Showing papers by "University of Southern California published in 1995"

Psychological empowerment in the workplace: dimensions, measurement, and validation

Abstract: This research begins to develop and validate a multidimensional measure of psychological empowerment in the workplace Second-order confirmatory factor analyses were conducted with two complementary samples to demonstrate the convergent and discriminant validity of four dimensions of empowerment and their contributions to an overall construct of psychological empowerment Structural equations modeling was used to examine a nomological network of psychological empowerment in the workplace Tested hypotheses concerned key antecedents and consequences of the construct Initial support for the construct validity of psychological empowerment was found Directions for future research are discussed

Robust adaptive control

Abstract: 1. Introduction. Control System Design Steps. Adaptive Control. A Brief History. 2. Models for Dynamic Systems. Introduction. State-Space Models. Input/Output Models. Plant Parametric Models. Problems. 3. Stability. Introduction. Preliminaries. Input/Output Stability. Lyapunov Stability. Positive Real Functions and Stability. Stability of LTI Feedback System. Problems. 4. On-Line Parameter Estimation. Introduction. Simple Examples. Adaptive Laws with Normalization. Adaptive Laws with Projection. Bilinear Parametric Model. Hybrid Adaptive Laws. Summary of Adaptive Laws. Parameter Convergence Proofs. Problems. 5. Parameter Identifiers and Adaptive Observers. Introduction. Parameter Identifiers. Adaptive Observers. Adaptive Observer with Auxiliary Input. Adaptive Observers for Nonminimal Plant Models. Parameter Convergence Proofs. Problems. 6. Model Reference Adaptive Control. Introduction. Simple Direct MRAC Schemes. MRC for SISO Plants. Direct MRAC with Unnormalized Adaptive Laws. Direct MRAC with Normalized Adaptive Laws. Indirect MRAC. Relaxation of Assumptions in MRAC. Stability Proofs in MRAC Schemes. Problems. 7. Adaptive Pole Placement Control. Introduction. Simple APPC Schemes. PPC: Known Plant Parameters. Indirect APPC Schemes. Hybrid APPC Schemes. Stabilizability Issues and Modified APPC. Stability Proofs. Problems. 8. Robust Adaptive Laws. Introduction. Plant Uncertainties and Robust Control. Instability Phenomena in Adaptive Systems. Modifications for Robustness: Simple Examples. Robust Adaptive Laws. Summary of Robust Adaptive Laws. Problems. 9. Robust Adaptive Control Schemes. Introduction. Robust Identifiers and Adaptive Observers. Robust MRAC. Performance Improvement of MRAC. Robust APPC Schemes. Adaptive Control of LTV Plants. Adaptive Control for Multivariable Plants. Stability Proofs of Robust MRAC Schemes. Stability Proofs of Robust APPC Schemes. Problems. Appendices. Swapping Lemmas. Optimization Techniques. Bibliography. Index. License Agreement and Limited Warranty.

Narrative configuration in qualitative analysis

Abstract: Narrative inquiry refers to a subset of qualitative research designs in which stories are used to describe human action. The term narrative has been employed by qualitative researchers with a variety of meanings. In the context of narrative inquiry, narrative refers to a discourse form in which events and happenings are configured into a temporal unity by means of a plot. Bruner (1985) designates two types of cognition: paradigmatic, which operates by recognizing elements as members of a category; and narrative, which operates by combining elements into an emplotted story. Narrative inquiries divide into two distinct groups based on Bruner's types of cognition. Paradigmatic‐type narrative inquiry gathers stories for its data and uses paradigmatic analytic procedures to produce taxonomies and categories out of the common elements across the database. Narrative‐type narrative inquiry gathers events and happenings as its data and uses narrative analytic procedures to produce explanatory stories.

Will raising the incomes of all increase the happiness of all

Abstract: Today, as in the past, within a country at a given time those with higher incomes are, on average, happier. However, raising the incomes of all does not increase the happiness of all. This is because the material norms on which judgments of well-being are based increase in the same proportion as the actual income of the society. These conclusions are suggested by data on reported happiness, material norms, and income collected in surveys in a number of countries over the past half century.

Myopic loss aversion and the equity premium puzzle

Abstract: The equity premium puzzle refers to the empirical fact that stocks have outperformed bonds over the last century by a surprisingly large margin. We offer a new explanation based on two behavioral concepts. First, investors are assumed to be "loss averse," meaning that they are distinctly more sensitive to losses than to gains. Second, even long-term investors are assumed to evaluate their portfolios frequently. We dub this combination "myopic loss aversion." Using simulations, we find that the size of the equity premium is consistent with the previously estimated parameters of prospect theory if investors evaluate their portfolios annually. There is an enormous discrepancy between the returns on stocks and fixed income securities. Since 1926 the annual real return on stocks has been about 7 percent, while the real return on treasury bills has been less than 1 percent. As demonstrated by Mehra and Prescott [1985], the combination of a high equity premium, a low risk-free rate, and smooth consumption is difficult to explain with plausible levels of investor risk aversion. Mehra and Prescott estimate that investors would have to have coefficients of relative risk aversion in excess of 30 to explain the historical equity premium, whereas previous estimates and theoretical arguments suggest that the actual figure is close to 1.0. We are left with a pair of questions: why is the equity premium so large, or why is anyone willing to hold bonds? The answer we propose in this paper is based on two concepts from the psychology of decision-making. The first concept is loss aversion. Loss aversion refers to the tendency for individuals to be more sensitive to reductions in their levels of well-being than to increases. The concept plays a central role in Kahneman and Tversky's [1979] descriptive theory of decision-making under

Perspective Making and Perspective Taking in Communities of Knowing

Abstract: Knowledge-intensive firms are composed of multiple communities with specialized expertise, and are often characterized by lateral rather than hierarchical organizational forms. We argue that producing knowledge to create innovative products and processes in such firms requires the ability to make strong perspectives within a community, as well as the ability to take the perspective of another into account. We present models of language, communication and cognition that can assist in the design of electronic communication systems for perspective making and perspective taking. By appreciating how communication is both like a language game played in a local community and also like a transmission of messages through a conduit, and by appreciating how cognition includes a capacity to narrativize our experience as well as a capacity to process information, we identify some guidelines for designing electronic communication systems to support knowledge work. The communication systems we propose emphasize that narratives can help construct strong perspectives within a community of knowing, and that reflecting upon and representing that perspective can create boundary objects which allow for perspective taking between communities. We conclude by describing our vision of an idealized knowledge intensive firm with a strong culture of perspective making and perspective taking, and by identifying some elements of the electronic communication systems we would expect to see in such a firm.

Fuzzy logic systems for engineering: a tutorial

Abstract: A fuzzy logic system (FLS) is unique in that it is able to simultaneously handle numerical data and linguistic knowledge. It is a nonlinear mapping of an input data (feature) vector into a scalar output, i.e., it maps numbers into numbers. Fuzzy set theory and fuzzy logic establish the specifics of the nonlinear mapping. This tutorial paper provides a guided tour through those aspects of fuzzy sets and fuzzy logic that are necessary to synthesize an FLS. It does this by starting with crisp set theory and dual logic and demonstrating how both can be extended to their fuzzy counterparts. Because engineering systems are, for the most part, causal, we impose causality as a constraint on the development of the FLS. After synthesizing a FLS, we demonstrate that it can be expressed mathematically as a linear combination of fuzzy basis functions, and is a nonlinear universal function approximator, a property that it shares with feedforward neural networks. The fuzzy basis function expansion is very powerful because its basis functions can be derived from either numerical data or linguistic knowledge, both of which can be cast into the forms of IF-THEN rules. >

Subpicosecond Measurements of Polar Solvation Dynamics: Coumarin 153 Revisited

Abstract: Time-resolved emission measurements of the solute coumarin 153 (C153) are used to probe the time dependence of solvation in 24 common solvents at room temperature. Significant improvements in experimental time resolution ({approx}100 fs instrument response) as well as corresponding improvements in analysis methods provide confidence that all of the spectral evolution (including both the inertial and the diffusive parts of the response) are observed in these measurements. Extensive data concerning the steady-state solvatochromism of C153, coupled to an examination of the effects of vibrational relaxation, further demonstrate that the spectral dynamics being observed accurately monitor the dynamics of nonspecific solvation. Comparisons to theoretical predictions show that models based on the dielectric response of the pure solvent provide a semiquantitative understanding of the dynamics observed. 156 refs., 26 figs., 5 tabs.

Artificial Intelligence: A Modern Approach

Abstract: Humankind has given itself the scientific name homo sapiens--man the wise--because our mental capacities are so important to our everyday lives and our sense of self. The field of artificial intelligence, or AI, attempts to understand intelligent entities. Thus, one reason to study it is to learn more about ourselves. But unlike philosophy and psychology, which are also concerned with AI strives to build intelligent entities as well as understand them. Another reason to study AI is that these constructed intelligent entities are interesting and useful in their own right. AI has produced many significant and impressive products even at this early stage in its development. Although no one can predict the future in detail, it is clear that computers with human-level intelligence (or better) would have a huge impact on our everyday lives and on the future course of civilization. AI addresses one of the ultimate puzzles. How is it possible for a slow, tiny brain{brain}, whether biological or electronic, to perceive, understand, predict, and manipulate a world far larger and more complicated than itself? How do we go about making something with those properties? These are hard questions, but unlike the search for faster-than-light travel or an antigravity device, the researcher in AI has solid evidence that the quest is possible. All the researcher has to do is look in the mirror to see an example of an intelligent system. AI is one of the newest disciplines. It was formally initiated in 1956, when the name was coined, although at that point work had been under way for about five years. Along with modern genetics, it is regularly cited as the ``field I would most like to be in'' by scientists in other disciplines. A student in physics might reasonably feel that all the good ideas have already been taken by Galileo, Newton, Einstein, and the rest, and that it takes many years of study before one can contribute new ideas. AI, on the other hand, still has openings for a full-time Einstein. The study of intelligence is also one of the oldest disciplines. For over 2000 years, philosophers have tried to understand how seeing, learning, remembering, and reasoning could, or should, be done. The advent of usable computers in the early 1950s turned the learned but armchair speculation concerning these mental faculties into a real experimental and theoretical discipline. Many felt that the new ``Electronic Super-Brains'' had unlimited potential for intelligence. ``Faster Than Einstein'' was a typical headline. But as well as providing a vehicle for creating artificially intelligent entities, the computer provides a tool for testing theories of intelligence, and many theories failed to withstand the test--a case of ``out of the armchair, into the fire.'' AI has turned out to be more difficult than many at first imagined, and modern ideas are much richer, more subtle, and more interesting as a result. AI currently encompasses a huge variety of subfields, from general-purpose areas such as perception and logical reasoning, to specific tasks such as playing chess, proving mathematical theorems, writing poetry{poetry}, and diagnosing diseases. Often, scientists in other fields move gradually into artificial intelligence, where they find the tools and vocabulary to systematize and automate the intellectual tasks on which they have been working all their lives. Similarly, workers in AI can choose to apply their methods to any area of human intellectual endeavor. In this sense, it is truly a universal field.

A Simulation Study of Mediated Effect Measures

Abstract: Analytical solutions for point and variance estimators of the mediated effect, the ratio of the mediated to the direct effect, and the proportion of the total effect that is mediated were studied with statistical simulations. We compared several approximate solutions based on the multivariate delta method and second order Taylor series expansions to the empirical standard deviation of each estimator and theoretical standard error when available. The simulations consisted of 500 replications of three normally distributed variables for eight sample sizes (N = 10, 25, 50, 100, 500, 1000, and 5000) and 64 parameter value combinations. The different solutions for the standard error of the indirect effect were very similar for sample sizes of at least 50, except when the independent variable was dichotomized. A sample size of at least 500 was needed for accurate point and variance estimates of the proportion mediated. The point and variance estimates of the ratio of the mediated to nonmediated effect did not st...

Signal processing with alpha-stable distributions and applications

Abstract: The Stable Distribution Symmetric Stable Random Processes Covariation and Conditional Expectation Parameter Estimates for Symmetric Stable Distributions Estimation of Covariations Parametric Models of Stable Processes Linear Theory of Stable Processes Symmetric Stable Models for Impulsive Noise Signal Detection in Stable Noise Current and Future Trends in Signal Processing with Alpha-Stable Distributions.

Normative Influences on Impulsive Buying Behavior

Abstract: Although consumer researchers have investigated impulse buying for nearly 50 years, almost no research has empirically examined its normative aspects. This article presents conceptual and empirical evidence that consumers' normative evaluations (i.e., judgments about the appropriateness of engaging in impulse buying behavior) moderate the relationship between the impulse buying trait and consumers' buying behaviors. Specifically, the relationship between the buying impulsiveness trait and related buying behaviors is significant only when consumers believe that acting on impulse is appropriate. The findings from two studies across student and retail customer samples converge and support the hypothesized moderating role of consumers' normative evaluations.

Vertically Self-Organized InAs Quantum Box Islands on GaAs(100)

Abstract: Coherent InAs islands separated by GaAs spacer layers are shown to exhibit self-organized growth along the vertical (i.e., growth) direction. The driving force for such vertically self-organized growth is shown to be the interacting strain fields induced by the islands which give rise to a preferred direction for In migration. A model analysis accounting for the mechanochemical surface diffusion gives an island average size and average separation dependent characteristic spacer layer thickness ${z}_{0}$ below which a vertically self-organized growth occurs.

Aggressive Behavior and Altered Amounts of Brain Serotonin and Norepinephrine in Mice Lacking MAOA

Abstract: Deficiency in monoamine oxidase A (MAOA), an enzyme that degrades serotonin and norepinephrine, has recently been shown to be associated with aggressive behavior in men of a Dutch family. A line of transgenic mice was isolated in which transgene integration caused a deletion in the gene encoding MAOA, providing an animal model of MAOA deficiency. In pup brains, serotonin concentrations were increased up to ninefold, and serotonin-like immunoreactivity was present in catecholaminergic neurons. In pup and adult brains, norepinephrine concentrations were increased up to twofold, and cytoarchitectural changes were observed in the somatosensory cortex. Pup behavioral alterations, including trembling, difficulty in righting, and fearfulness were reversed by the serotonin synthesis inhibitor parachlorophenylalanine. Adults manifested a distinct behavioral syndrome, including enhanced aggression in males.

Abnormal lung development and cleft palate in mice lacking TGF-beta 3 indicates defects of epithelial-mesenchymal interaction.

Abstract: A broad spectrum of biological activities has been proposed for transforming growth factor-beta 3 (TGF-beta 3). To study TGF-beta 3 function in development, TGF-beta 3 null mutant mice were generated by gene-targeting. Within 20 hours of birth, homozygous TGF-beta 3-/- mice die with unique and consistent phenotypic features including delayed pulmonary development and defective palatogenesis. Unlike other null mutants with cleft palate, TGF-beta 3-/- mice lack other concomitant craniofacial abnormalities. This study demonstrates an essential function for TGF-beta 3 in the normal morphogenesis of palate and lung, and directly implicates this cytokine in mechanisms of epithelial-mesenchymal interaction.

The Effects of Temperature and ƒ O 2 on the Al-in-Hornblende Barometer

Abstract: The AI-in-hornblende barometer potentially offers a basis for estimating crystallization pressure for granitic batholiths. However, owing to the simplicity of its formulation, misuse of the barometer can occur. Many granitic intrusions are emplaced at conditions inconsistent with those of the existing experimental calibrations, including f02 2 kbar at typical crustal pressures. For the Mount Stuart batholith, consideration of temperature yields revised pressures that are in agreement with pressures obtained from wall rocks and eliminates much of the apparent domal structure. Low-f02 granites have amphibole Fe/(Fe + Mg) ratios that exceed the typical 0.40-0.65 range used in most experimental and empirical calibrations. Examples from anorogenic granitic batholiths of mid-Proterozoic age yield pressures that are too high by a factor of two to three in comparison with pressures obtained from adjacent metamorphic assemblages. Hornblende in these granites not only has high Fe/(Fe + Mg) but also low ratios of FeH to Fe2+. The anomalously high Al in Fe-rich, FeH -poor hornblende is inferred to be the result of increased [6JAIoccupancy of the M2 site not buffered by the Mg and FeH abundances typical of amphiboles in calc-alkaline and other high- f02 plutonic rocks.

Ethnicity and Attitudes Toward Patient Autonomy

Abstract: Objective. —To study differences in the attitudes of elderly subjects from different ethnic groups toward disclosure of the diagnosis and prognosis of a terminal illness and toward end-of-life decision making. Design. —Survey. Setting. —Thirty-one senior citizen centers within Los Angeles County, California. Respondents. —A stratified quota sample of 200 subjects aged 65 years and older self-identified as being from each of four ethnic groups: European American, African American, Korean American, or Mexican American (N=800). Main Outcome Measures and Results. —Korean Americans (47%) and Mexican Americans (65%) were significantly less likely than European Americans (87%) and African Americans (88%) to believe that a patient should be told the diagnosis of metastatic cancer. Korean Americans (35%) and Mexican Americans (48%) were less likely than African Americans (63%) and European Americans (69%) to believe that a patient should be told of a terminal prognosis and less likely to believe that the patient should make decisions about the use of life-supporting technology (28% and 41% vs 60% and 65%). Instead, Korean Americans and Mexican Americans tended to believe that the family should make decisions about the use of life support. On stepwise multiple logistic regression, ethnicity was the primary factor related to attitudes toward truth telling and patient decision making. Conclusions. —Korean-American and Mexican-American subjects were more likely to hold a family-centered model of medical decision making rather than the patient autonomy model favored by most of the African-American and European-American subjects. This finding suggests that physicians should ask their patients if they wish to receive information and make decisions or if they prefer that their families handle such matters. (JAMA. 1995;274:820-825)

Molecular alterations of the AKT2 oncogene in ovarian and breast carcinomas.

Abstract: The AKT2 gene is one of the human homologues of v-akt, the transduced oncogene of the AKT8 virus, which induces lymphomas in mice. In previous studies, AKT2, which codes for a serine-threonine protein kinase, was shown to be amplified and overexpressed in some human ovarian carcinoma cell lines and amplified in primary tumors of the ovary. To confirm and extend these findings, we conducted a large-scale, multicenter study of AKT2 alterations in ovarian and breast cancer. Southern-blot analysis demonstrated AKT2 amplification in 16 of 132 (12.1%) ovarian carcinomas and in 3 of 106 (2.8%) breast carcinomas. No AKT2 alteration was detected in 24 benign or borderline tumors. Northern-blot analysis revealed overexpression of AKT2 in 3 of 25 fresh ovarian carcinomas which were negative for AKT2 amplification. The difference in the incidence of AKT2 alterations in ovarian and breast cancer suggests a specific role for this gene in ovarian oncogenesis. No significant association was found between AKT2 amplification and amplification of the proto-oncogenes MYC and ERBB2, suggesting that amplification of AKT2 defines an independent subset of breast and ovarian cancers. Ovarian cancer patients with AKT2 alterations appear to have a poor prognosis. Amplification of AKT2 was especially frequent in undifferentiated tumors (4 of 8, p = 0.019), suggesting that AKT2 alterations may be associated with tumor aggressiveness.

High-order neural network structures for identification of dynamical systems

Abstract: Several continuous-time and discrete-time recurrent neural network models have been developed and applied to various engineering problems. One of the difficulties encountered in the application of recurrent networks is the derivation of efficient learning algorithms that also guarantee the stability of the overall system. This paper studies the approximation and learning properties of one class of recurrent networks, known as high-order neural networks; and applies these architectures to the identification of dynamical systems. In recurrent high-order neural networks, the dynamic components are distributed throughout the network in the form of dynamic neurons. It is shown that if enough high-order connections are allowed then this network is capable of approximating arbitrary dynamical systems. Identification schemes based on high-order network architectures are designed and analyzed. >

A reliable multicast framework for light-weight sessions and application level framing

Abstract: This paper describes SRM (Scalable Reliable Multicast), a reliable multicast framework for application level framing and light-weight sessions. The algorithms of this framework are efficient, robust, and scale well to both very large networks and very large sessions. The framework has been prototyped in wb, a distributed whiteboard application, and has been extensively tested on a global scale with sessions ranging from a few to more than 1000 participants. The paper describes the principles that have guided our design, including the IP multicast group delivery model, an end-to-end, receiver-based model of reliability, and the application level framing protocol model. As with unicast communications, the performance of a reliable multicast delivery algorithm depends on the underlying topology and operational environment. We investigate that dependence via analysis and simulation, and demonstrate an adaptive algorithm that uses the results of previous loss recovery events to adapt the control parameters used for future loss recovery. With the adaptive algorithm, our reliable multicast delivery algorithm provides good performance over a wide range of underlying topologies.

Inclusion body myositis and myopathies.

Abstract: Preface Part I. Overview of Pathologic and Pathogenic Comparison Between Sporadic Inclusion-Body Myositis and Hereditary Inclusion-Body Myopathies: 1. Newest approaches to diagnosis and pathogenesis of sporadic inclusion-body myositis and hereditary inclusion-body myopathies, including molecular-pathologic similarities to Alzheimer disease Part II. Historical Perspective: 2: Evolving concepts of inclusion-body myositis Part III. Sporadic Inclusion-Body Myositis - Clinical and Diagnostic Considerations: 3: Sporadic inclusion-body myositis: Clinical and laboratory features and diagnostic criteria 4: Inclusion-body myositis: natural history 5: Uncommon clinico-pathological forms of sporadic inclusion-body myositis: Report of four cases 6: Inclusion-body myositis: pathological changes 7: Unusual pathological forms of inclusion-body myositis, and neuromuscular disorders with IBM-like changes 8: Electrophysiological findings in inclusion-body myositis 9: Genetic factors in sporadic inclusion-body myositis Part IV. Hereditary Inclusion-Body Myopathies - Clinical and Diagnostic Considerations: 10: Hereditary inclusion-body myopathy in Jews of Persian origin: Clinical and laboratory data 11. Hereditary inclusion-body myopathy (h-IBM) with quadriceps sparing: epidemiology and genetics 12: Familial autosomal-recessive inclusion-body myositis with asymptomatic leukoencephalopathy 13: Welander distal myopathy - clinical, pathophysiological, and molecular aspects 14. Tibial muscular dystrophy - clinical, genetic, and morphological characteristics 15. Distal myopathy with rimmed vacuoles, inclusion-body myositis and related disorders in Japan 16. Inclusion-body myopathies 17. Is the muscle fiber in inclusion body-myositis an antigen-presenting cell of an innocent bystander? 18. Viruses, immunodeficiency and inclusion-body myositis 19. Myonuclear abnormalities may play a central role in the pathogenesis of muscle fiber damage in inclusion-body myositis 20. Nuclear degeneration and rimmed vacuole formation in neuromuscular disorders 21. Mitochondrial alterations in sporadic inclusion-body myositis 22. mtDNA analysis in muscle of patients with sporadic inclusion-body myopathy Part V. Treatment: 23. Evaluation of treatment for sporadic inclusion-body myositis 24. Personal experience in treating sporadic inclusion-body myositis Subject index.

Functional mapping of sequence learning in normal humans

Abstract: The brain localization of motor sequence learning was studied in normal subjects with positron emission tomography. Subjects performed a serial reaction time (SRT) task by responding to a series of stimuli that occurred at four different spatial positions. The stimulus locations were either determined randomly or according to a 6-element sequence that cycled continuously. The SRT task was performed under two conditions. With attentional interference from a secondary counting task there was no development of awareness of the sequence. Learning-related increases of cerebral blood flow were located in contralateral motor effector areas including motor cortex, supplementary motor area, and putamen, consistent with the hypothesis that nondeclarative motor learning occurs in cerebral areas that control limb movements. Additional cortical sites included the rostral prefrontal cortex and parietal cortex. The SRT learning task was then repeated with a new sequence and no attentional interference. In this condition, 7 of 12 subjects developed awareness of the sequence. Learning-related blood flow increases were present in right dorsolateral prefrontal cortex, right premotor cortex, right ventral putamen, and biparieto-occipital cortex. The right dorsolateral prefrontal and parietal areas have been previously implicated in spatial working memory and right prefrontal cortex is also implicated in retrieval tasks of verbal episodic memory. Awareness of the sequence at the end of learning was associated with greater activity in bilateral parietal, superior temporal, and right premotor cortex. Motor learning can take place in different cerebral areas, contingent on the attentional demands of the task.

Vendor Consideration and Switching Behavior for Buyers in High-Technology Markets:

Abstract: High-technology markets represent unique problems for organizational buyers and, in turn, for their existing and potential vendors. These problems are due to high levels of uncertainty and the pres...

Use of electrochemical impedance spectroscopy for the study of corrosion protection by polymer coatings

Abstract: A discussion of the requirements for hardware and software necessary for collection and analysis of electrochemical impedance spectroscopy data for polymer coated metals is presented. Most authors agree that a simple model can describe the frequency dependence of impedance spectra for polymer coated metals exposed to corrosive environments. The water uptake of the coating can be estimated from the time dependence of the coating capacitance C c, The pore resistance R po depends both on the resistivity ρ of the coating and the disbonded area A d. The polarization resistance R P of the corroding area under the coating and the corresponding capacitance C dl both depend on A d. The breakpoint frequency method is discussed in detail and the dependence of the breakpoint frequency f b on ρ and A d is derived. In addition to f b other parameters can be obtained which depend on the ratio A d/ρ or only on A d or ρ. Since these parameters can be obtained at frequencies exceeding 1 Hz without the need for an analysis of the impedance spectra in the entire frequency region, this approach is considered especially useful for corrosion monitoring. The concepts proposed for the analysis and interpretation of EIS data for polymer coated metals are illustrated using data for Al alloys, Mg and steel exposed to NaCl. For an alkyd coating on cold rolled steel the time dependence of A d and ρ during exposure to 0.5 m NaCl has been determined qualitatively using the modified breakpoint frequency method.

Engraftment of gene-modified umbilical cord blood cells in neonates with adenosine deaminase deficiency.

Abstract: Haematopoietic stem cells in umbilical cord blood are an attractive target for gene therapy of inborn errors of metabolism. Three neonates with severe combined immunodeficiency were treated by retroviral-mediated transduction of the CD34+ cells from their umbilical cord blood with a normal human adenosine deaminase complementary DNA followed by autologous transplantation. The continued presence and expression of the introduced gene in leukocytes from bone marrow and peripheral blood for 18 months demonstrates that umbilical cord blood cells may be genetically modified with retroviral vectors and engrafted in neonates for gene therapy.

Endoscopic Ligation Compared with Sclerotherapy for Treatment of Esophageal Variceal Bleeding: A Meta-Analysis

Abstract: Purpose To compare the effect of endoscopic ligation with that of sclerotherapy in the treatment of patients with bleeding esophageal varices. Data sources Strategies to identify published and unpublished research included searches of computerized bibliographic and scientific citations, review of citations in relevant primary articles, searches of services providing information on unpublished studies, contact with primary investigators and the ligation equipment manufacturer, and review of proceedings from pertinent scientific meetings. Study selection From 158 potentially relevant articles, duplicate independent review identified 7 relevant randomized trials that compared endoscopic ligation with sclerotherapy for the treatment of patients with bleeding esophageal varices. Data abstraction Independent, duplicate data abstraction of the population, intervention, outcome, and methodologic quality of the trials was done. Data synthesis Ligation therapy compared with sclerotherapy reduced the rebleeding rate (odds ratio, 0.52 [95% CI, 0.37 to 0.74]), the mortality rate (odds ratio, 0.67 [CI, 0.46 to 0.98]), and the rate of death due to bleeding (odds ratio, 0.49 [CI, 0.24 to 0.996]). Four patients would need to be treated with ligation instead of sclerotherapy to avert one rebleeding episode, and 10 would need to be treated with ligation instead of sclerotherapy to prevent one death. Esophageal strictures occurred less frequently with ligation (odds ratio, 0.10 [CI, 0.03 to 0.29]), but no significant differences were seen between treatments for pulmonary infections or bacterial peritonitis. Additionally, the number of endoscopic treatment sessions required to achieve variceal obliteration was lower with ligation than with sclerotherapy. Conclusions On the basis of lower rates of rebleeding, mortality, and complications and the need for fewer endoscopic treatments, ligation should be considered the endoscopic treatment of choice for patients with esophageal variceal bleeding.

Cost models for future software life cycle processes: COCOMO 2.0

Abstract: Current software cost estimation models, such as the 1981 Constructive Cost Model (COCOMO) for software cost estimation and its 1987 Ada COCOMO update, have been experiencing increasing difficulties in estimating the costs of software developed to new life cycle processes and capabilities. These include non-sequential and rapid-development process models; reuse-driven approaches involving commercial off-the-shelf (COTS) packages, re-engineering, applications composition, and applications generation capabilities; object-oriented approaches supported by distributed middleware; and software process maturity initiatives. This paper summarizes research in deriving a baseline COCOMO 2.0 model tailored to these new forms of software development, including rationale for the model decisions. The major new modeling capabilities of COCOMO 2.0 are a tailorable family of software sizing models, involving Object Points, Function Points, and Source Lines of Code; nonlinear models for software reuse and re-engineering; an exponentdriver approach for modeling relative software diseconomies of scale; and several additions, deletions and updates to previous COCOMO effort-multiplier cost drivers. This model is serving as a framework for an extensive current data collection and analysis effort to further refine and calibrate the model's estimation capabilities.