to form partnerships with the reality that a majority of such partnerships do not succeed. We hypothesize that partnership attributes, communication behavior, and conflict resolution techniques are related to indicators of partnership success (satisfaction and sales volume in the relationship). The hypotheses are tested with vertical partnerships between manufacturers and dealers. Results indicate that the primary characteristics of partnership success are: partnership attributes of commitment, coordination, and trust; communication quality and participation; and the conflict resolution technique of joint problem solving. The findings offer insight into how to better manage these relationships to ensure success.

Theory of high-harmonic generation by low-frequency laser fields.

Abstract: We present a simple, analytic, and fully quantum theory of high-harmonic generation by low-frequency laser fields. The theory recovers the classical interpretation of Kulander et al. in Proceedings of the SILAP III Works hop, edited by B. Piraux (Plenum, New York, 1993) and Corkum [Phys. Rev. Lett. 71, 1994 (1993)] and clearly explains why the single-atom harmonic-generation spectra fall off at an energy approximately equal to the ionization energy plus about three times the oscillation energy of a free electron in the field. The theory is valid for arbitrary atomic potentials and can be generalized to describe laser fields of arbitrary ellipticity and spectrum. We discuss the role of atomic dipole matrix elements, electron rescattering processes, and of depletion of the ground state. We present the exact quantum-mechanical formula for the harmonic cutoff that differs from the phenomenological law Ip+3.17Up, where Ip is the atomic ionization potential and Up is the ponderomotive energy, due to the account for quantum tunneling and diffusion effects.

Transformation of mammalian cells by constitutively active MAP kinase kinase

Abstract: Mitogen-activated protein (MAP) kinase kinase (MAPKK) activates MAP kinase in a signal transduction pathway that mediates cellular responses to growth and differentiation factors. Oncogenes such as ras, src, raf, and mos have been proposed to transform cells by prolonging the activated state of MAPKK and of components downstream in the signaling pathway. To test this hypothesis, constitutively active MAPKK mutants were designed that had basal activities up to 400 times greater than that of the unphosphorylated wild-type kinase. Expression of these mutants in mammalian cells activated AP-1-regulated transcription. The cells formed transformed foci, grew efficiently in soft agar, and were highly tumorigenic in nude mice. These findings indicate that constitutive activation of MAPKK is sufficient to promote cell transformation.

Comptonization of Diffuse Ambient Radiation by a Relativistic Jet: The Source of Gamma Rays from Blazars?

Abstract: Recent Energy Gamma Ray Experiment Telescope (EGRET) observations of blazars have revealed strong, variable gamma-ray fluxes with no signatures of gamma-ray absorption by pair production. This radiation probably originates from the inner parts of relativistic jets which are aimed nearly toward us. On sub-parsec scales, the jet will be pervaded by radiation from the broad-line region, as well as by photons from the central continuum source (some of which will be scattered by thermal plasma). In a frame moving with the relativistic outflow, the energy of this ambient radiation would be enhanced. This radiation would be Comptonized by both cold and relativistic electrons in the jet, yielding (in the observer's frame) a collimated beam of X-rays and gamma rays. On the assumption that this process dominates self-Comptonization of synchrotron radiation, we develop a self-consistent model for variable gamma-ray emission, involving a single population of relativistic electrons accelerated by a disturbance in the jet. The spectral break between the X-ray and gamma-ray band, observed in 3C 279 and deduced for other blazars, results from inefficient radiative cooling of lower energy electrons. The existence of such a break strongly favors a model involving Comptonization of an external radiation field over a synchrotron self-Compton model. We derive constraints on such model parameters as the location and speed of the source, its dimensions and internal physical parameters, the maximum photon energies produced in the source, and the density and distribution of ambient radiation. Finally, we discuss how observations might discriminate between our model and alternative ones invoking Comptonization of ambient radiation.

Statehouse Democracy: Public Opinion and Policy in the American States

Abstract: The importance of public opinion in the determination of public policy is the subject of considerable debate. Whether discussion centres on local, state or national affairs, the influence of the opinions of ordinary citizens is often assumed yet rarely demonstrated. Other factors such as interest group lobbying, party politics and developmental, or environmental, constraints have been thought to have the greater influence over policy decisions. Professors Erikson, Wright and McIver make the argument that state policies are highly responsive to public opinion, and they show how the institutions of state politics work to achieve this high level of responsiveness. They analyse state policies from the 1930s to the present, drawing from, and contributing to, major lines of research on American politics. Their conclusions are applied to central questions of democratic theory and affirm the robust character of the state institution.

Matched subspace detectors

Abstract: We formulate a general class of problems for detecting subspace signals in subspace interference and broadband noise. We derive the generalized likelihood ratio (GLR) for each problem in the class. We then establish the invariances for the GLR and argue that these are the natural invariances for the problem. In each case, the GLR is a maximal invariant statistic, and the distribution of the maximal invariant statistic is monotone. This means that the GLR test (GLRT) is the uniformly most powerful invariant detector. We illustrate the utility of this finding by solving a number of problems for detecting subspace signals in subspace interference and broadband noise. In each case we give the distribution for the detector and compute performance curves. >

Costs, effects and C/E-ratios alongside a clinical trial

Abstract: A general approach is discussed to assess the uncertainty surrounding the cost effectiveness ratio (C/E-ratio) estimated on the basis of data from a randomised clinical trial. The approach includes the calculation of a 95% probability ellipse and introduces the concept of a so called C/E-acceptability curve. This last curve defines for each predefined C/E-ratio the probability that the C/E-ratio found in the study is acceptable. The approach is illustrated by estimates of costs per life saved and costs per patient discharged alive on the basis of data from a phase II trial addressing the value of anakinra in treating sepsis syndrome.

The Book of GENESIS: Exploring Realistic Neural Models with the GEneral NEural SImulation System

Abstract: This publication explains how to use the GENESIS simulation/modeling software system available through the Internet file-server at the California Institute of Technology, Pasadena, California, USA. The first part of the book consists of edited contributions from an international team of neural networks researchers working with GENESIS. They show the user the kind of models/simulations which can be created by using the software. The second part is a step-by-step tutorial for all professionals, researchers and students working in the area of neural networks and the cognitive sciences.

The Pricing of Initial Public Offerings: Tests of Adverse-Selection and Signaling Theories

Abstract: We test the empirical implications of several models of IPO underpricng. Consistent with the winner’s-curse hypothesis, we show that in markets where investors know a priori that they do not have to compete with informed investors, IPOs are not underpriced. We also show that IPOs underwritten by reputable investment banks experience significantly less underpricing and perform significantly better in the long run. We do not find empirical support for the signaling models that try to explain why firms underprice. In fact, we find that (1) firms that underprice more return to the reissue market less frequently, and for lesser amounts, than firms that underprice less, and (2) firms that underprice less experience higher earnings and pay higher dividends, contrary to the models’ predictions.

The Life Cycle of the Madden–Julian Oscillation

Abstract: A composite life cycle of the Madden-Julian oscillation (MJO) is constructed from the cross covariance between outgoing longwave radiation (OLR), wind, and temperature. To focus on the role of convection, the composite is based on episodes when a discrete signal in OLR is present. The composite convective anomaly possesses a predominantly zonal wavenumber 2 structure that is confined to the eastern hemisphere. There, it propagates eastward at about 5 m/s and evolves through a systematic cycle of amplification and decay. Unlike the convective anomaly, the circulation anomaly is not confined to the eastern hemisphere. The circulation anomaly displays characteristics of both a forced response, coupled to the convective anomaly as it propagates across the eastern hemisphere, and a radiating response, which propagates away from the convective anomaly into the western hemisphere at about 10 m/s. The forced response appears as a coupled Rossby-Kelvin wave while the radiating response displays predominantly Kelvin wave features. When it is amplifying, the convective anomaly is positively correlated to the temperature perturbation, which implies production of eddy available potential energy (EAPE). A similar correlation between upper-tropospheric divergence and temperature implies conversion of EAPE to eddy kinetic energy during this time. When it is decaying, temperature has shifted nearly into quadrature with convection, so their correlation and production of EAPE are then small. The same correspondence to the amplification and decay of the disturbance is mirrored in the phase relationship between surface convergence and anomalous convection. The correspondence of surface convergence to the amplification and decay of the convective anomaly suggests that frictional wave- Conditional Instability of the Second Kind (CISK) plays a key role in generating the MJO.

Precision measurement of strong field double ionization of helium

Abstract: The production of ${\mathrm{He}}^{+}$ and ${\mathrm{He}}^{2+}$ by a 160 fs, 780 nm laser has been measured over an unprecedented 12 orders of magnitude in counting range. Enhanced double electron emission, called nonsequential (NS) ionization, was observed over an intensity range where the single ionization dynamics is evolving from multiphoton to pure tunneling. The NS yield is found to scale with the ac-tunneling rate for the neutral, even when tunneling is not the dominant ionization pathway. A rescattering mechanism fails to predict the observed NS threshold or magnitude.

Representations of quasi-Newton matrices and their use in limited memory methods

Abstract: We derive compact representations of BFGS and symmetric rank-one matrices for optimization. These representations allow us to efficiently implement limited memory methods for large constrained optimization problems. In particular, we discuss how to compute projections of limited memory matrices onto subspaces. We also present a compact representation of the matrices generated by Broyden's update for solving systems of nonlinear equations.

Was There a ‘Medieval Warm Period’, and if so, Where and When?

Abstract: It has frequently been suggested that the period encompassing the ninth to the fourteenth centuries A.D. experienced a climate warmer than that prevailing around the turn of the twentieth century. This epoch has become known as the Medieval Warm Period, since it coincides with the Middle Ages in Europe. In this review a number of lines of evidence are considered, (including climate-sensitive tree rings, documentary sources, and montane glaciers) in order to evaluate whether it is reasonable to conclude that climate in medieval times was, indeed, warmer than the climate of more recent times. Our review indicates that for some areas of the globe (for example, Scandinavia, China, the Sierra Nevada in California, the Canadian Rockies and Tasmania), temperatures, particularly in summer, appear to have been higher during some parts of this period than those that were to prevail until the most recent decades of the twentieth century. These warmer regional episodes were not strongly synchronous. Evidence from other regions (for example, the Southeast United States, southern Europe along the Mediterranean, and parts of South America) indicates that the climate during that time was little different to that of later times, or that warming, if it occurred, was recorded at a later time than has been assumed. Taken together, the available evidence does not support a global Medieval Warm Period, although more support for such a phenomenon could be drawn from high-elevation records than from low-elevation records.

Estimating the mean and variance of the target probability distribution

Abstract: Introduces a method that estimates the mean and the variance of the probability distribution of the target as a function of the input, given an assumed target error-distribution model. Through the activation of an auxiliary output unit, this method provides a measure of the uncertainty of the usual network output for each input pattern. The authors derive the cost function and weight-update equations for the example of a Gaussian target error distribution, and demonstrate the feasibility of the network on a synthetic problem where the true input-dependent noise level is known. >

Head-direction cells in the rat posterior cortex. I. Anatomical distribution and behavioral modulation.

Abstract: We examined the behavioral modulation of head-directional information processing in neurons of the rat posterior cortices, including the medial prestriate (area Oc2M) and retrosplenial cortex (areas RSA and RSG). Single neurons were recorded in freely moving rats which were trained to perform a spatial working memory task on a radial-arm maze in a cue-controlled room. A dual-light-emitting diode (dual-LED) recording headstage, mounted on the animals' heads, was used to track head position and orientation. Planar modes of motion, such as turns, straight motion, and nonlocomotive states, were categorized using an objective scheme based upon the differential contributions of movement parameters, including linear and angular velocity of the head. Of 662 neurons recorded from the posterior cortices, 41 head-direction (HD) cells were identified based on the criterion of maintained directional bias in the absence of visual cues or in the dark. HD cells constituted 7 of 257 (2.7%) cells recorded in Oc2M, 26 of 311 (8.4%) cells in RSA, and 8 of 94 (8.5%) cells in RSG. Spatial tuning of HD cell firing was modulated by the animal's behaviors in some neurons. The behavioral modulation occurred either at the preferred direction or at all directions. Moreover, the behavioral selectivity was more robust for turns than straight motions, suggesting that the angular movements may significantly contribute to the head-directional processing. These behaviorally selective HD cells were observed most frequently in Oc2M (4/7, 57%), as only 5 of 26 (19%) of RSA cells and none of the RSG cells showed behavioral modulation. These data, taken together with the anatomical evidence for a cascade of projections from Oc2M to RSA and thence to RSG, suggest that there may be a simple association between movement and head-directionality that serves to transform the egocentric movement representation in the neocortex into an allocentric directional representation in the periallocortex.

Quantitative trait locus for reading disability on chromosome 6.

Abstract: Interval mapping of data from two independent samples of sibpairs, at least one member of whom was reading disabled, revealedevidence for a quantitative trait locus (QTL) on chromosome 6. Resultsobtained from analyses of reading performance from 114 sib pairsgenotyped for DNA markers localized the QTL to 6p21.3. Analyses ofcorresponding data from an independent sample of 50 dizygotic twinpairs provided evidence for linkage to the same region. Incombination, the replicate samples yielded a chi 2 value of 16.73 (P =0.0002). Examination of twin and kindred siblings with more extremedeficits in reading performance yielded even stronger evidence for aQTL (chi 2 = 27.35, P

Signal processing applications of oblique projection operators

Abstract: Oblique projection operators are used to project measurements onto a low-rank subspace along a direction that is oblique to the subspace. They may be used to enhance signals while nulling interferences. In the paper, the authors give several basic results for oblique projections, including formulas for constructing oblique projections with desired range and null space. They analyze the algebra and geometry of oblique projections in order to understand their properties. They then show how oblique projections can be used to separate signals from structured noise (such as impulse noise), damped or undamped interfering sinusoids (such as power line interference), and narrow-band noise. In some of the problems addressed, the oblique projection provides an alternative way to implement an already known solution. Expressing these solutions as oblique projections brings geometrical insight to the study of the solution. The geometry of oblique projections enables one to compute performance in terms of angles between signal and noise subspaces. As a special case of removing impulse noise, the authors can use oblique projections to interpolate missing data samples. In array processing, oblique projections can be used to simultaneously steer beams and nulls. In communications, oblique projections can be used to remove intersymbol interference. >

Meaningful Brands from Meaningless Differentiation: The Dependence on Irrelevant Attributes:

Abstract: Conventional product differentiation strategies prescribe distinguishing a product or brand from competitors’ on the basis of an attribute that is relevant, meaningful, and valuable to consumers. H...

The Impact of School Transitions in Early Adolescence on the Self-System and Perceived Social Context of Poor Urban Youth

Abstract: This study examined the effects of the normative school transition (n = 580) during early adolescence on the self-system and perceived school and peer social contexts of poor, black (n = 161), white (n = 146), and Latino (n = 273) youth in the public school systems of 3 eastern urban cities. The results revealed negative effects of the school transition on the affective and behavioral domains of the self-system. These declines in self-esteem, class preparation, and grade-point average (GPA) were common across race/ethnicity and gender. Concurrently, the school transition was perceived to be associated with changes in the school and peer contexts. Daily hassles with the school increased, while social support and extracurricular involvement decreased over the transition. Daily hassles with peers decreased, and peer values were perceived as more antisocial. These changes in the school and peer microsystems were also common across race/ethnicity and gender. In addition, transition-associated school and peer changes and, in particular, changes in daily hassles with the school were associated with changes in the academic dimensions of the self-system, that is, academic efficacy expectations, class preparation, and GPA. The results are discussed within a developmental mismatch framework.

FD-TD modeling of digital signal propagation in 3-D circuits with passive and active loads

Abstract: Most existing computer-aided circuit design tools are limited when digital clock speeds exceed several hundred MHz. These tools may not deal effectively with the physics of UHF and microwave electromagnetic wave energy transport along metal surfaces such as ground planes or in the air away from metal paths that are common at or above this frequency range. In this paper, we discuss full-wave modeling of electronic circuits in three dimensions using the finite-difference time-domain (FD-TD) solution of Maxwell's equations. Parameters such as stripline complex line impedance, propagation constant, capacitance per unit length and inductance per unit length can be easily computed as a function of frequency. We also discuss FD-TD Maxwell's equations computational modeling of lumped-circuit loads and sources in 3-D, including resistors and resistive voltage sources, capacitors, inductors, diodes, and transistors. We believe that this approach will be useful in simulating the large-signal behavior of very high-speed nonlinear analog and digital devices in the context of the full-wave time-dependent electromagnetic field. >

The Clementine Mission to the Moon: Scientific Overview

Abstract: In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

Molecular Tuning of Ion Binding to Calcium Signaling Proteins

Abstract: Intracellular calcium plays an essential role in the transduction of most hormonal, neuronal, visual, and muscle stimuli. (Recent reviews include Putney, 1993; Berridge, 1993a,b; Tsunoda, 1993; Gnegy, 1993; Bachs et al. 1992; Hanson & Schulman, 1992; Villereal & Byron, 1992; Premack & Gardner, 1992; Means et al. 1991).