Showing papers by "University of Notre Dame published in 1993"
TL;DR: In this article, a personal disposition toward proactive behavior, defined as the relatively stable tendency to effect environmental change, was investigated, and an initial scale to assess the construct and administered it to a sample of 282 undergraduates.
Abstract: This study investigated a personal disposition toward proactive behavior, defined as the relatively stable tendency to effect environmental change. We developed an initial scale to assess the construct and administered it to a sample of 282 undergraduates. Factor analysis led to a revised, unidimensional scale with sound psychometric properties. A second sample of 130 undergraduate students was used to determine the relationships between the proactive scale and the ’Big Five‘ personality domains: neuroticism, extraversion, openness, agreeableness, and conscientiousness. In a third sample of 148 MBA students, we assessed the proactive scale's relationships with three personality traits and three criterion measures. Consistent with hypotheses, scores on the proactive scale correlated with need for achievement, need for dominance, and independent measures of the nature of subjects' extracurricular and civic activities, the nature of their major personal achievements, and peer nominations of transformational leaders. We discuss the potential of the proactive construct to enhance our understanding of, and ability to predict, a wide range of behaviors.
2,412 citations
TL;DR: Progress in invasion studies hinges on realization that species' ranges are naturally dynamic; recognition that colonist species and target communities cannot be studied independently, but that species-community interactions determine invasion success.
Abstract: Anthropogenic introduction of species is homogenizing the earth's biota. Consequences of introductions are sometimes great, and are directly related to global climate change, biodiversity AND release of genetically engineered organisms. Progress in invasion studies hinges on the following research trends: realization that species' ranges are naturally dynamic; recognition that colonist species and target communities cannot be studied independently, but that species-community interactions determine invasion success; increasingly quantitative tests of how species and habitat characteristics relate to invasibility and impact; recognition from paleobiological, experimental and modeling studies that history, chance and determinism together shape community invasibility.
1,665 citations
TL;DR: In this article, a generalized Gaussian Markov random field (GGMRF) is proposed for image reconstruction in low-dosage transmission tomography, which satisfies several desirable analytical and computational properties for map estimation, including continuous dependence of the estimate on the data and invariance of the character of solutions to scaling of data.
Abstract: The authors present a Markov random field model which allows realistic edge modeling while providing stable maximum a posterior (MAP) solutions. The model, referred to as a generalized Gaussian Markov random field (GGMRF), is named for its similarity to the generalized Gaussian distribution used in robust detection and estimation. The model satisfies several desirable analytical and computational properties for map estimation, including continuous dependence of the estimate on the data, invariance of the character of solutions to scaling of data, and a solution which lies at the unique global minimum of the a posteriori log-likelihood function. The GGMRF is demonstrated to be useful for image reconstruction in low-dosage transmission tomography. >
978 citations
TL;DR: In this paper, the authors argue that for proper understanding of many processes of democratization, current conceptions of the state must be revised, especially with reference to its legal dimension, and several contrasts are drawn between representative, consolidated democracies and the democratic (i.e., polyarchical) forms that are emerging in most newly democratized countries, East and South.
940 citations
TL;DR: This paper argued that the combination of a multiparty system and a presidential system is more favorable for building stable democracies than a parliamentary system, starting from recent analyses that have argued that presidentialism is less favorable than parliamentary systems.
Abstract: Starting from recent analyses that have argued that presidentialism is less favorable for building stable democracy than parliamentary systems, this article argues that the combination of a multipa...
746 citations
TL;DR: It is shown that Bayesian segmentation using Gauss-Seidel iteration produces useful estimates at much lower signal-to-noise ratios than required for continuously valued reconstruction.
Abstract: A method for Bayesian reconstruction which relies on updates of single pixel values, rather than the entire image, at each iteration is presented. The technique is similar to Gauss-Seidel (GS) iteration for the solution of differential equations on finite grids. The computational cost per iteration of the GS approach is found to be approximately equal to that of gradient methods. For continuously valued images, GS is found to have significantly better convergence at modes representing high spatial frequencies. In addition, GS is well suited to segmentation when the image is constrained to be discretely valued. It is shown that Bayesian segmentation using GS iteration produces useful estimates at much lower signal-to-noise ratios than required for continuously valued reconstruction. The convergence properties of gradient ascent and GS for reconstruction from integral projections are analyzed, and simulations of both maximum-likelihood and maximum a posteriori cases are included. >
543 citations
TL;DR: This study shows for the first time that thermal hysteresis protein activity is also present in nonangiosperm plants, fungi, and bacteria, and identified for theFirst time in two additional kingdoms, the fungi and bacteria.
328 citations
Book•
02 Jan 1993TL;DR: Part 1 Theory and architectures: introduction to intelligent control systems with high degrees of autonomy, P.P. Passino and P.F. Stengel a framework for knowledge-based diagnosis in process operations, and design approaches and techniques: expert control.
Abstract: Part 1 Theory and architectures: introduction to intelligent control systems with high degrees of autonomy, P.A. Antsaklis and K.M. Passino a reference model architecture for intelligent systems design, J.S. Albus model-based architecture concepts for autonomous systems design and simulation, B.P. Zeigler and Sungdo Chi design of structure-based hierarchies for distributed intelligent control, L. Acar and U. Ozguner modelling and design of distributed intelligence systems, A.H. Levis nested hierarchical control, A. Meystel. Part 2 Design approaches and techniques: expert control, K.J. Astrom and K.-E. Arzen modelling and analysis of artificially intelligent planning systems, K.M. Passino and P.J. Antsaklis fuzzy and neural control, H.R. Berenji learning control systems, J.A. Farrell and W. Baker learning control methods, needs and architectures, M.M. Kokar learning in control, E. Grant. Part 3 Applications: intellingent robot prehension, Thang N. Nguyen and H. Stephanou modelling of multi-sensory robotic systems with failure diagnostic capabilities, K.P. Valavanis and G. Seetharaman AUTOCREW - a paradigm for intelligent flight control, B.L. Belkin and R.F. Stengel a framework for knowledge-based diagnosis in process operations, P.R. Prased and J.F. Davis.
307 citations
TL;DR: In this paper, the finite element method is applied to the solution of the transient Fokker-Planck equation for several often cited nonlinear stochastic systems accurately giving, for the first time, the joint probability density function of the response for a given initial distribution.
Abstract: The finite element method is applied to the solution of the transient Fokker-Planck equation for several often cited nonlinear stochastic systems accurately giving, for the first time, the joint probability density function of the response for a given initial distribution. The method accommodates nonlinearity in both stiffness and damping as well as both additive and multiplicative excitation, although only the former is considered herein. In contrast to the usual approach of directly solving the backward Kolmogorov equation, when appropriate boundary conditions are prescribed, the probability density function associated with the first passage problem can be directly obtained. Standard numerical methods are employed, and results are shown to be highly accurate. Several systems are examined, including linear, Duffing, and Van der Pol oscillators.
258 citations
01 Jan 1993
TL;DR: Hybrid control systems contain two distinct types of systems, continuous state and discrete-state, that interact with each other and their study is essential in designing sequential supervisory controllers for continuous-state systems.
Abstract: Hybrid control systems contain two distinct types of systems, continuous state and discrete-state, that interact with each other. Their study is essential in designing sequential supervisory controllers for continuous-state systems, and it is central in designing control systems with high degree of autonomy.
243 citations
TL;DR: In this article, a general theory of two-phase flow is proposed that is based on the basic principles of mass, momentum, and energy conservation and the second law of thermodynamics.
TL;DR: This study assesses genetic and environmental influences on the other three components of the five-factor model of personality: Openness to Experience, Agreeableness, and Conscientiousness.
Abstract: Previous research has indicated that extraversion and neuroticism are substantially affected both by genotype and environment. This study assesses genetic and environmental influences on the other three components of the five-factor model of personality: Openness to Experience, Agreeableness, and Conscientiousness. An abbreviated version of the NEO Personality Inventory (NEO-PI) was administered to 82 pairs of identical twins and 171 pairs of fraternal twins reared apart and 132 pairs of identical twins and 167 pairs of fraternal twins reared together. Estimates of genetic and environmental effects for Openness and Conscientiousness were similar to those found in other studies of personality: Genetic influence was substantial and there was little evidence of shared rearing environment. Results for Agreeableness were different: Genetic influence accounted for only 12% of the variance and shared rearing environment accounted for 21% of the variance. Few significant gender or age differences for genetic and environmental parameters were found in model-fitting analyses.
TL;DR: In this article, a method was proposed for the identification of the location of inflows-outflows in both creeks and streams, applied to a small creek in northern Indiana, involves measurement over time of both sediment temperature and the temperature at the base of the overlying water column.
TL;DR: Results indicated that social goal values were related to diverse aspects of self-reported negative adolescent outcomes, teacher-identified aggressive boys, and peer-reported social and behavioral functioning, and social goal choice had a clear relation to the social problem-solving differences of aggressive and nonaggressive boys.
Abstract: Examined the relations between adolescent boys' social goals of dominance, revenge, avoidance, and affiliation and (1) self-reported negative adolescent outcomes; (2) subjective sense of self-esteem; and (3) externalizing, internalizing, and prosocial behaviors, as rated by peers and teachers. Results indicated that social goal values were related to diverse aspects of self-, teacher-, and peer-reported social and behavioral functioning, with a consistent association found between a range of delinquent, substance-using, and behavioral difficulties, and endorsement of high goal values for dominance and revenge and low goal values for affiliation. Results also indicated that teacher-identified aggressive boys differed from nonaggressive boys in the value they placed on social goals, with aggressive boys placing a higher value on goals of dominance and revenge, and lower value on goals for affiliation. Finally social goal choice had a clear relation to the social problem-solving differences of aggressive and nonaggressive boys.
TL;DR: Results suggest that the rdgB protein, unlike the small soluble PI-TPs, is a membrane-associated PI- TP, which may be directly regulated by light-induced changes in intracellular calcium.
Abstract: The Drosophila retinal degeneration B (rdgB) mutation causes abnormal photoreceptor response and light-enhanced retinal degeneration. Immunoblots using polyclonal anti-rdgB serum showed that rdgB is a 160-kD membrane protein. The antiserum localized the rdgB protein in photoreceptors, antennae, and regions of the Drosophila brain, indicating that the rdgB protein functions in many sensory and neuronal cells. In photoreceptors, the protein localized adjacent to the rhabdomeres, in the vicinity of the subrhabdomeric cisternae. The rdgB protein's amino-terminal 281 residues are > 40% identical to the rat brain phosphatidylinositol transfer protein (PI-TP). A truncated rdgB protein, which contains only this amino-terminal domain, possesses a phosphatidylinositol transfer activity in vitro. The remaining 773 carboxyl terminal amino acids have additional functional domains. Nitrocellulose overlay experiments reveal that an acidic amino acid domain, adjacent to the PI transfer domain, binds 45Ca+2. Six hydrophobic segments are found in the middle of the putative translation product and likely function as membrane spanning domains. These results suggest that the rdgB protein, unlike the small soluble PI-TPs, is a membrane-associated PI-TP, which may be directly regulated by light-induced changes in intracellular calcium.
TL;DR: In this article, the authors studied wave evolution and selection on a vertically falling film and found that all finite-amplitude stationary waves with the same average thickness as the Nusselt flat film are constructed numerically from a boundary layer approximation of the equations of motion.
Abstract: Wave formation on a falling film is an intriguing hydrodynamic phenomenon involving transitions among a rich variety of spatial and temporal structures. Immediately beyond an inception region, short, near-sinusoidal capillary waves are observed. Further downstream, long, near-solitary waves with large tear-drop humps preceded by short, front-running capillary waves appear. Both kinds of waves evolve slowly downstream such that over about ten wavelengths, they resemble stationary waves which propagate at constant speeds and shapes. We exploit this quasi-steady property here to study wave evolution and selection on a vertically falling film. All finite-amplitude stationary waves with the same average thickness as the Nusselt flat film are constructed numerically from a boundary-layer approximation of the equations of motion. As is consistent with earlier near-critical analyses, two travelling wave families are found, each parameterized by the wavelength or the speed. One family γ1 travels slower than infinitesimally small waves of the same wavelength while the other family γ2 and its hybrids travel faster. Stability analyses of these waves involving three-dimensional disturbances of arbitrary wavelength indicate that there exists a unique nearly sinusoidal wave on the slow family γ1 with wavenumber αs (or α2) that has the lowest growth rate. This wave is slightly shorter than the fastest growing linear mode with wavenumber αm and approaches the wave on γ1 with the highest flow rate at low Reynolds numbers. On the fast γ2 family, however, multiple bands of near-solitary waves bounded below by αf are found to be stable to two-dimensional disturbances. This multiplicity of stable bands can be interpreted as a result of favourable interaction among solitary-wave-like coherent structures to form a periodic train. (All waves are unstable to three-dimensional disturbances with small growth rates.) The suggested selection mechanism is consistent with literature data and our numerical experiments that indicate waves slow down immediately beyond inception as they approach the short capillary wave with wavenumber α2 of the slow γ1 family. They then approach the long stable waves on the γ2 family further downstream and hence accelerate and develop into the unique solitary wave shapes, before they succumb to the slowly evolving transverse disturbances.
TL;DR: In this paper, the authors compared MANOVA and structural equation modeling (SEM) as alternative approaches to the detection of multivariate mean differences in between-groups designs and found that SEM provides an elegant alternative to MANOVA.
Abstract: Multivariate analysis of variance (MANOVA) and structural equation modeling (SEM) are compared as alternative approaches to the detection of multivariate mean differences in betweengroups designs MANOVA remains the most commonly implemented multivariate test of betweengroups mean differences When the set of outcome variables reflects a latent-variable system rather than an emergent-vari able system, however, SEM provides an elegant alternative to MANOVA Three generic types of latent-variab le systems were considered In the simplest case, SEM and MANOVA led to very similar substantive interpretations In the 2 more complex variable systems, SEM provided parameter estimates and collateral information that was at least as informative as those provided by MANOVA Researchers are encouraged to consider more carefully the nature of their variable systems before choosing too casually MANOVA over SEM
TL;DR: In this article, an in situ FTIR technique has been employed to probe the adsorption and photocatalytic degradation of 4-chlorophenol (4-CP) on TiO2 particles in a gas/solid system.
TL;DR: The equilibrium and dynamics of toluene adsorption and desorption in single component aqueous solutions were investigated in this article, where the dependence of the external mass-transfer coefficient on the hydrodynamic conditions in the liquid phase was taken into account.
Abstract: The equilibrium and dynamics of toluene adsorption and desorption in singlecomponent aqueous solutions were investigated. Adsorption rates in a batch reactor under a variety of operating conditions were fitted successfully with the homogeneous surface diffusion model and a surface diffusion coefficient that increases exponentially with surface concentration. The dependence of the external mass-transfer coefficient on the hydrodynamic conditions in the liquid phase was taken into account. Desorption studies in the aqueous phase and solvent regeneration of tolueneloaded activated carbon suggest that only a small fraction of toluene adsorbs irreversibly. Moreover, irreversible adsorption occurs only on virgin activated carbon, while adsorption on solvent-regenerated activated carbon is fully reversible. After accounting for irreversible adsorption, the model successfully predicted toluene desorption rates in the aqueous phase under various operating conditions using toluene transport parameters determined from the adsorption studies.
TL;DR: The I 2 molecule, which has been the subject of a great deal of femtosecond work, is studied theoretically as a prospect for experimental control and the optimal field indicates a simple underlying structure, in contrast with many previous fields obtained by optimal control theory.
TL;DR: Kinematically complete measurements for Coulomb dissociation of 2n into 2n were made at 28 MeV/nucleon in this paper, and the n-n correlation function suggests a large source size for the two-neutron emission.
Abstract: Kinematically complete measurements for Coulomb dissociation of $^{11}\mathrm{Li}$ into $^{9}\mathrm{Li}$+2n were made at 28 MeV/nucleon The n-n correlation function suggests a large source size for the two-neutron emission The electromagnetic excitation spectrum of $^{11}\mathrm{Li}$ has a peak, as anticipated in low-energy dipole resonance models, but a large post-breakup Coulomb acceleration of the $^{9}\mathrm{Li}$ fragment is observed, indicating a very short lifetime of the excited state and favoring direct breakup as the dissociation mechanism
TL;DR: Bivariate model-fitting analyses suggest that self-reported "irritable impulsiveness" and "(lack of) assertiveness/aggressiveness" show substantial, though different, genetic influences.
Abstract: The heritability of self-reported personality traits related to impulsiveness, irritability, and the inhibition of assertive or aggressive behavior was examined in up to 500 healthy monozygotic and dizygotic twin pairs raised together or apart. Two factors related to "(lack of) assertiveness/aggression" (Factor I) and "impulsive irritability" (Factor II) were examined using traditional and model-fitting procedures. Results of model-fitting procedures were consistent with a genetic, but not a shared environmental, influence for both factors. Further analysis suggested a nonadditive genetic influence for Factor II and an additive influence for Factor I. Bivariate model-fitting analyses suggest that self-reported "irritable impulsiveness" and "(lack of) assertiveness/aggressiveness" show substantial, though different, genetic influences.
TL;DR: In this article, the Coulomb dissociation of 28 MeV/nucleon into two neutrons by a Pb target was measured and a kinematically complete measurement was performed.
Abstract: We have performed a kinematically complete measurement of the Coulomb dissociation of 28 MeV/nucleon $^{11}\mathrm{Li}$ into $^{9}\mathrm{Li}$ and two neutrons by a Pb target. From the energies and angles of the emitted neutrons and of $^{9}\mathrm{Li}$, the excitation energy E of $^{11}\mathrm{Li}$ was determined on an event-by-event basis, and the Coulomb dissociation cross section as a function of excitation energy was constructed. The photonuclear cross section ${\mathrm{\ensuremath{\sigma}}}_{\mathit{E}1}$(E) and the dipole strength function dB(E1)/dE were determined from the Coulomb dissociation cross section. ${\mathrm{\ensuremath{\sigma}}}_{\mathit{E}1}$(E) has a peak at E=1.0 MeV and a width \ensuremath{\Gamma}=0.8 MeV. These parameters are consistent with the picture of a soft dipole mode. However, a significant post-breakup Coulomb acceleration of $^{9}\mathrm{Li}$ suggests instead a direct breakup. The complete kinematical measurement also allowed neutron and $^{9}\mathrm{Li}$ momentum distributions to be constructed in the rest frame of the $^{11}\mathrm{Li}$. The momentum distributions were fitted with Gaussian functions, yielding width parameters ${\mathrm{\ensuremath{\sigma}}}_{9}$=18\ifmmode\pm\else\textpm\fi{}4 MeV/c and ${\mathrm{\ensuremath{\sigma}}}_{\mathit{n}}$=13\ifmmode\pm\else\textpm\fi{}3 MeV/c. A more general feature of the breakup mechanism of $^{11}\mathrm{Li}$ could be deduced from these measurements. It was found that the $^{9}\mathrm{Li}$ and neutron momentum distributions and the neutron-neutron relative momentum distribution could be reproduced if the $^{11}\mathrm{Li}$ excitation energy was partitioned between the $^{9}\mathrm{Li}$ and the neutrons by a three-body phase space distribution. This indicates there is no directional correlation between the halo neutrons, and shows that the halo neutrons do not exist as a dineutron bound to a $^{9}\mathrm{Li}$ core.
TL;DR: This paper assessed three predictors of the assignment of credit and blame, self-handicapping, type of causal account, and performance outcome, and two consequences of such assignment: reward allocation and impressions of an actor.
Abstract: Assigning credit and blame to others for their successful and unsuccessful performances is a ubiquitous, yet relatively unstudied, process in organizations. Using a sample of 120 accountants, we assessed three predictors of the assignment of credit and blame—self-handicapping, type of causal account, and performance outcome—and two consequences of such assignment: reward allocation and impressions of an actor. Use of self-handicapping and external causal accounts diminished observers' assignments of blame for failure. In contrast, self-handicapping and causal accounts did not influence assignment of credit for success. Assignment of credit and blame significantly predicted reward allocation and impressions of the actor. We discuss implications for theory and practice and directions for future research.
TL;DR: A synthesis procedure for designing nonsymmetric cellular neural networks with a predetermined local interconnection structure that will store a set of desired bipolar vectors as memory points is presented.
Abstract: A synthesis procedure for designing nonsymmetric cellular neural networks (CNN) with a predetermined local interconnection structure that will store a set of desired bipolar vectors as memory points is presented. A specific case of constructing Chinese characters is presented to demonstrate the applicability of the results. Simulation results show that all the vectors corresponding to 50 commonly used Chinese characters are reachable memory vectors of the synthesized CNN. >
TL;DR: The use of second-order information in the coordination procedure results in improved convergence for nonhierarchic system optimization as compared with the authors' earlier studies using a first-order coordination procedure.
Abstract: An improved coordination procedure for the optimization of nonhierarchic systems by decomposition into reduced subspaces is presented. A subspace coordination procedure based on sequential global approximation is extended to include second-order information. This second-order global approximation is formed using information obtained during subspace optimizations. The use of second-order information in the coordination procedure results in improved convergence for nonhierarchic system optimization as compared with the authors' earlier studies using a first-order coordination procedure
TL;DR: Eigenfunctions and eigenvalues of the relativistic no-pair Hamiltonian are determined for low-[ital Z] ions, and the present calculations agree well with many-body perturbation theory and with the unified method, but disagree substantially with multiconfiguration Dirac-Fock (MCDF) calculations corrected for correlations.
Abstract: Eigenfunctions and eigenvalues of the relativistic no-pair Hamiltonian are determined for n=2 triplet states of heliumlike ions with charges in the range Z=5--100. The eigenfunctions are expanded in a basis of two-electron wave functions constructed from Dirac-Coulomb orbitals restricted to a finite cavity. The Hamiltonian matrix is evaluated and Davidson's method is then used to determine the lowest few eigenfunctions and eigenvalues. These calculations, which include the Coulomb interaction and the retarded Breit interaction, are corrected for QED and mass-polarization effects using values from Drake's unified method and are compared with other calculations and with experiment. For low-Z ions, the present calculations agree well with many-body perturbation theory and with the unified method, but disagree substantially with multiconfiguration Dirac-Fock (MCDF) calculations corrected for correlations. At Z=36, our term energies are lower than the unified method by \ensuremath{\lambda}${\mathrm{\ensuremath{\alpha}}}^{4}$${\mathit{Z}}^{4}$ a.u., where \ensuremath{\lambda}=0.033, 0.51, 0.16, and 0.003 for the 2 $^{3}$${\mathit{S}}_{1}$, 2 $^{3}$${\mathit{P}}_{0}$, 2 $^{3}$${\mathit{P}}_{1}$, and 2 $^{3}$${\mathit{P}}_{2}$ states, respectively. For Z=47 and 64, the present values of the 2 $^{3}$${\mathit{P}}_{0--}$2 $^{3}$${\mathit{P}}_{1}$ fine structure agree better with MCDF predictions than with the unified method. The energy intervals 2 $^{3}$${\mathit{P}}_{0}$-2 $^{3}$${\mathit{S}}_{1}$, 2 $^{3}$${\mathit{P}}_{1}$-2 $^{3}$${\mathit{S}}_{1}$, 2 $^{3}$${\mathit{P}}_{2}$-2 $^{3}$${\mathit{S}}_{1}$, and 2 $^{3}$${\mathit{P}}_{0}$-2 $^{3}$${\mathit{P}}_{1}$ are consistent with experiment throughout the entire range of Z.
Journal Article•
TL;DR: It is suggested that intervention with young mothers identified during pregnancy as having personal problems might forestall parenting problems that arise during early child rearing.
Abstract: This study examined "naturally occurring differences" in personal adjustment (social competence, behavior problems, and problem-solving skills) among representative groups of pregnant and nonpregnant adolescents and pregnant adults. Differences in parenting stress and parenting style were also assessed among a subsample of adolescent and adult mothers. Finally, the relationship between prenatally assessed personal adjustment and parenting was evaluated in the adolescent mother group. The contributions of important demographic characteristics (socioeconomic status and race) to both between- and within-group relationships were examined. Results suggested that pregnant adolescents were less socially competent and less proficient in their problem solving than their nonpregnant peers and that they exhibited more behavioral problems than a pregnant adult comparison group. Adolescent mothers displayed higher levels of parenting stress and were less responsive and sensitive in interactions with their infants than adult mothers. Support for the hypothesized link between prenatally assessed personal adjustment and adolescent parenting stress was found, whereas no relationship between socioeconomic status and race and parenting stress was established. These results suggest that intervention with young mothers identified during pregnancy as having personal problems might forestall parenting problems that arise during early child rearing. In recent years there has been concern about the increase in adolescent childbearing, especially in regard to the competence of teenage mothers to function effectively as sensitive and responsive parents. As a result of their asynchronous developmental transition, adolescent mothers are exposed to increased stress which may be detrimental to their well-being and that of their children (Feldman & Feldman, 1975; Russell, 1980; Ventura, 1980). Teenage mothers must cope not only with the stressors of adolescence, but also with stress associated with pregnancy and parenthood. These transactions occur at a time when their personal resources for coping with stress are still developing. Because of the multiple stressors they confront and their developmental immaturity, it has been argued that many adolescent mothers may provide less than optimal parenting to their children (Belsky, Lerner, & Spanier, 1984; Petersen & Crockett, 1986). A number of studies have noted significant differences between adults and adolescents in maternal affect and behaviors (Coll, Hoffman, & Oh, 1987; Jones, Green, & Krauss, 1980; Osofsky & Osofsky, 1970). Motherhood appears to be more stressful for adolescents than for adults (Brown, Adams, & Kellan, 1981; Thompson, 1982). Schilmoeller and Baranowski (1985) also found that adolescent mothers, compared to older mothers, were significantly less responsive to their children, less stimulating, and more restrictive and punitive. Other research has indicated that adolescent mothers were less likely to verbally interact with their infants (Brooks-Gunn & Furstenberg, 1986; Epstein, 1980; McLaughlin, Sandler, Sherrod, Vietze, & O'Conner, 1979; Osofsky & Osofsky, 1970; Roosa, Fitzgerald, & Carlson, 1982). Heinicke, Diskin, Ramsey-Klee, and Given (1983) suggested that problematic interactional patterns between the adolescent mother and her infant can be best understood through an examination of the mother's stable personal characteristics. Based on both theory and research, it seems particularly likely that a major determinant of parenting effectiveness is the mother's general personal adjustment (Lazarus, 1976; Tyler, 1978). A mother who is socially and psychologically well adjusted should be better prepared to deal with the numerous stressors associated with raising a child and more effective in her parenting interactions. Support for this assumption has been found in several studies. Colletta and Gregg (1981) reported that the level of emotional stress experienced by adolescent mothers was less for those with greater personal resources and more direct coping styles. …
TL;DR: Compared growth and mortality of individually maintained crayfish offered one of five ad libitum diets: invertebrates, macrophytes, dentritus, periphyton or all items combined, O. rusticus grew more quickly and/or was better able to survive overall than its congeners and O. virilis grew more than O. propinquus.
Abstract: We are exploring mechanisms of an invasion that contradicts the oft-cited generalization that species invade vacant niches. In northern Wisconsin lakes, the introduced crayfish Orconectes rusticus is replacing two ecologically similar resident congeners, O. virilis and O. propinquus. In laboratory experiments, we compared growth and mortality of individually maintained crayfish offered one of five ad libitum diets: invertebrates, macrophytes, dentritus, periphyton or all items combined. Mortality was highest for O. virilis and lowest for O. rusticus. Macrophyte diets yielded the highest mortality. All three species grew best on invertebrate and combination diets but grew little or not at all on diets of periphyton, detritus or macrophytes. O. rusticus and O. virilis grew more than O. propinquus. O. rusticus grew more quickly and/or was better able to survive overall than its congeners. Therefore, O. rusticus would probably have advantages over O. virilis and O. propinquus in competitive interactions, reproductive success and avoiding size-selective fish predation. Subtle interspecific differences may interact strongly with other ecological factors and contribute to the displacement of resident species from a well-occupied niche.
27 Apr 1993
TL;DR: The problem of image decompression is cast as an ill-posed inverse problem, and a stochastic regularization technique is used to form a well-posed reconstruction algorithm which produces reconstructed images which greatly reduced the noticeable artifacts which exist using standard techniques.
Abstract: The problem of image decompression is cast as an ill-posed inverse problem, and a stochastic regularization technique is used to form a well-posed reconstruction algorithm. A statistical model for the image which incorporates the convex Huber minimax function is proposed. The use of the Huber minimax function rho T(.) helps to maintain the discontinuities from the original image which produces high-resolution edge boundaries. Since rho T(.) is convex, the resulting multidimensional minimization problem is a constrained convex optimization problem. The maximum a posteriori (MAP) estimation technique that is proposed results in the constrained optimization of a convex functional. The proposed image decompression algorithm produces reconstructed images which greatly reduced the noticeable artifacts which exist using standard techniques. >