Showing papers by "Pennsylvania State University published in 1999"

Multiple imputation: a primer:

Abstract: In recent years, multiple imputation has emerged as a convenient and flexible paradigm for analysing data with missing values. Essential features of multiple imputation are reviewed, with answers to frequently asked questions about using the method in practice.

The Human Resource Architecture: Toward a Theory of Human Capital Allocation and Development

Abstract: Recognizing, that not all employees possess knowledge and skills that are of equal strategic importance, we draw on the resource-based view of the firm, human capital theory, and transaction cost economics to develop a human resource architecture of four different employment modes: internal development, acquisition, contracting, and alliance. We use this architecture to derive research questions for studying the relationships among employment modes, employment relationships, human resource configurations, and criteria for competitive advantage.

Prevalence and predictors of risk for type 2 diabetes mellitus and impaired glucose tolerance in polycystic ovary syndrome: A prospective, controlled study in 254 affected women

Abstract: Women with polycystic ovary syndrome (PCOS) are insulin resistant, have insulin secretory defects, and are at high risk for glucose intolerance. We performed this study to determine the prevalence of glucose intolerance and parameters associated with risk for this in PCOS women. Two-hundred and fifty-four PCOS women, aged 14-44 yr, were prospectively evaluated at 2 centers, 1 urban and ethnically diverse (n = 110) and 1 rural and ethnically homogeneous (n = 144). The rural PCOS women were compared to 80 control women of similar weight, ethnicity, and age. A 75-g oral glucose challenge was administered after a 3-day 300-g carbohydrate diet and an overnight fast with 0 and 2 h blood samples for glucose levels. Diabetes was categorized according to WHO criteria. The prevalence of glucose intolerance was 31.1% impaired glucose intolerance (IGT) and 7.5% diabetes. In nonobese PCOS women (body mass index, <27 kg/m2), 10.3% IGT and 1.5% diabetes were found. The prevalence of glucose intolerance was significantly higher in PCOS vs. control women (chi2 = 7.0; P = 0.01; odds ratio = 2.76; 95% confidence interval = 1.23-6.57). Variables most associated with postchallenge glucose levels were fasting glucose levels (P < 0.0001), PCOS status (P = 0.002), waist/hip ratio (P = 0.01), and body mass index (P = 0.021). The American Diabetes Association criteria applied to fasting glucose significantly underdiagnosed diabetes compared to the WHO criteria (3.2% vs. 7.5%; chi2 = 4.7; P = 0.046; odds ratio = 2.48; 95% confidence interval = 1.01-6.69). We conclude that 1) PCOS women are at significantly increased risk for IGT and type 2 diabetes mellitus at all weights and at a young age; 2) these prevalence rates are similar in 2 different populations of PCOS women, suggesting that PCOS may be a more important risk factor than ethnicity or race for glucose intolerance in young women; and 3) the American Diabetes Association diabetes diagnostic criteria failed to detect a significant number of PCOS women with diabetes by postchallenge glucose values.

Development of food preferences

Abstract: Using a developmental systems perspective, this review focuses on how genetic predispositions interact with aspects of the eating environment to produce phenotypic food preferences. Predispositions include the unlearned, reflexive reactions to basic tastes: the preference for sweet and salty tastes, and the rejection of sour and bitter tastes. Other predispositions are ( a) the neophobic reaction to new foods and (b) the ability to learn food preferences based on associations with the contexts and consequences of eating various foods. Whether genetic predispositions are manifested in food preferences that foster healthy diets depends on the eating environment, including food availability and child-feeding practices of the adults. Unfortunately, in the United States today, the ready availability of energy-dense foods, high in sugar, fat, and salt, provides an eating environment that fosters food preferences inconsistent with dietary guidelines, which can promote excess weight gain and obesity.

CO2 Reforming of CH4

Abstract: Although technological practice should minimize environmental impact, this is not always economically feasible. During the past decade, for example, there has been increasing global concern over th...

Subsystems of Second Order Arithmetic

Abstract: List of tables Preface Acknowledgements 1. Introduction Part I. Development of Mathematics within Subsystems of Z2: 2. Recursive comprehension 3. Arithmetical comprehension 4. Weak Konig's lemma 5. Arithmetical transfinite recursion 6. pi11 comprehension Part II. Models of Subsystems of Z2: 7. ss-models 8. omega-models 9. Non-omega-models Part III. Appendix: 10. Additional results Bibliography Index.

Activity Theory as a Framework for Designing Constructivist Learning Environments

Abstract: The epistemic assumptions of constructive learning are different from those of traditional instruction, so classical methods of needs and task analysis are inappropriate for designing constructivist learning environments (CLEs). This paper argues that activity theory provides an appropriate framework for analyzing needs, tasks, and outcomes for designing CLEs. Activity theory is a socio-cultural, socio-historical lens through which designers can analyze human activity systems. It focuses on the interaction of human activity and consciousness within its relevant environmental context. Since conscious learning emerges from activity (performance), not as a precursor to it, CLEs should attempt to replicate the activity structures, tools and sign systems, socio-cultural rules, and community expectations that performers must accommodate while acting on some object of learning. After explicating assumptions of activity theory and briefly describing the components of CLEs, this paper describes a process for using activity theory as a framework for describing the components of an activity system that can be modeled in CLEs.

Infections in patients with diabetes mellitus.

Abstract: Contrary to common belief, the association between diabetes mellitus and increased susceptibility to infection in general is not supported by strong evidence.1,2 However, many specific infections are more common in diabetic patients, and some occur almost exclusively in them. Other infections occur with increased severity and are associated with an increased risk of complications in patients with diabetes. Several aspects of immunity are altered in patients with diabetes. Polymorphonuclear leukocyte function is depressed, particularly when acidosis is also present. Leukocyte adherence, chemotaxis, and phagocytosis may be affected.3–5 Antioxidant systems involved in bactericidal activity may also be impaired.6 The . . .

Risk Perceptions, General Environmental Beliefs, and Willingness to Address Climate Change

Abstract: The research reported here examines the relationship between risk perceptions and willingness to address climate change. The data are a national sample of 1225 mail surveys that include measures of risk perceptions and knowledge tied to climate change, support for voluntary and government actions to address the problem, general environmental beliefs, and demographic variables. Risk perceptions matter in predicting behavioral intentions. Risk perceptions are not a surrogate for general environmental beliefs, but have their own power to account for behavioral intentions. There are four secondary conclusions. First, behavioral intentions regarding climate change are complex and intriguing. People are neither “nonbelievers” who will take no initiatives themselves and oppose all government efforts, nor are they “believers” who promise both to make personal efforts and to vote for every government proposal that promises to address climate change. Second, there are separate demographic sources for voluntary actions compared with voting intentions. Third, recognizing the causes of global warming is a powerful predictor of behavioral intentions independent from believing that climate change will happen and have bad consequences. Finally, the success of the risk perception variables to account for behavioral intentions should encourage greater attention to risk perceptions as independent variables. Risk perceptions and knowledge, however, share the stage with general environmental beliefs and demographic characteristics. Although related, risk perceptions, knowledge, and general environmental beliefs are somewhat independent predictors of behavioral intentions.

Nonstandard optics from quantum space-time

Abstract: We study light propagation in the picture of semiclassical space-time that emerges in canonical quantum gravity in the loop representation. In such a picture, where space-time exhibits a polymerlike structure at microscales, it is natural to expect departures from the perfect nondispersiveness of an ordinary vacuum. We evaluate these departures, computing the modifications to Maxwell's equations due to quantum gravity and showing that under certain circumstances nonvanishing corrections appear that depend on the helicity of propagating waves. These effects could lead to observable cosmological predictions of the discrete nature of quantum space-time. In particular, recent observations of nondispersiveness in the spectra of gamma-ray bursts at various energies could be used to constrain the type of semiclassical state that describes the universe.

Integrated and Decoupled Corporate Social Performance: Management Commitments, External Pressures, and Corporate Ethics Practices

Abstract: Corporations can respond to expectations for socially responsible processes and outcomes in organizationally integrated ways or in easily decoupled fashion. This study focused on a particular type ...

Laccases: A Useful Group of Oxidoreductive Enzymes

Abstract: Using enzymes as decontaminating agents has received great attention. One of the most promising groups of enzymes, laccases, are used to decontaminate phenol-polluted systems and for bio technological applications. Higher plants and fungi, mostly wood-rotting fungi, are the main producers of laccases, but bacterial laccases also have been found. Belonging to the class of phenoloxidases, laccases catalyze the polymerization of several phenolic substances to polymeric products. In addition, they have transformed lignin and lignin-related compounds, showing a very broad substrate specificity. Specific compounds acting as protein-synthesis inducers historically have been used to improve the production of the enzyme. Recent success in fungal molecular and cellular engineering technology has contributed to significantly increase the industrial production of recombinant laccase. Kinetic (Michaelis-Menten parameters, optimum pH, kcat) and stability properties of laccases may vary according to the source of the en...

Positive feedbacks in the fire dynamic of closed canopy tropical forests

Abstract: The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied. Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity. Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest into scrub or savanna.

Were the Good Old Days That Good? Changes in Managerial Stock Ownership Since the Great Depression

Abstract: We document that ownership by officers and directors of publicly traded firms is on average higher today than earlier in the century. Managerial ownership has risen from 13 percent for the universe of exchange-listed corporations in 1935, the earliest year for which such data exist, to 21 percent in 1995. We examine in detail the robustness of the increase and explore hypotheses to explain it. Higher managerial ownership has not substituted for alternative corporate governance mechanisms. Lower volatility and greater hedging opportunities associated with the development of financial markets appear to be important factors explaining the increase in managerial ownership. THE SEPARATION OF OWNERSHIP AND CONTROL of firms has generated an enormous literature since the publication of Berle and Means' The Modern Corporation and Private Property (1932). In both academic and public policy circles, there has been much debate about the consequences of "absentee ownership" (Veblen (1923)) and what policies should be undertaken to remedy the situation. Berle and Means warn that the separation of ownership and control "destroys the very foundation on which the economic order of the past three centuries has rested" and assert that the "[d]ispersion in the ownership of separate enterprises . . . has already proceeded far, it is rapidly increasing, and appears to be an inevitable development" of the modern cor

Full sintering of powdered-metal bodies in a microwave field

Abstract: The use of microwaves to process absorbing materials was studied intensively in the 1970s and 1980s, and has now been applied to a wide variety of materials1,2,3,4. Initially, success in microwave heating and sintering was confined mainly to oxide and some non-oxide ceramics5,6,7,8,9,10,11; but recently the technique has been extended to carbide semimetals12,13,14 used in cutting tools. Here we describe the microwave sintering of powdered metals to full density. We are able to sinter a wide range of standard powdered metals from commercial sources using a 2.45-GHz microwave field, yielding dense products with better mechanical properties than those obtained by conventional heating. These findings are surprising in view of the reflectivity of bulk metals at microwave frequencies. The ability to sinter metals with microwaves should assist in the preparation of high-performance metal parts needed in many industries, for example, in the automotive industry.

New Insights into the Role of Nuclear Factor-κB, a Ubiquitous Transcription Factor in the Initiation of Diseases

Abstract: Nuclear factor-κB (NF-κB) is a ubiquitous transcription factor that governs the expression of genes encoding cytokines, chemokines, growth factors, cell adhesion molecules, and some acute phase proteins in health and in various disease states. NF-κB is activated by several agents, including cytokines, oxidant free radicals, inhaled particles, ultraviolet irradiation, and bacterial or viral products. Inappropriate activation of NF-κB has been linked to inflammatory events associated with autoimmune arthritis, asthma, septic shock, lung fibrosis, glomerulonephritis, atherosclerosis, and AIDS. In contrast, complete and persistent inhibition of NF-κB has been linked directly to apoptosis, inappropriate immune cell development, and delayed cell growth. Therefore, development of modulatory strategies targeting this transcription factor may provide a novel therapeutic tool for the treatment or prevention of various diseases.

Search for Time Variation of the Fine Structure Constant

Abstract: An order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant $\ensuremath{\alpha}$. Applied to a sample of 30 absorption systems, spanning redshifts $0.5lzl1.6$, we derive limits on variations in $\ensuremath{\alpha}$ over a wide range of epochs. For the whole sample, $\ensuremath{\Delta}\ensuremath{\alpha}/\ensuremath{\alpha}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}1.1\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. This deviation is dominated by measurements at $zg1$, where $\ensuremath{\Delta}\ensuremath{\alpha}/\ensuremath{\alpha}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}1.9\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. For $zl1$, $\ensuremath{\Delta}\ensuremath{\alpha}/\ensuremath{\alpha}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}0.2\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. While this is consistent with a time-varying $\ensuremath{\alpha}$, further work is required to explore possible systematic errors in the data, although careful searches have so far revealed none.

Ordered Mesoporous Polymers of Tunable Pore Size from Colloidal Silica Templates

Abstract: Ordered mesoporous polymers have been prepared by replication of colloidal crystals made from silica spheres 35 nanometers in diameter. The pores in the colloidal crystals were filled with divinylbenzene (DVB), ethyleneglycol dimethacrylate (EDMA), or a mixture of the two. Polymerization and subsequent dissolution of the silica template leaves a polycrystalline network of interconnected pores. When mixtures of DVB and EDMA are used, the pore size of the polymer replicas can be varied continuously between 35 and 15 nanometers because the polymer shrinks when the silica template is removed.

Corporate Ethics Programs as Control Systems: Influences of Executive Commitment and Environmental Factors

Abstract: Our study asked why corporations introduce formal programs to manage ethics and why those programs display varying characteristics. We used control theory to delineate an ethics program's scope and...

Using Analysts' Forecasts to Measure Properties of Analysts' Information Environment

Abstract: This paper presents a model that relates properties of the analysts' information environment to the properties of their forecasts. First, we express forecast dispersion and error in the mean forecast in terms of analyst uncertainty and consensus (that is, the degree to which analysts share a common belief). Second, we reverse the relations to show how uncertainty and consensus can be measured by combining forecast dispersion, error in the mean forecast, and the number of forecasts. Third, we show that the quality of common and private information available to analysts can be measured using these same observable variables. The relations we present are intuitive and easily applied in empirical studies.

Screening for dementia with the Memory Impairment Screen

Abstract: Objectives: To validate a sensitive and specific screening test for AD and other dementias, assess its reliability and discriminative validity, and present normative data for its use in various applied settings. Background: To improve discrimination in screening for AD and dementia, we developed the Memory Impairment Screen (MIS), a 4-minute, four-item, delayed free- and cued-recall test of memory impairment. The MIS uses controlled learning to ensure attention, induce specific semantic processing, and optimize encoding specificity to improve detection of dementia. Methods: Equivalent forms of the MIS were given at the beginning and end of the testing session to assess alternate forms reliability. Discriminative validity was assessed in a criterion sample of 483 aged individuals, 50 of whom had dementia according to Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised) criteria. Results: The MIS had good alternate forms reliability, high construct validity for memory impairment, and good discriminative validity in terms of sensitivity, specificity, and positive predictive value. We present normative data for use in settings with different base rates (prevalences) of AD and dementia. Conclusion: The MIS provides efficient, reliable, and valid screening for AD and other dementias.

Complete molecular remissions induced by patient-specific vaccination plus granulocyte-monocyte colony-stimulating factor against lymphoma.

Abstract: Lymphomas express a tumor-specific antigen which can be targeted by cancer vaccination We evaluated the ability of a new idiotype protein vaccine formulation to eradicate residual t(14;18)+ lymphoma cells in 20 patients in a homogeneous, chemotherapy-induced first clinical complete remission All 11 patients with detectable translocations in their primary tumors had cells from the malignant clone detectable in their blood by PCR both at diagnosis and after chemotherapy, despite being in complete remission However, 8 of 11 patients converted to lacking cells in their blood from the malignant clone detectable by PCR after vaccination and sustained their molecular remissions Tumor-specific cytotoxic CD8+ and CD4+ T cells were uniformly found (19 of 20 patients), whereas antibodies were detected, but apparently were not required for molecular remission Vaccination was thus associated with clearance of residual tumor cells from blood and long-term disease-free survival The demonstration of molecular remissions, analysis of cytotoxic T lymphocytes against autologous tumor targets, and addition of granulocyte-monocyte colony-stimulating factor to the vaccine formulation provide principles relevant to the design of future clinical trials of other cancer vaccines administered in a minimal residual disease setting

Understanding Leader Emotional Intelligence and Performance: The Role of Self-Other Agreement on Transformational Leadership Perceptions

Abstract: The purpose of this study was to examine whether self-awareness of managers (defined as agreement between self and other leadership ratings) would moderate relationships between (a) aspects of emot...