Showing papers by "University of Maryland, College Park published in 1997"

The value of the world's ecosystem services and natural capital

Abstract: The services of ecological systems and the natural capital stocks that produce them are critical to the functioning of the Earth's life-support system. They contribute to human welfare, both directly and indirectly, and therefore represent part of the total economic value of the planet. We have estimated the current economic value of 17 ecosystem services for 16 biomes, based on published studies and a few original calculations. For the entire biosphere, the value (most of which is outside the market) is estimated to be in the range of US$16-54 trillion (10^(12)) per year, with an average of US$33 trillion per year. Because of the nature of the uncertainties, this must be considered a minimum estimate. Global gross national product total is around US$18 trillion per year.

Does Social Capital Have an Economic Payoff? A Cross-Country Investigation

Abstract: This paper presents evidence that "social capital" matters for measurable economic performance, using indicators of trust and civic norms from the World Values Surveys for a sample of 29 market economies. Memberships in formal groups—Putnam's measure of social capital—is not associated with trust or with improved economic performance. We find trust and civic norms are stronger in nations with higher and more equal incomes, with institutions that restrain predatory actions of chief executives, and with better-educated and ethnically homogeneous populations.

The Natural Flow Regime

Abstract: H umans have long been fascinated by the dynamism of free-flowing waters. Yet we have expended great effort to tame rivers for transportation, water supply, flood control, agriculture, and power generation. It is now recognized that harnessing of streams and rivers comes at great cost: Many rivers no longer support socially valued native species or sustain healthy ecosystems that provide important goods and services (Naiman et al. 1995, NRC 1992).

Heart rate variability: Origins, methods, and interpretive caveats

Abstract: Components of heart rate variability have attracted considerable attention in psychology and medicine and have become important dependent measures in psychophysiology and behavioral medicine. Quantification and interpretation of heart rate variability, however, remain complex issues and are fraught with pitfalls. The present report (a) examines the physiological origins and mechanisms of heart rate variability, (b) considers quantitative approaches to measurement, and (c) highlights important caveats in the interpretation of heart rate variability. Summary guidelines for research in this area are outlined, and suggestions and prospects for future developments are considered.

Empirical Performance of Alternative Option Pricing Models

Abstract: Substantial progress has been made in developing more realistic option pricing models. Empirically, however, it is not known whether and by how much each generalization improves option pricing and hedging. We fill this gap by first deriving an option model that allows volatility, interest rates and jumps to be stochastic. Using S&P 500 options, we examine several alternative models from three perspectives: (1) internal consistency of implied parameters/volatility with relevant timeseries data, (2) out-of-sample pricing, and (3) hedging. Overall, incorporating stochastic volatility and jumps is important for pricing and internal consistency. But for hedging, modeling stochastic volatility alone yields the best performance. IN THE LAST TWO DECADES, option pricing has witnessed an explosion of new

A Guide to Conducting Consensual Qualitative Research

Abstract: The authors discuss the components of consensual qualitative research (CQR) using open-ended questions to gather data, using words to describe phenomena, studying a few cases intensively, recognizing the importance of context, using an inductive analytic process, using a team and making decisions by consensus, using auditors, and verifying results by systematically checking against the raw data. The three steps for conducting CQR are developing and coding domains, constructing core ideas, and developing categories to describe consistencies across cases (cross analysis). Criteria for evaluating CQR are trustworthiness of the method, coherence of the results, representativeness of the results to the sample, testimonial validity, applicability of the results, and replicability across samples. Finally, the authors discuss implications for research, practice, and training.

A highly adaptive distributed routing algorithm for mobile wireless networks

Abstract: We present a new distributed routing protocol for mobile, multihop, wireless networks. The protocol is one of a family of protocols which we term "link reversal" algorithms. The protocol's reaction is structured as a temporally-ordered sequence of diffusing computations; each computation consisting of a sequence of directed link reversals. The protocol is highly adaptive, efficient and scalable; being best-suited for use in large, dense, mobile networks. In these networks, the protocol's reaction to link failures typically involves only a localized "single pass" of the distributed algorithm. This capability is unique among protocols which are stable in the face of network partitions, and results in the protocol's high degree of adaptivity. This desirable behavior is achieved through the novel use of a "physical or logical clock" to establish the "temporal order" of topological change events which is used to structure (or order) the algorithm's reaction to topological changes. We refer to the protocol as the temporally-ordered routing algorithm (TORA).

A stitch in time: Self-regulation and proactive coping.

Abstract: In a conceptual and temporal framework, derived from research on social cognition, social interaction, and stress and coping, the authors analyze the processes through which people anticipate or detect potential stressors and act in advance to prevent them or to mute their impact (proactive coping). The framework specifies five stages in proactive coping: (1) resource accumulation, (2) recognition of potential stressors, (3) initial appraisal, (4) preliminary coping efforts, and (5) elicitation and use of feedback concerning initial efforts. The authors detail the role of individual differences skills, and resources at each stage. They highlight the unique predictions afforded by a focus on proactive coping and the importance of understanding how people avoid and offset potential stressors.

The Corporate Social-Financial Performance Relationship: A Typology and Analysis

Abstract: This research note analyzes the relationship between indicators of corporate social and financial performance within a comprehensive theoretical framework. The results, based on data for 67 large U.S. corporations for 1982-1992, reveal no significant negative social-financial performance relationships and strong positive correlations in both contemporaneous and lead-lag formulations.

Relations of Children's Motivation for Reading to the Amount and Breadth of Their Reading.

Abstract: The authors explored different aspects of children's reading motivation and how children's motivation related to the amount and breadth of their reading. The reading motives assessed included self-efficacy, intrinsic-extrinsic motivation and goals, and social aspects. Fourth- and 5th-grade children (N = 105) completed a new reading motivation questionnaire twice during a school year. Children's reading amount and breadth were measured using diaries and questionnaires. Children's reading motivation was found to be multidimensional. Their motivation predicted children's reading amount and breadth even when previous amount and breadth were controlled. An intrinsic motivation composite predicted amount and breadth of reading more strongly than did an extrinsic motivation composite. Some aspects of girls' reading motivation were more positive than boys'. Students' reading amount and breadth contribute substantially to several valued aspects of their achievement and performance, such as reading achievement, world knowledge, and participation in society. Anderson, Wilson, and Fielding (1988) found that the amount of independent out-of-school reading accounted for 16% of the variance in the reading comprehension of fifth graders, after general activity levels were controlled. Similarly, Stanovich and Cunningham (1992) found that amount and breadth of reading predicted reading achievement, as indicated by standardized vocabulary tests, even after previous general intelligence was controlled. Both Anderson et al. and Cipielewski and Stanovich (1992) found that the amount of reading predicted growth of reading achievement during elementary school on different measures of reading comprehension (Cipielewski & Stanovich, 1992). Children's reading amount and breadth contribute to their knowledge of the world, including knowledge of information such as the size of the National Aeronautics and Space Administration budget, who were allies in World War II, and the distinctions among various religious beliefs (Stanovich & Cunningham, 1993). Individuals who read frequently also

Student motivation in middle school: The role of perceived pedagogical caring.

Abstract: This study examined adolescents' perceptions of pedagogical caring in relation to their motivation to achieve positive social and academic outcomes in middle school. A longitudinal sample of 248 students was followed from 6th to 8th grade. Perceived caring from teachers predicted motivational outcom

Principles of Plasma Spectroscopy

Abstract: The diagnosis of plasmas using spectroscopic observations has its origins in various older disciplines, including astronomy and discharge physics. As laboratory plasma physics evolved from low-density, low-temperature discharges to higher energy density plasmas, the need for non-interfering diagnostics arose and spectroscopy was applied to determine the physical state and chemical abundance of the plasmas studied.

Signal stability-based adaptive routing (SSA) for ad hoc mobile networks

Abstract: Ad hoc networks have no spatial hierarchy and suffer from frequent link failures which prevent mobile hosts from using traditional routing schemes. Under these conditions, mobile hosts must find routes to destinations without the use of designated routers and also must dynamically adapt the routes to the current link conditions. This article proposes a distributed adaptive routing protocol for finding and maintaining stable routes based on signal strength and location stability in an ad hoc network and presents an architecture for its implementation. Interoperability with mobile IP (Internet protocol) is discussed.

Ecological Theory and Community Restoration Ecology

Abstract: Community ecological theory may play an important role in the development of a science of restoration ecology. Not only will the practice of restoration benefit from an increased focus on theory, but basic research in community ecology will also benefit. We pose several major thematic questions that are relevant to restoration from the perspective of community ecological theory and, for each, identify specific areas that are in critical need of further research to advance the science of restoration ecology. We ask, what are appropriate restoration endpoints from a community ecology perspective? The problem of measuring restoration at the community level, particularly given the high amount of variability inherent in most natural communities, is not easy, and may require a focus on restoration of community function (e.g., trophic structure) rather than a focus on the restoration of particular species. We ask, what are the benefits and limitations of using species composition or biodiversity measures as endpoints in restoration ecology? Since reestablishing all native species may rarely be possible, research is needed on the relationship between species richness and community stability of restored sites and on functional redundancy among species in regional colonist “pools.” Efforts targeted at restoring system function must take into account the role of individual species, particularly if some species play a disproportionate role in processing material or are strong interactors. We ask, is restoration of habitat a sufficient approach to reestablish species and function? Many untested assumptions concerning the relationship between physical habitat structure and restoration ecology are being made in practical restoration efforts. We need rigorous testing of these assumptions, particularly to determine how generally they apply to different taxa and habitats. We ask, to what extent can empirical and theoretical work on community succession and dispersal contribute to restoration ecology? We distinguish systems in which succession theory may be broadly applicable from those in which it is probably not. If community development is highly predictable, it may be feasible to manipulate natural succession processes to accelerate restoration. We close by stressing that the science of restoration ecology is so intertwined with basic ecological theory that practical restoration efforts should rely heavily on what is known from theoretical and empirical research on how communities develop and are structured over time.

Change in Children's Competence Beliefs and Subjective Task Values across the Elementary School Years: A 3-Year Study.

Abstract: The authors assessed change over 3 years in elementary school children's competence beliefs and subjective task value in the domains of math, reading, instrumental music, and sports. The longitudinal sample consisted of approximately 615 mostly White, lower middle to middle-class children. Stability correlations indicated moderate to strong stability in children's beliefs, especially older children's competence beliefs. The relation of children's ratings of their competence in each domain to estimates of their competence in those domains provided by both parents and teachers increased over the early elementary grades. Children's competence beliefs and ratings of the usefulness and importance of each activity decreased over time. Children's interest in reading and instrumental music decreased, but their interest in sports and math did not. Gender differences in children's competence beliefs and subjective task values did not change over time.

Age and gender comparisons of muscle strength in 654 women and men aged 20-93 yr.

Abstract: Lindle, R. S., E. J. Metter, N. A. Lynch, J. L. Fleg, J. L. Fozard, J. Tobin, T. A. Roy, and B. F. Hurley. Age and gender comparisons of muscle strength in 654 women and men aged 20–93 yr.J. Appl. ...

Deeply Virtual Compton Scattering

Abstract: We study in QCD the physics of deeply virtual Compton scattering (DVCS){emdash}the virtual Compton process in the large s and small t kinematic region. We show that DVCS can probe a new type of {ital off-forward} parton distributions. We derive an Altarelli-Parisi-type of evolution equations for these distributions. We also derive their sum rules in terms of nucleon form factors of the twist-two quark and gluon operators. In particular, we find that the second sum rule is related to fractions of the nucleon spin carried separately by quarks and gluons. We estimate the cross section for DVCS and compare it with the accompanying Bethe-Heitler process at CEBAF and HERMES kinematics. {copyright} {ital 1997} {ital The American Physical Society}

Why don't poor countries catch up? a cross-national test of an institutional explanation

Abstract: Early neoclassical analyses predicted that poor countries would grow faster than wealthy countries, because of technological advances and diminishing returns to capital in the latter. The reverse has occurred: poor countries are falling back rather than catching up. We suggest here that deficient institutions underlie this divergence. Employing various indicators of institutional quality, including the rule of law, the pervasiveness of corruption, and the risk of expropriation and contract repudiation, we show that the ability of poor countries to catch up is determined in large part by the institutional environment in which economic activity in these countries takes place. (JEL O00, O10)

Antecedents and consequences of sexual harassment in organizations: A test of an integrated model.

Abstract: Sexual harassment of women in organizational settings has recently become a topic of interest to researchers and the general public alike. Although numerous studies document its frequency, the development of conceptual models identifying antecedents and consequences of harassment has proceeded at a slower pace. In this article, an empirical test of a recently proposed conceptual model is described. According to the model, organizational climate for sexual harassment and job gender context are critical antecedents of sexual harassment; harassment, in turn, influences work-related variables (e.g., job satisfaction); psychological states (e.g., anxiety and depression); and physical health. On the basis of a sample of women employed at a large, regulated utility company, the model's predictions were generally supported.

Instrument Relevance in Multivariate Linear Models: A Simple Measure

Abstract: The correlation between instruments and explanatory variables is a key determinant of the performance of the instrumental variables estimator. The R2 from regressing the explanatory variable on the instrument vector is a useful measure of relevance in univariate models, but can be misleading when there are multiple endogenous variables. This note proposes a computationally simple partial R2 measure of instrument relevance for multivariate models.

Friendships, Peer Acceptance, and Group Membership: Relations to Academic Achievement in Middle School

Abstract: Two samples of sixth-grade students were followed over time to examine relations of number of reciprocated friendships, peer acceptance, and group membership to academic achievement. In both samples, group membership was the most consistent predictor of grades over time. In Study 2, prosocial behavior, antisocial behavior, and emotional distress were examined as processes that might explain these significant links between peer relationships and academic achievement. Results of longitudinal analyses support a conclusion that aspects of peer relationships are related to classroom achievement indirectly, by way of significant relations with prosocial behavior. Future research might benefit from more in-depth analyses of the functions of adolescent peer relationships and the processes by which they influence orientations toward social and academic competence at school.

EGRET Observations of the Diffuse Gamma-Ray Emission from the Galactic Plane

Abstract: The high-energy diffuse gamma-ray emission from the Galactic plane, |b| ≤ 10°, is studied using observations from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory. The spatial distribution of the diffuse emission has been determined for four broad energy ranges after removing the contribution from point sources detected with greater than 5 σ significance. The longitude and latitude distributions of the intensity, averaged over 4° latitude ranges and 10° longitude ranges, respectively, are shown for the four energy ranges. Spectra of the diffuse emission in 11 energy bands, covering the energy range 30 MeV to 30 GeV, were determined for 10° × 4° (l × b) bins after correcting for the finite EGRET angular resolution. The average spectrum from the direction of the inner Galaxy is shown for 29 energy bands, covering the energy range 30 MeV to 50 GeV. At latitudes |b| > 2°, corresponding to gamma rays emitted within about 3 kpc of the Sun, there is no significant variation in the spectra with Galactic longitude. Comparison of the spectra from the Galactic plane (|b| < 2°) reveals no significant variation with Galactic longitude below about 4 GeV, which suggests that the cosmic-ray electron to proton ratio does not vary significantly throughout the Galaxy. Above 4 GeV, however, there is weak (about 3 σ) evidence for variation of the Galactic plane (|b| < 2°) spectrum with longitude. The spectrum is softer in the direction of the outer Galaxy by about E compared to the spectrum from the inner Galaxy. This variation of the diffuse gamma-ray emission hints at a variation of the cosmic-ray proton spectrum with Galactic radius, which might be expected if cosmic rays are accelerated primarily in the inner Galaxy and then propagate to the outer Galaxy or if the high-energy cosmic rays are confined less well in the outer Galaxy. The spatial and spectral distributions of the diffuse emission are compared with a model calculation of this emission based on dynamic balance and realistic interstellar matter and photon distributions. The spatial comparison is used to establish the value of the molecular mass calibrating ratio N(H2)/WCO and the cosmic-ray/matter coupling scale r0, which are the only adjustable parameters of the model. Comparisons with the observations indicates N(H2)/WCO = (1.56 ± 0.05) × 1020 mol cm-2 (K km s-1)-1 and r0 = (1.76 ± 0.2) kpc. The spatial agreement between this model and the observation is very good. However, above about 1 GeV the integral intensity predicted by the model is about 60% less than the observed intensity. Although the explanation of this excess is unclear, uncertainties in the neutral pion production function or variations in the cosmic-ray spectrum with Galactic radius may partially account for the underprediction. A small medium-latitude (2° < |b| < 10°) excess in the direction of the inner Galaxy exists and may indicate that the low-energy photon density used in the model is too low.

Water Quality Functions of Riparian Forest Buffers in Chesapeake Bay Watersheds

Abstract: / Maryland, Virginia, and Pennsylvania, USA, have agreed to reduce nutrient loadings to Chesapeake Bay by 40% by the year 2000. This requires control of nonpoint sources of nutrients, much of which comes from agriculture. Riparian forest buffer systems (RFBS) provide effective control of nonpoint source (NPS) pollution in some types of agricultural watersheds. Control of NPS pollution is dependent on the type of pollutant and the hydrologic connection between pollution sources, the RFBS, and the stream. Water quality improvements are most likely in areas of where most of the excess precipitation moves across, in, or near the root zone of the RFBS. In areas such as the Inner Coastal Plain and Piedmont watersheds with thin soils, RFBS should retain 50%-90% of the total loading of nitrate in shallow groundwater, sediment in surface runoff, and total N in both surface runoff and groundwater. Retention of phosphorus is generally much less. In regions with deeper soils and/or greater regional groundwater recharge (such as parts of the Piedmont and the Valley and Ridge), RFBS water quality improvements are probably much less. The expected levels of pollutant control by RFBS are identified for each of nine physiographic provinces of the Chesapeake Bay Watershed. Issues related to of establishment, sustainability, and management are also discussed.KEY WORDS: Riparian forest buffers; Chesapeake Bay; Nonpoint source pollution; Nitrogen; Phosphorus; Sediment

The Impact of Aerosols on Solar Ultraviolet Radiation and Photochemical Smog

Abstract: Photochemical smog, or ground-level ozone, has been the most recalcitrant of air pollution problems, but reductions in emissions of sulfur and hydrocarbons may yield unanticipated benefits in air quality. While sulfate and some organic aerosol particles scatter solar radiation back into space and can cool Earth's surface, they also change the actinic flux of ultraviolet (UV) radiation. Observations and numerical models show that UV-scattering particles in the boundary layer accelerate photochemical reactions and smog production, but UV-absorbing aerosols such as mineral dust and soot inhibit smog production. Results could have major implications for the control of air pollution.

Do fair procedures matter? The effect of procedural justice on spouse assault.

Abstract: In a reanalysis of the Milwaukee Domestic Violence Experiment, the authors examine whether the use of fair procedures on the part of police officers called to the scene of a domestic assault inhibits subsequent assault. Consistent with expectations, they found that procedural justice did suppress subsequent violence, even in the face of adverse outcomes. When police acted in a procedurally fair manner when arresting assault suspects, the rate of subsequent domestic violence was significantly lower than when they did not. Moreover, suspects who were arrested and perceived that they were treated in a procedurally fair manner had subsequent assault rates that were as low as those suspects given a more favorable outcome (warned and then released without arrest). The suppression effect of procedural justice did not depend on the personal characteristics of suspects

Category and stereotype activation: Is prejudice inevitable?

Abstract: Three experiments tested the hypothesis that people high and low in prejudice respond similarly to direct stereotype activation but differently to category activation. Study 1 (N=40) showed that high- and low-prejudice people share the same knowledge of the stereotype of Black people. In Study 2, (N=51) high-prejudice participants formed a more negative and less positive impression of the target person after subliminal priming of the category Blacks than did participants in the no-prime condition. Low-prejudice people tended in the opposite direction. In Study 3 (N=45), both high- and low-prejudice people increased negative ratings when valenced stereotype content was also primed. These findings support a distinction between automatic stereotype activation resulting from direct priming and that consequent upon category activation, implying that the relations among categorization, stereotyping, and prejudice are more flexible than it is often assumed.

Ferroelectric Field Effect Transistor Based on Epitaxial Perovskite Heterostructures

Abstract: Ferroelectric field effect devices offer the possibility of nonvolatile active memory elements. Doped rare-earth manganates, which are usually associated with colossal magnetoresistive properties, have been used as the semiconductor channel material of a prototypical epitaxial field effect device. The carrier concentration of the semiconductor channel can be "tuned" by varying the manganate stochiometry. A device with La0.7Ca0.3MnO3 as the semiconductor and PbZr0.2Ti0.8O3 as the ferroelectric gate exhibited a modulation in channel conductance of at least a factor of 3 and a retention loss of 3 percent after 45 minutes without power.