Showing papers by "University of Virginia published in 1992"

Network Dyads in Entrepreneurial Settings: A Study of the Governance of Exchange Relationships

Abstract: Investigates network dyads and the manner in which control is exercised in these structures. Four entrepreneurial, high growth firms, each from a different industry, were selected to participate in this ethnographic analysis. The represented industries are telephone equipment, clothing, computer hardware, and environmental support systems. Seven network dyads were identified for the four firms considered. The partnerships were typically other members of the value chain - e.g., suppliers, distributors and final customers. The analysis identified three phases for the network dyad development: preconditions for exchange, conditions to build, and integration and control. The first phase, preconditions, utilized prior relations in addition to personal and firm reputations to reduce uncertainty and establish expectations and obligation. The second phase, the building process, has significant reliance on the trust and the development of reciprocity norms. The third phase is marked by three forms of integration: operational, strategic, and social control. Examination of the four firms and their seven dyadic relationships support the model. These firms were found to be engaged in stable, sustained relationships with a high degree of cooperation and collaboration. The mode of exchange found in these dyadic relationships is characterized as a network form of governance, which appears to be beneficial to high growth firms. Further research using this model could be done for R&D partnerships, cooperative marketing agreements, and other forms of strategic alliances and joint ventures. (SRD)

Tectonic forcing of late Cenozoic climate

Abstract: Global cooling in the Cenozoic, which led to the growth of large continental ice sheets in both hemispheres, may have been caused by the uplift of the Tibetan plateau and the positive feedbacks initiated by this event. In particular, tectonically driven increases in chemical weathering may have resulted in a decrease of atmospheric C02 concentration over the past 40 Myr.

A practical and theoretical guide to measurement invariance in aging research

Abstract: We describe mathematical and statistical models for factor invariance. We demonstrate that factor invariance is a condition of measurement invariance. In any study of change (as over age) measurement invariance is necessary for valid inference and interpretation. Two important forms of factorial invariance are distinguished: "configural" and "metric". Tests for factorial invariance and the range of tests from strong to weak are illustrated with multiple group factor and structural equation modeling analyses (with programs such as LISREL, COSAN, and RAM). The tests are for models of the organization and age changes of intellectual abilities. The models are derived from current theory of fluid (Gf) and crystallized (Gc) abilities. The models are made manifest with measurements of the WAIS-R in the standardization sample. Although this is a methodological paper, the key issues and major principles and conclusions are presented in basic English, devoid of technical details and obscure notation. Conceptual principles of multivariate methods of data analysis are presented in terms of substantive issues of importance for the science of the psychology of aging.

pp125FAK a structurally distinctive protein-tyrosine kinase associated with focal adhesions.

Abstract: Expression of the Rous sarcoma virus-encoded oncoprotein, pp60v-src, subverts the normal regulation of cell growth, which results in oncogenic transformation. This process requires the intrinsic protein-tyrosine kinase activity of pp60v-src and is associated with an increase in tyrosine phosphorylation of a number of cellular proteins, candidate substrates for pp60v-src. We report here the isolation of a cDNA encoding a protein, pp125, that is a major phosphotyrosine-containing protein in untransformed chicken embryo cells and exhibits an increase in phosphotyrosine in pp60v-src-transformed chicken embryo cells. This cDNA encodes a cytoplasmic protein-tyrosine kinase which, based upon its predicted amino acid sequence and structure, is the prototype for an additional family of protein-tyrosine kinases. Immunofluorescence localization experiments show that pp125 is localized to focal adhesions; hence, we suggest the name focal adhesion kinase.

Characterization of peptides bound to the class I MHC molecule HLA-A2.1 by mass spectrometry

Abstract: Antigens recognized by T cells are expressed as peptides bound to major histocompatibility complex (MHC) molecules. Microcapillary high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry was used to fractionate and sequence subpicomolar amounts of peptides isolated from the MHC molecule HLA-A2.1. Of 200 different species quantitated, eight were sequenced and four were found in cellular proteins. All were nine residues long and shared a distinct structural motif. The sensitivity and speed of this approach should enhance the analysis of peptides from small quantities of virally infected and transformed cells as well as those associated with autoimmune disease states.

The determinants of parenting behavior.

Abstract: Explored factors that influence parenting behavior through examination of previously reported and more recently developed models for predicting parenting behavior. Patterson's behavioral model, Abidin's initial model of parenting stress, and Belsky's process model of determinants of parenting are reviewed. A proposed model is presented to improve on previous models by integrating sociological, environmental, and behavioral factors, as well as personality characteristics of the parent, in predicting parenting behavior. Finally, description is provided on a new self-report measure (i.e., the Parenting Alliance Inventory) developed to focus on those aspects of the marital relationship that bear directly on parenting. Implications for future research are presented.

Developmental theories for the 1990s: development and individual differences.

Abstract: Understanding both typical human development and indivdual differences within the same theoretical framework has been difficult because the 2 orientations arise from different philosophical traditions. It is argued that an evolutionary perspective can unite the study of both species-typical development and individual variation. Research on determininants of development from many perspectives can be understood within an evolutionary framework in which organism and environment combine to produce development. Species-normal genes and environments and indidividual variations in genes and environments both affect personality, social, and intellectual development. These domains are used as examples to integrate theories of normal development and individual differences. Within the usual samples of European, North American, and developed Asian countries, the results of family and twin studies show that environments within the normal species range are crucial to normal development. Given a wide range of environmental opportunities and emotional supports, however, most children in these societies grow up to be individually different based on their individual genotypes. Understanding the ways in which genes and environments work together helps developmentalists to identify children in need of intervention and to tailor interventions to their particular needs.

Overview no. 96: Evolution of F.C.C. deformation structures in polyslip

Abstract: The microstructural evolution during polyslip in f.c.c. metals in investigated by the examples of Al, Ni, NiCo alloys and an AlMg alloy, deformed at room temperature either by rolling or by torsion. The principles governing this evolution appears to be the following: (a) There are differences in the number and selection of simultaneously acting slip systems among neighboring volume elements of individual grains. In any one volume element (called a cell block), the number of slip systems falls short of that required for homogeneous (Taylor) deformation, but groups of neighboring cell blocks fulfil the Taylor criterion collectively. (b) The dislocations are trapped into low-energy dislocation structures in which neigboring dislocations mutually screen their stresses. The microstructural evolution at small strains progresses by the subdivision of grains into cell blocks delineated by dislocation boundaries. These boundaries accomodate the lattice misorientations, which result from glide on different slip system combinations in neighbouring cell blocks. The cell blocks are subdivided into ordinary cells and both cell blocks and cells shrink with increasing strain. All observations appear to be in good accord with the theoretical interpretation. However, some problems remain to be solved quantitatively.

Assessing Distress in Pediatric Intensive Care Environments: The COMFORT Scale

Abstract: Managing psychological distress is a central treatment goal in Pediatric Intensive Care Units (PICUs), with medical and psychological implications. However, there is no objective measure for assessing efficacy of pharmacologic and psychological interventions used to reduce distress. Development of the COMFORT scale is described, a nonintrusive measure for assessing distress in PICU patients. Eight dimensions were selected based upon a literature review and survey of PICU nurses. Interrater agreement and internal consistency were high. Criterion validity, assessed by comparison with concurrent global ratings of PICU nurses, was also high. Principal components analysis revealed 2 correlated factors, behavioral and physiologic, accounting for 84% of variance. An ecological-developmental model is presented for further study of children's distress and coping in the PICU.

Saharan dust in the Amazon Basin

Abstract: Saharan dust is shown to enter the Central Amazon Basin (CAB) in bursts which accompany major wet season rain systems. Low-level horizontal convergence feeding these rain systems draws dust from plumes which have crossed the tropical Atlantic under the large-scale circulation fields. Mass exchange of air between the surface and 4 km over the eastern Amazon basin is calculated using rawinsonde data collected during storm events. Mean concentrations of dust observed by aircraft over the western tropical Atlantic are used to calculate the amount of dust injected into the Basin. Individual storm events inject some 480,000 tons of dust into the north-eastern Amazon Basin. Storm and dust climatology suggest that the annual importation of dust is in the order of 13 Mtons. In the north-eastern basin, this may amount to as much as 190 kg ha -1 yr -1 . Deposition of trace species, such as phosphate, associated with this dust ranges from 1-4 kg ha -1 yr -1 . Uncertainties in these estimates are not believed to be greater than ± 50% and may be as low as ± 20%. The deposition fluxes from Saharan dust are essentially identical to the CAB wet deposition fluxes from precipitation in the wet season; a result that implies that the major ionic composition of rain water in the CAB wet season may be strongly influenced by inputs of material originating on the African continent nearly 5000 km away. The total amount of Saharan dust calculated to enter the Amazon basin is 1/2 to 1/3 of that estimated to cross 60°W longitude between 10° and 25°N latitude. We conclude that part of the productivity of the Amazon rain forest is dependent upon critical trace elements contained in the soil dust originating in the Sahara/Sahel. This dependence should be reflected by expansions and contractions of the Amazon rain forest in direct relationship to expansions and contractions of the Sahara/Sahel. Turnover rates for nutrient species deposited with Saharan dust in the Amazon Basin suggest a time scale of 500 to 20,000 years. We believe the dependence of one large ecosystem upon another separated by an ocean and coupled by the atmosphere to be fundamentally important to any view of how the global system functions. Any strategy designed to preserve the Amazonian rain forest or any part thereof should equally concern itself with the inter-relationship between the rain forest, global climate and arid zones well removed from Amazonia. DOI: 10.1034/j.1600-0889.1992.t01-1-00005.x

Peptides presented to the immune system by the murine class II major histocompatibility complex molecule I-Ad

Abstract: Between 650 and 2000 different peptides are associated with the major histocompatibility complex class II molecule I-Ad. Sequences for nine of these were obtained by a combination of automated Edman degradation and tandem mass spectrometry. All of the peptides are derived from secretory or integral membrane proteins that are synthesized by the antigen-presenting cell itself. Peptides were 16 to 18 residues long, had ragged NH2-and COOH-termini, and contained a six-residue binding motif that was variably placed within the peptide chain. Binding data on truncated peptides suggest that the peptide binding groove on class II molecules can be open at both ends.

Activation of mitogen-activated protein kinase kinase by v-Raf in NIH 3T3 cells and in vitro

Abstract: Mitogen-activated protein (MAP) kinases are 42- and 44-kD serine-threonine protein kinases that are activated by tyrosine and threonine phosphorylation in cells stimulated with mitogens and growth factors. MAP kinase and the protein kinase that activates it (MAP kinase kinase) were constitutively activated in NIH 3T3 cells infected with viruses containing either of two oncogenic forms (p35EC12, p3722W) of the c-Raf-1 protein kinase. The v-Raf proteins purified from cells infected with EC12 or 22W viruses activated MAP kinase kinase from skeletal muscle in vitro. Furthermore, a bacterially expressed v-Raf fusion protein (glutathione S-transferase-p3722W) also activated MAP kinase kinase in vitro. These findings suggest that one function of c-Raf-1 in mitogenic signaling is to phosphorylate and activate MAP kinase kinase.

An Association between Collateral Blood Flow and Myocardial Viability in Patients with Recent Myocardial Infarction

Abstract: Background. We hypothesized that successful reperfusion of an occluded infarct-related coronary artery even late after acute myocardial infarction would result in improved regional wall motion and that such improvement might be related to the presence of collateral blood flow within the infarct bed. Methods. We assessed regional wall motion by two-dimensional echocardiography at base line and one month after angioplasty was attempted in the occluded infarct-related artery in 43 patients who had had a myocardial infarction two days to five weeks earlier. A wall-motion score was assigned to each patient on a five-point scale (from 1 [normal function] to 5 [dyskinesia]). The percentage of the infarct bed perfused by collateral flow was assessed with myocardial contrast echocardiography. Results. In the 41 patients who had abnormal wall motion at base line, improvement in function was noted in 25 (78 percent) of the 32 in whom angioplasty was successful, as compared with only 1 (11 percent) of the 9 ...

Steiner tree problems

Abstract: We give a survey up to 1989 on the Steiner tree problems which include the four important cases of euclidean, rectilinear, graphic, phylogenetic and some of their generalizations. We also provide a rather comprehensive and up-to-date bibliography which covers more than three hundred items.

Thresholds of quality: implications for the social development of children in center-based child care.

Abstract: We assessed the quality of center child care relationships with adults and peers for 414 children (ages 14 to 54 months). Classrooms were classified by ratio and group size provisions of the Federal Interagency Day Care Requirements (FIDCR) and by the Early Childhood and Infant and Toddler Environmental Rating Scales. Children cared for in classrooms meeting FIDCR ratios were more likely to be in classrooms rated as good or very good in caregiving and activities. Children in classrooms rated as good or very good in caregiving were more likely to be securely attached to teachers. Securely attached children were more competent with peers. Children cared for in classrooms meeting FIDCR group size were more likely to be in classrooms rated higher in activities. Children in classrooms rated high in activities were likely to orient to both adults and peers. Children with social orientations to adults and peers were more competent with peers.

Clinical outcome of radiosurgery for cerebral arteriovenous malformations

Abstract: The clinical outcomes are described for 247 consecutive cases of arteriovenous malformation (AVM) treated with the gamma knife between April, 1970, and December 31, 1983. Headache resolved in 65 (66.3%) of the 98 patients presenting with this symptom and improved in an additional nine (9.2%). Of 59 patients admitted with seizures, 11 (18.6%) became seizure-free without anticonvulsant medication and an additional 30 patients (50.8%) became seizure-free with anticonvulsant medication. Pre-existing neurological deficits improved or totally disappeared following radiosurgery in 56.7% of affected cases. This improvement presumably occurred within the frame of the natural history. The protective effect of the ionizing beams against hemorrhage in incompletely obliterated AVM's is analyzed. To assess the rate of rebleeding, probability estimates were calculated using both the person-year method and the Kaplan-Meier life table. With the person-year method the actual rebleed rate is not too different from the values observed in the natural history of the disease (2% to 3%/yr). Analysis by Kaplan-Meier life-table estimates demonstrated a risk of nearly 3.7%/yr until 60 months after radiosurgery. Five years following treatment, the life table ends in a plateau which could be interpreted as an indication of decrease in the risk of hemorrhage. However, long flat regions at the right end of the life table do not imply that the real risk of rebleeding is negligible unless a large number of patients have been followed well into or beyond the flat region.

Lateral diffusion in the liquid phases of dimyristoylphosphatidylcholine/cholesterol lipid bilayers: a free volume analysis.

Abstract: The technique of fluorescence recovery after photobleaching is used to perform an extensive study of the lateral diffusion of a phospholipid probe in the binary mixture dimyristoylphosphatidylcholine/cholesterol, above the melting temperature of the phospholipid In the regions of the phase diagram where a single liquid phase exists, diffusion can be quantitatively described by free volume theory, using a modified Macedo-Litovitz hybrid equation In the liquid-liquid immiscibility region, the temperature dependence of the diffusion coefficient is in excellent agreement with current theories of generalized diffusivities in composite two-phase media A consistent interpretation of the diffusion data can be provided based essentially on the idea that the primary effect of cholesterol addition to the bilayer is to occupy free volume On this basis, a general interpretation of the phase behavior of this mixture is also proposed

The annexins and exocytosis

Abstract: The annexins are a group of homologous proteins that bind phospholipids in the presence of calcium. They may provide a major pathway for communication between cellular membranes and their cytoplasmic environment. Annexins have a characteristic "bivalent" activity in the sense that they can draw two membranes together when activated by calcium. This has led to the hypothesis that certain members of this protein family may initiate contact and fusion between a secretory vesicle membrane and the plasma membrane during the process of exocytosis.

HLA-A2.1-associated peptides from a mutant cell line: a second pathway of antigen presentation.

Abstract: Peptides extracted from HLA-A2.1 class I major histocompatibility complex (MHC) molecules expressed on the antigen processing mutant CEMx721.174.T2 were characterized by electrospray ionization-tandem mass spectrometry. Only seven dominant peptides were found, in contrast to over 200 associated with HLA-A2.1 on normal cells. These peptides were derived from the signal peptide domains of normal cellular proteins, were usually larger than nine residues, and were also associated with HLA-A2.1 in normal cells. These results suggest that proteolysis of signal peptide domains in the endoplasmic reticulum is a second mechanism for processing and presentation of peptides for association with class I molecules.

Emotional experience and expression in schizophrenia and depression.

Abstract: The emotional responses of schizophrenic, depressed, and normal subjects and whether differences in the emotional responding of these groups depended on how emotional responses were elicited or measured were examined. Twenty-three blunted and 20 nonblunted schizophrenics, 17 unipolar depressed subjects, and 20 normal subjects were exposed to a series of affect-eliciting stimuli. The stimuli varied in valence (positive vs. negative) and in level of cognitive demand. Subjects reported their subjective experiences, and their facial expressions were videotaped. Blunted schizophrenics were the least facially expressive, although their reported subjective experiences did not differ from those of the other groups. The nonblunted schizophrenics were more responsive than the depressed subjects to the positive stimuli, although the two groups did not differ in their clinical ratings of affective flatness.

A Cybernetic Theory of Stress, Coping, and Well-Being in Organizations

Abstract: Many major theories of organizational stress (OS) reflect basic principles of cybernetics, most notably the negative feedback loop. However, these principles are rarely examined in empirical OS research, which focuses predominantly on simple relationships embedded in OS theories. This problem may reflect an implicit rejection of cybernetic principles on conceptual grounds, the absence of specific propositions regarding these principles, methodological difficulties, or some combination of these factors. In any case, the result is a gap between theoretical and empirical OS research, which severely hinders the accumulation of knowledge in this area. This article is intended to narrow this gap by presenting an integrative cybernetic theory of stress, coping, and well-being in organizations, deriving propositions from this theory, and discussing methodological issues in testing this theory.

Teacher-child relationships and the process of adjusting to school

Abstract: Child-teacher relationships show wide-ranging patterns based on affective valence and engagement and are a unique part of school adjustment.

Protective effects of adenosine in myocardial ischemia.

Abstract: Adenosine is released from the myocardium in response to a decrease in the oxygen supply/demand ratio, as is seen in myocardial ischemia; its protective role is manifested by coronary and collateral vessel vasodilation that increase oxygen supply and by multiple effects that act in concert to decrease myocardial oxygen demand (i.e., negative inotropism, chronotropism, and dromotropism). During periods of oxygen deprivation, adenosine enhances energy production via increased glycolytic flux and can act as a substrate for purine salvage to restore cellular energy charge during reperfusion. Adenosine limits the degree of vascular injury during ischemia and reperfusion by inhibition of oxygen radical release from activated neutrophils, thereby preventing endothelial cell damage, and by inhibition of platelet aggregation. These effects help to preserve endothelial cell function and microvascular perfusion. Long-term exposure to adenosine may also induce coronary angiogenesis.

The Evolution of International Society: A Comparative Historical Analysis Reissue with a new introduction by Barry Buzan and Richard Little

Abstract: `This is a real feast of a book. ... a landmark book. It is clear enough to be used as a teaching text, and could make an excellent introduction to the discipline for those courageous enough to revise their courses.' International Affairs `This is a bold, successful and valuable book... It is written with admirable clarity and merciful conciseness.' International Relations `A stunning success. Watson's book is a masterful piece of theoretical and historical analysis.' John A. Vasquez, Rutgers University Adam Watson, who died in 2007, was a former diplomat who in his later academic career became a pioneer of the discipline of international relations. Originally published in 1992, The Evolution of International Society made a major contribution to international theory and to our perception of how relations between states operate, and established Watson’s place within the canon. This acclaimed and uniquely comprehensive work explains how international societies function across time, starting by examining the ancient state systems before turning to look in detail at the current worldwide international society. The book demonstrates that relations between states are not normally anarchic, but are in fact organized and regulated by elaborate rules and practices. In this timely reissue, a new introduction by Barry Buzan and Richard Little assesses Adam Watson's career as a diplomat and examines how his work as a practitioner shaped his subsequent thinking about the nature of international society. It then contextualises Watson's original work, situates it alongside current work in the area and identifies the originality of Watson's key arguments, helping us to understand Watson’s place within the canon.