Showing papers by "University of Nebraska–Lincoln published in 1994"

Emotion regulation: a theme in search of definition

Abstract: Contemporary interest in emotion regulation promises to advance important new views of emotional development as well as offering applications to developmental psychopathology, but these potential contributions are contingent on developmentalists' attention to some basic definitional issues. This essay offers a perspective on these issues by considering how emotion regulation should be defined, the various components of the management of emotion, how emotion regulation strategies fit into the dynamics of social interaction, and how individual differences in emotion regulation should be conceptualized and measured. In the end, it seems clear that emotion regulation is a conceptual rubric for a remarkable range of developmental processes, each of which may have its own catalysts and control processes. Likewise, individual differences in emotion regulation skills likely have multifaceted origins and are also related in complex ways to the person's emotional goals and the immediate demands of the situation. Assessment approaches that focus on the dynamics of emotion are well suited to elucidating these complex developmental and individual differences. In sum, a challenging research agenda awaits those who enter this promising field of study.

Measuring phenological variability from satellite imagery

Abstract: Vegetation phenological phenomena are closely related to seasonal dynamics of the lower atmosphere and are therefore important elements in global models and vegetation monitoring. Normalized difference vegetation index (NDVI) data derived from the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiom- eter (AVHRR) satellite sensor offer a means of efficiently and objectively evaluating phenological characteristics over large areas. Twelve metrics linked to key phenological events were computed based on time-series NDVI data collected from 1989 to 1992 over the conterminous United States. These measures include the onset of greenness, time of peak NDVI, maximum NDVI, rate of greenup, rate of senescence, and integrated NDVI. Measures of central tendency and variabil- ity of the measures were computed and analyzed for various land cover types. Results from the analysis showed strong coincidence between the satellite-derived metrics and pre- dicted phenological characteristics. In particular, the metrics identified interannual variability of spring wheat in North Dakota, characterized the phenology of four types of grasslands, and established the phenological consistency of deciduous and coniferous forests. These results have implications for large- area land cover mapping and monitoring. The utility of re- motely sensed data as input to vegetation mapping is demon- strated by showing the distinct phenology of several land cover types. More stable information contained in ancillary data should be incorporated into the mapping process, particu- larly in areas with high phenological variability. In a regional or global monitoring system, an increase in variability in a region may serve as a signal to perform more detailed land cover analysis with higher resolution imagery.

The Relationship Between Efficacy and the Instructional Practices of Special Education Teachers and Consultants

Abstract: ABSIRACT:The relationship between efficacy and selected instructional vareables was explored for two types of special education teachers. Teachers were categorized either as direct service providers, who provided direct instruction or behavioral interventions to students with mild disabilities, or as indirect service providers, who spent at least 50% of their time consulting, collaborating, or team teaching with general educators. Significant positive correlations found between efficacy and three instructionally-relevant factors were for both types of teachers. Type of service was related to only one instructional component, Instructional Experimentation. Recommendations for teacher education are addressed.

Binary-encounter-dipole model for electron-impact ionization

Abstract: A theoretical model, which is free of adjustable or fitted parameters, for calculating electron-impact ionization cross sections for atoms and molecules is presented. This model combines the binary-encounter theory with the dipole interaction of the Bethe theory for fast incident electrons. The ratios of the contributions from distant and close collisions and interference between the direct and exchange terms are determined by using the asymptotic behaviors predicted by the Bethe theory for ionization and for stopping cross sections. Our model prescribes procedures to calculate the singly differential cross section (energy distribution) for each subshell using the binding energy, average kinetic energy, and the differential dipole oscillator strengths for that subshell. Then the singly differential cross section is integrated over the ejected electron energy to obtain the total ionization cross section. The resulting total ionization cross section near the threshold is proportional to the excess energy of the projectile electron. We found that this model yields total ionization cross sections for a variety of atoms and molecules from threshold to several keV which are in good agreement (\ensuremath{\sim}10% or better on average) with known experimental results. The energy distributions also exhibit the expected shapes and magnitudes. We offer a simpler version of the model that can be used when differential oscillator strengths are not known. For the ionization of ions with an open-shell configuration, we found that a minor modification of our theory greatly improves agreement with experiment.

The role of acid phosphatases in plant phosphorus metabolism

Abstract: Hydrolysis of phosphate esters is a critical process in the energy metabolism and metabolic regulation of plant ceils. This review summarizes the characteristics and putative roles of piant acid phosphatase lAPasel. Although immunologicaliy closely related, plant APases display remarkable heterogeneity w ith regards to their kinetic and molecular properties, and subcellular location. The secreted APa.ses of roots and cell cultures are relati\ ely non-specific enzymes that appear to be important in the hydrolysis and mobilization of P, from extracellular phosphomonoesters for plant nutrition. Intracelluiar APases are undoubtedly involved in the routine utilization of P, reserves or other P, containing compounds. A special class of intracellular APase exists that demonstrate a clear-cut (but generally nonabsoiute) substrate selectivity. These .^.Pases are hypothesized to have distinct metabolic functions and include; phytase, phosphoglycoiate phosphatase. 3-pbosphoglycerate phosphatase. phosphoenolpyruvate phosphatase. and phosphotyrosyl-protein phosphatase. APase expression is regulated by a variety of developmental and environmental factors. P, starvation induces de novo synthesis of extra- and intracellular APases in cell cultures as well as in whole plants. Recommendations are made to achieve uniformity in the analyses of the different .A.Pase isoforms normally encountered within and between different plant tissues.

The GLABRA2 gene encodes a homeo domain protein required for normal trichome development in Arabidopsis.

Abstract: The GLABRA2 gene (GL2) is one of several genes known to have a role in trichome development in Arabidopsis. Mutations at this locus result in abnormal trichome expansion. We have identified several gl2 mutants from a T-DNA-mutagenized population of plants. The T-DNA insert in one of the mutant lines cosegregated with the recessive gl2 phenotype and thus served as a molecular tag to isolate genomic DNA at the putative GL2 locus. RFLP analysis of the segregating population and subsequent molecular complementation experiments established that the GL2 gene had been cloned. The predicted polypeptide from one of the ORFs contained on this fragment showed significant identity to the homeo domain sequence. The construction of a full-length cDNA by RT-PCR confirmed the presence of a homeo box in the GL2 gene and showed that it is substantially different from other recently cloned homeo box genes in plants. The expression pattern of GL2, as demonstrated by in situ hybridization, indicated that the gene is expressed in trichome progenitor cells and at stages associated with trichome development. This suggests that GL2 may regulate events required for the directional cell expansion observed during trichome formation.

Poverty, Social Support, and Parental Behavior

Abstract: The associations among poverty, measures of social support, and parents' reports of punitive and unsupportive behaviors were examined using the National Survey of Families and Households. Analyses revealed a significant interaction between perceived social support and household income: perceived social support was negatively associated with parents' reports of punitive behavior, but mainly when income was low. The amount of help received from others was negatively associated with parents' reports of unsupportive behavior. The study suggests that some forms of social support lower levels of problematic behavior among all parents, whereas other forms of social support are particularly beneficial to parents living in poverty.

Universal hashing and authentication codes

Abstract: In this paper, we study the application of universal hashing to the construction of unconditionally secure authentication codes without secrecy. This idea is most useful when the number of authenticators is exponentially small compared to the number of possible source states (plaintext messages). We formally define some new classes of hash functions and then prove some new bounds and give some general constructions for these classes of hash functions. Then we discuss the implications to authentication codes.

Light Reflectance Compared with Other Nitrogen Stress Measurements in Corn Leaves

Abstract: New tools that can rapidly quantify the N status of corn could be valuable in N fertilizer management practices. This study was conducted to compare light reflectance from corn leaves with other parameters used to detect N deficiencies. Light reflectance (400-700 nm) as measured from corn leaves in the laboratory with a Hunter tristimulus colorimeter was compared with Minolta SPAD 502 chlorophyll meter readings (light transmittance at 650 and 940 nm), leaf N concentrations, and specific leaf N (N content per unit area). Measurements were made on individual ear leaves collected from an irrigated corn N response trial with four hybrids and have N treatments. Light reflectance near 550 nm was the best wavelength to separate N treatment differences. Reflectance at 550 nm provided a stronger relationship with both leaf N concentration and chlorophyll meter reading than between chlorophyll meter readings and leaf N concentration. The measurement of light reflectance near 550 nm has promise as a technique to detect N deficiencies in corn leaves

Gravity models: a reformulation and an application to discriminatory trade arrangements

Abstract: Gravity Models are used to estimate trade flows from 162 countries into 11 major importing countries for 1976, counting the EC as one. The main theories underlying gravity models are reviewed and a new gravity model is derived from a linear expenditure system. A major innovation of this model is that both tariffs and dummy variables for discriminatory arrangements are incorporated. Price variables are also explicitly included in the model. The tariff and the dummy variables are found to be statistically significant and this indicates that previous gravity model studies which used dummies to estimate the trade benefits of preferential tariffs may not have accurately estimated the effects of the preferences. The price variables generally are also found to be statistically significant, which casts doubt on the homogeneous-goods assumption underlying the purchasing power parity hypothesis. Some significant differences in the estimates were found when separate equations were regressed for the EEC and the US.

Wet corn distillers byproducts compared with dried corn distillers grains with solubles as a source of protein and energy for ruminants.

Abstract: Five trials investigated the feeding value of wet and dried corn distillers byproducts as a source of protein and energy for growing and finishing cattle and investigated the effect of heat damage on the feeding value of dried distillers byproducts. In a calf growth trial, no differences in rate of gain or protein efficiency were observed among calves fed wet distillers byproducts (wet distillers grains + thin stillage; WDB) or one of three composites of dried distillers grains + solubles (DDGS) having a low, medium, or high concentration of ADIN. A finishing trial compared the energy value of dry-rolled corn (DRC) with WDB or the three DDGS composites, fed at 40% of the diet DM replacing DRC. Cattle consuming WDB or DDGS gained faster ( P .lo). In a lamb finishing trial, the addition of 5 or 10% ethanol did not affect (P > .lo) daily gain, DMI, or feed efficiency. In two metabolism trials with steers, grain byproducts (wet distillers grains, dry distillers grains plus solubles, wet corn gluten feed, dry corn gluten feed, hominy feed) and DRC had similar effects on ruminal pH and total VFA. Feeding thin stillage or condensed solubles reduced (P < .lo) ruminal pH and tended to reduce acetate:propionate. Wet corn distillers byproducts, fed at 40% of the diet DM, contain more NE, than did DRC and drying WDB reduces its NE, content. Acid detergent insoluble N is a poor indicator of protein and energy value in distillers grains.

Structural aspects of face recognition and the other-race effect.

Abstract: The other-race effect was examined in a series of experiments and simulations that looked at the relationships among observer ratings of typicality, familiarity, attractiveness, memorability, and the performance variables ofd’ and criterion. Experiment 1 replicated the other-race effect with our Caucasian and Japanese stimuli for both Caucasian and Asian observers. In Experiment 2, we collected ratings from Caucasian observers on the faces used in the recognition task. A Varimax-rotated principal components analysis on the rating and performance data for the Caucasian faces replicated Vokey and Read’s (1992) finding that typicality is composed of two orthogonal components, dissociable via their independent relationships to: (1) attractiveness and familiarity ratings and (2) memorahility ratings. For Japanese faces, however, we fond that typicality was related only to memorahility. Where performance measures were concerned, two additional principal components dominated by criterion and byd’ emerged for Caucasian faces. For the Japanese faces, however, the performance measures ofd’ and criterion merged into a single component that represented a second component of typicality, one orthogonal to thememorability-dominated component. A measure offace representation quality extracted from an autoassociative neural network trained with a majority of Caucasian faces and a minority of Japanese faces was incorporated into the principal components analysis. For both Caucasian and Japanese faces, the neural network measure related both to memorability ratings and to human accuracy measures. Combined, the human data and simulation results indicate that the memorahility component of typicality may be related to small, local, distinctive features, whereas the attractiveness/familiarity component may be more related to the global, shape-based properties of the face.

Incorporation of helium, neon, argon, krypton, and xenon into fullerenes using high pressure

Abstract: To investigate the spectroscopic and other properties of these interesting noble gas compounds, it is necessary to increase the fraction of fullerene molecules occupied. We have done this by carrying out the incorporation step at high pressures of the gas. Part-per-million levels of the noble gases produce no measurable effects in the conventional mass spectrum, since the peaks due to ions containing these atoms are well below the noise level. However, samples of fullerene heated in the presence of Ne (38,000 psi, 66% recovery), Ar (40,000 psi, 45% recovery), Kr (24,500 psi, 25% recovery), and Xe (18,000 psi, 45% recovery) show distinct and reproducible peaks (electron impact ionization) for fullerene ions containing the noble gases. The theoretical mass spectra of the corresponding adducts were calculated using the natural isotopic abundance of the involved atoms. Agreement between calculated and experimental curves provides convincing evidence that Ne C[sub 60], Ar C[sub 60], Kr C[sub 60], Xe C[sub 60], Ne C[sub 70], Ar C[sub 70], Kr C[sub 70], and Xe C[sub 70] have been synthesized. 18 refs., 2 figs.

Contact with Nonresident Parents, Interparental Conflict, and Children's Behavior

Abstract: Previous studies have yielded inconsistent results about the implications of contact with nonresidential parents for children in single-parent households. This study tested the hypothesis that children's contact with nonresident parents decreases children's behavior problems when interparental conflict is low but increases children's behavior problems when interparental conflict is high. Data were analyzed from 1,285 children in single-parent families from the National Survey of Families and Households. The hypothesis was supported among boys from divorced families. No support for the hypothesis was found among girls, regardless of family background.

Research in Collegiate Mathematics Education. I

Abstract: The chapter sketches some of the landscape of current research in undergraduate mathematics education and offers useful information for present and future faculty members. Six research projects related to the teaching and learning of post-secondary mathematics are summarized. Approaches in the research reported here include individual interviews, classroom observations, national survey, and in-depth study of a particular instance or case of learning. The collegiate mathematics topics at the heart of the respective studies range from calculus, combinatorics, linear algebra, and foundations of proof to the application of mathematics to teaching in the development of future teachers.

Procedural justice explanations and employee reactions to economic hardship: A field experiment

Abstract: In a randomized field experiment involving 173 salaried employees, treatment subjects received an explanation for an ongoing pay freeze. This explained the fairness of the decision process leading to the freeze and the fairness of the implementation of the freeze. The explanation mitigated the effect of the resultant economic hardship on employee attitudes, turnover intentions, and perceptions of procedural justice

Life-Span Adjustment of Children to Their Parents' Divorce

Abstract: Children who experience parental divorce, compared with children in intact two-parent families, exhibit more conduct problems, more symptoms of psychological maladjustment, lower academic achievement, more social difficulties, and poorer self-concepts. Similarly, adults who experienced parental divorce as children, compared with adults raised in continuously intact two-parent families, score lower on a variety of indicators of psychological, interpersonal, and socioeconomic well-being. However, the overall group differences between offspring from divorced and intact families are small, with considerable diversity existing in children's reactions to divorce. Children's adjustment to divorce depends on several factors, including the amount and quality of contact with noncustodial parents, the custodial parents' psychological adjustment and parenting skills, the level of interparental conflict that precedes and follows divorce, the degree of economic hardship to which children are exposed, and the number of stressful life events that accompany and follow divorce. These factors can be used as guides to assess the probable impact of various legal and therapeutic interventions to improve the well-being of children of divorce.

Eicosanoids mediate insect nodulation responses to bacterial infections.

Abstract: We propose that nodule formation is mediated by eicosanoids in insects. Nodulation is the temporally and quantitatively predominant cellular defense response to bacterial infection in insects and other invertebrates. Inhibition of eicosanoid biosynthesis in larvae of the tobacco hornworm Manduca sexta immediately prior to intrahemocoelic infections with the bacterium Serratia marcescens strongly reduced the nodulation response. Inhibition of eicosanoid biosynthesis also reduced formation of cellular aggregates at 1 hr postinfection, which indicates that eicosanoids mediate early stages of nodulation. Separate treatments with specific inhibitors of phospholipase A2, cyclooxygenase, and lipoxygenase reduced nodulation, which supports the view that nodule formation is a complex process involving prostaglandins and lipoxygenase products. The inhibitory effects of the phospholipase A2 inhibitor dexamethasone on nodulation were apparent by 1 hr after infection, and the effects increased, relative to controls, over 24 hr. The dexamethasone effects were expressed in a dose-dependent manner, and they were reversed by treating infected insects with eicosanoid-precursor polyunsaturated fatty acids. Treatments with the saturated fatty acid 16:0, which is not an eicosanoid precursor, did not reverse the dexamethasone effects on nodulation. These findings strongly support the identification of nodulation as a specific insect cellular defense mechanism that is mediated by eicosanoids.

Chiral Separation Mechanisms in Protein-Based HPLC Columns. 2. Kinetic Studies of (R)- and (S)-Warfarin Binding to Immobilized Human Serum Albumin

Abstract: This work used plate height measurements to investigate the kinetics of (R)- and (S)-warfarin binding to an immobilized HSA column. The dissociation rate constants for (R)- and (S)-warfarin on this column increased from 0.06 to 1.9 s-1 and from 0.06 to 0.36 s-1 between 4 and 45 °C. The corresponding association rate constants increased from 2.4 × 104 to 3.2 × 105 M-1 s-1 for (R)-warfarin and from 4.4 × 104 to 7.2 × 104 M-1 s-1 for (S)-warfarin over the same temperature range. From the dissociation data, it was found that an increase in temperature led to a large decrease in the plate height due to stationary phase mass transfer for both enantiomers. Further studies indicated that (R)- and (S)-warfarin had similar activation energies for their binding to HSA. For (R)-warfarin, most of this energy requirement was due to the change in enthalpy of the system, while for (S)-warfarin, it was mainly due to the change in entropy. All of these results agree with an earlier model, in which (R)- and (S)-warfarin wer...

Mobilization Processes and the 1989 Chinese Democracy Movement

Abstract: Using a multimethod strategy, we identify and analyze mobilization processes associated with the rapid emergence of the 1989 Chinese Democracy Movement. We propose that the confluence of macro-, me...

Increased virulence of a human enterovirus (coxsackievirus B3) in selenium-deficient mice

Abstract: Coxsackievirus B3 (CVB3/20)-induced myocarditic lesions occurred more quickly and were more severe and virus titers in heart and liver were higher in selenium (Se)-deficient than Se-adequate mice. NK cell activity and serum neutralizing antibody titers were similar in both Se-adequate and -deficient CVB3/20-infected mice; however, lymphocyte proliferation to both mitogen and antigen was decreased in Se-deficient mice. CVB3/20 isolated from Se-deficient donor mice and inoculated into Se-adequate recipient mice induced severe myocarditis. In contrast, CVB3/20 isolated from Se-adequate donor mice and inoculated into Se-adequate recipient mice induced only moderate myocarditis, similar to that caused by the original virus stock. Thus, the general population of CVB3/20 virions, as a consequence of replicating in an Se-deficient host, underwent a phenotypic change to increased virulence. These results have important implications for the emergence of virulent viruses.

Techniques for monitoring crop nitrogen status in corn

Abstract: Nitrogen (N) fertilizers used in corn production contribute to the occurrence of nitrate to ground water. Tissue testing is a tool that can aid in fertilizer N management. Several tissue testing techniques were evaluated for their potential to aid in N management of irrigated corn in Nebraska. Leaf N content provided a traditional means of identifying N deficiencies in corn. Leaf N concentrations were difficult to interpret because of luxury consumption and the lack of consistent critical levels across hybrids and growth stages. Chlorophyll meters showed little sensitivity to luxury consumption and provided instantaneous results, but required an in‐field reference fertilized with extra N. Chlorophyll meter readings were highly correlated with grain yield and provided early detection of a N deficiency. The combination of chlorophyll meter data and irrigation demonstrated the merits of a “fertilization‐as‐needed”; approach to N management. The post‐harvest stalk nitrate test accurately identified s...

Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. 5: Variability of the ultraviolet continuum and emission lines of NGC 3783

Abstract: We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or 'dips,' the first lasting is less than or approximately 20 days and the second is less than or approximately 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became 'harder' when brighter. The variations in the continuum occurred simultaneously at all wavelengths (delta(t) is less than 2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Ly(alpha), the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or 'lag.' As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of (formally) approximately 0 days for He II + O III), and approximately 4 days for Ly(alpha) and C IV. The data further suggest lags of approximately 4 days for Si IV + O IV) and 8-30 days for Si III + C III). Mg II lagged the 1460 A continuum by approximately 9 days, although this result depends on the method of measuring the line flux and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over timescales of is less than or approximately 2 days, and that the character of the continuum variability may change with time.