Showing papers by "University of Rhode Island published in 2004"

Strengths of character and well-being

Abstract: We investigated the relationship between various character strengths and life satisfaction among 5,299 adults from three Internet samples using the Values in Action Inventory of Strengths. Consistently and robustly associated with life satisfaction were hope, zest, gratitude, love, and curiosity. Only weakly associated with life satisfaction, in contrast, were modesty and the intellectual strengths of appreciation of beauty, creativity, judgment, and love of learning. In general, the relationship between character strengths and life satisfaction was monotonic, indicating that excess on any one character strength does not diminish life satisfaction.

Distributions of Microbial Activities in Deep Subseafloor Sediments

Abstract: Diverse microbial communities and numerous energy-yielding activities occur in deeply buried sediments of the eastern Pacific Ocean. Distributions of metabolic activities often deviate from the standard model. Rates of activities, cell concentrations, and populations of cultured bacteria vary consistently from one subseafloor environment to another. Net rates of major activities principally rely on electron acceptors and electron donors from the photosynthetic surface world. At open-ocean sites, nitrate and oxygen are supplied to the deepest sedimentary communities through the underlying basaltic aquifer. In turn, these sedimentary communities may supply dissolved electron donors and nutrients to the underlying crustal biosphere.

The Role of Subjective Well-Being in Positive Youth Development

Abstract: Comprehensive perspectives on well-being that include positive aspects of human life such as subjective wellbeing have recently been proposed. Life satisfaction is the cognitive component of subjective well-being and plays an important role in positive development as an indicator, a predictor, a mediator/moderator, and an out-come. Whereas low life satisfaction is associated with psychological, social, and behavior problems, high life satisfaction is related to good adaptation and optimal mental health among youth. Life satisfaction and positive affect mitigate the negative effects of stressful life events and work against the development of psychological and behavioral problems among youth. Supportive parenting, engagement in challenging activities, positive life events, and high-quality interactions with significant others contribute to the development of life satisfaction. Further longitudinal research into the mechanisms of how life satisfaction plays its role in positive youth development is needed t...

Do parents still matter? Parent and peer influences on alcohol involvement among recent high school graduates.

Abstract: This study investigated the influences of peer and parent variables on alcohol use and problems in a sample of late adolescents in the summer immediately prior to entry into college. Participants (N = 556) completed a mail survey assessing peer influences (alcohol offers, social modeling, perceived norms), parental behaviors (nurturance, monitoring), and attitudes and values (disapproval for heavy drinking, permissiveness for drinking), and alcohol use and alcohol-related consequences. Hierarchical regression analyses indicated significant associations between both peer and parental influences and alcohol involvement, and showed that parental influences moderated peer-influence-drinking behavior, such that higher levels of perceived parental involvement were associated with weaker relations between peer influences and alcohol use and problems. These findings suggest that parents continue to exert an influential role in late adolescent drinking behavior.

Flying, fasting, and feeding in birds during migration: a nutritional and physiological ecology perspective

Abstract: Unlike exercising mammals, migratory birds fuel very high intensity exercise (e.g., flight) with fatty acids delivered from the adipose tissue to the working muscles by the circulatory system. Given the primary importance of fatty acids for fueling intense exercise, we discuss the likely limiting steps in lipid transport and oxidation for exercising birds and the ecological factors that affect the quality and quantity of fat stored in wild birds. Most stored lipids in migratory birds are comprised of three fatty acids (16:0, 18:1 and 18:2) even though migratory birds have diverse food habits. Diet selection and selective metabolism of lipids play important roles in determining the fatty acid composition of birds which, in turn, affects energetic performance during intense exercise. As such, migratory birds offer an intriguing model for studying the implications of lipid metabolism and obesity on exercise performance. We conclude with a discussion of the energetic costs of migratory flight and stopover in birds, and its implications for bird migration strategies.

Principles for modeling propensity scores in medical research: a systematic literature review

Abstract: Purpose To document which established criteria for logistic regression modeling researchers consider when using propensity scores in observational studies. Methods We performed a systematic review searching Medline and Science Citation to identify observational studies published in 2001 that addressed clinical questions using propensity score methods to adjust for treatment assignment. We abstracted aspects of propensity score model development (e.g. variable selection criteria, continuous variables included in correct functional form, interaction inclusion criteria), model discrimination and goodness of fit for 47 studies meeting inclusion criteria. Results We found few studies reporting on the propensity score model development or evaluation of model fit. Conclusions Reporting of aspects related to propensity score model development is limited and raises questions about the value of these principles in developing propensity scores from which unbiased treatment effects are estimated. Copyright © 2004 John Wiley & Sons, Ltd.

Analysis of the atmospheric distribution, sources, and sinks of oxygenated volatile organic chemicals based on measurements over the Pacific during TRACE‐P

Abstract: Airborne measurements of a large number of oxygenated volatile organic chemicals (OVOC) were carried out in the Pacific troposphere (0.1-12 km) in winter/spring of 2001 (24 February to 10 April). Specifically, these measurements included acetone (CH3COCH3), methylethyl ketone (CH3COC2H5, MEK), methanol (CH3OH), ethanol (C2H5OH), acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO), peroxyacylnitrates (PANs) (C(sub n)H(sub 2n+1)COO2NO2), and organic nitrates (C(sub n)H(sub 2n+1)ONO2). Complementary measurements of formaldehyde (HCHO), methyl hydroperoxide (CH3OOH), and selected tracers were also available. OVOC were abundant in the clean troposphere and were greatly enhanced in the outflow regions from Asia. Background mixing ratios were typically highest in the lower troposphere and declined toward the upper troposphere and the lowermost stratosphere. Their total abundance (Summation of OVOC) was nearly twice that of nonmethane hydrocarbons (Summation of C2-C8 NMHC). Throughout the troposphere, the OH reactivity of OVOC is comparable to that of methane and far exceeds that of NMHC. A comparison of these data with western Pacific observations collected some 7 years earlier (February-March 1994) did not reveal significant differences. Mixing ratios of OVOC were strongly correlated with each other as well as with tracers of fossil and biomass/biofuel combustion. Analysis of the relative enhancement of selected OVOC with respect to CH3Cl and CO in 12 plumes originating from fires and sampled in the free troposphere (3-11 km) is used to assess their primary and secondary emissions from biomass combustion. The composition of these plumes also indicates a large shift of reactive nitrogen into the PAN reservoir thereby limiting ozone formation. A three-dimensional global model that uses state of the art chemistry and source information is used to compare measured and simulated mixing ratios of selected OVOC. While there is reasonable agreement in many cases, measured aldehyde concentrations are significantly larger than predicted. At their observed levels, acetaldehyde mixing ratios are shown to be an important source of HCHO (and HO x ) and PAN in the troposphere. On the basis of presently known chemistry, measured mixing ratios of aldehydes and PANs are mutually incompatible. We provide rough estimates of the global sources of several OVOC and conclude that collectively these are extremely large (150-500 Tg C / yr) but remain poorly quantified.

Multiple Versus Single Antipsychotic Agents for Hospitalized Psychiatric Patients: Case-Control Study of Risks Versus Benefits

Abstract: Objective: Since use of multiple drugs to treat psychiatric patients is increasing, and research on this practice is rare, the authors carried out a retrospective case-control study of multiple versus single antipsychotic treatment in psychiatric inpatients. Method: Inpatient treatment groups receiving either antipsychotic monotherapy or polytherapy were matched in terms of age, sex, diagnostic category, and admission clinical ratings (Global Assessment of Functioning [GAF] and Clinical Global Impression [CGI]), which yielded 70 subject pairs. They were compared in terms of total chlorpromazine-equivalent daily dose, changes in total daily dose, length of hospitalization, incidence of adverse effects, and changes in clinical ratings (CGI, GAF, Positive and Negative Syndrome Scale score) between admission and discharge. Results: Initial doses were closely similar at admission for both treatment groups, but the median total final antipsychotic dose was 78% higher for those receiving antipsychotic polytherapy versus monotherapy. Also, median length of stay in the hospital was 55% (8.5 days) longer, and risk of adverse effects was 56% higher with polytherapy, whereas clinical improvement scores were similar (within 11%) for both treatments. Conclusions: Short-term treatment with multiple antipsychotics was associated with major increases in drug exposure, adverse events, and time in the hospital but with no apparent gain in clinical benefit. These findings require further testing in controlled prospective studies.

Character Strengths and Positive Youth Development

Abstract: The goal of positive youth development is to build and strengthen assets that enable youth to grow and flourish throughout life. In this article, the definition, origins, and assessment of character strengths and ways of fostering them are discussed. Character strengths are here defined as a family of positive traits reflected in thoughts, feelings, and behaviors. Character strengths are important in their own right, but they additionally promote well-being and buffer against psychological disorders among youth. Good parenting, close relationships with peer and family, positive role models, positive institutions, and various youth development programs play important roles in the development of character strengths. Character strengths exist in degrees, and they can be measured as individual differences. Future studies should approach character strengths as multidimensional constructs to understand better the structure and development of character, and how it contributes to positive youth development.

Image Reconstruction and Material Z Discrimination via Cosmic Ray Muon Radiography.

Abstract: Highly penetrating cosmic ray muons shower the Earth at the rate of 10,000 m −2 min −1 at sea level. In our previous work (Nature 422 (2003) 277; Rev. Sci. Instr. 74(10) (2003) 4294; Cosmic Ray Muon Radiography for Contraband Detection, in: Proceedings of AccApp’03, San Diego, CA, June 2003), we presented a novel muon radiography technique which exploits the multiple Coulomb scattering of these particles for nondestructive inspection without the use of artificial radiation. In this paper, we describe the concept of and theory behind cosmic ray muon radiography. We discuss the information carried by the scattered muons and our approaches for exploiting that information with image reconstruction algorithms. We discuss preliminary and advanced reconstruction algorithms, which take advantage of the scattering angle, scattering location, and locations where strongly scattered muons cross paths. Our algorithms are validated with both experimental demonstrations and Monte Carlo simulations. Based upon the results from both the experiment and simulations, we conclude that scattering muon radiography can be useful for both material discrimination and fast (minute order) detection of compact high- Z objects. Our ray-crossing algorithm, which highlights locations where strongly scattered muons cross paths, is effective even in the presence of a medium- Z background matrix.

Valanginian Weissert oceanic anoxic event

Abstract: Biotic changes in nannofossils and radiolarians associated with the Valanginian δ 1 3 C anomaly are documented at Ocean Drilling Program Hole 1149B in the Pacific Ocean: they are coeval and similar to those previously documented in the Tethys, suggesting a global perturbation of marine ecosystems. A marked increase in abundance of Diazomatolithus, absence of nannoconids, and a Pantanellium peak characterize the Valanginian δ 1 3 C excursion. Such changes are interpreted as being due to global enhanced fertility and a biocalcification crisis under conditions of excess CO 2 . The occurrence of organic C-rich black shales in the Southern Alps and in the Pacific in the interval corresponding to the δ 1 3 C excursion suggests a Valanginian oceanic anoxic event (OAE). Volcanism of the Parana-Etendeka large igneous province (ca. 132 Ma) was presumably responsible for an increase of CO 2 , triggering a climate change and accelerated hydrological cycling, possibly causing an indirect fertilization of the oceans. Widespread nutrification via introduction of biolimiting metals at spreading ridges could have significantly increased during the Gondwana breakup and simultaneous tectonic events in three separate oceans. There is no paleontological or δ 1 8 O evidence of warming during the Valanginian OAE. On the contrary, both nannofossils and oxygen isotopes record a cooling event at the climax of the δ 1 3 C excursion. Weathering of basalts and burial of organic C-rich black shales were presumably responsible for CO 2 drawdown and establishment of reversed greenhouse conditions.

“The Ball Was Always In His Court”: An Exploratory Analysis Of Relationship Scripts, Sexual Scripts, And Condom Use Among African American Women

Abstract: This qualitative study explored the association between African American women's interpersonal relationship and sexual scripts and condom use with primary partners. Participants were 14 lower to middle-income women between the ages of 22 and 39 involved in emotionally and sexually intimate heterosexual relationships. Relationship types included those that were: stable, emotionally committed; casual, primarily sexual; and unstable, emotionally imbalanced and/or conflict-ridden. Respondents completed a semi-structured interview and a questionnaire about their relationships, sexual, and condom use behaviors. Data analyses identified 3 interpersonal relationship scripts (i.e., men control relationships, women sustain relationships, infidelity is normative) and 2 interpersonal sexual scripts (i.e., men control sexual activity; women want to use condoms, but men control condom use) that may indirectly or directly decrease African American women's condom use with primary partners, and in turn increase their HIV risk. We discuss these interpersonal scripts within the context of sociocultural factors relevant to African American women, heterosexual relationships, and communities.

Propagation of the Great Salinity Anomaly of the 1990s around the northern North Atlantic

Abstract: [1] Time series of T and S extending through 2001 are used to describe propagation of the “Great Salinity Anomaly” of the 1990s (GSA'90s). Comparison of the distance-time relations for the GSA'70s, '80s, and '90s reveals a substantial intensification of the large-scale circulation in the northern North Atlantic, especially in the Subarctic Gyre between Newfoundland and the Faroes. The advection rate of the GSA'70s, '80s, and '90s between Newfoundland and the Faroe-Shetland Channel is conservatively estimated to have been 3.5, 10, and 10 cm/s, respectively. The circulation intensification apparently occurred within a decade between the GSA'70s and '80s. During the next decade the advection rate increased from 10 to 13 cm/s between Newfoundland and Iceland Basin. The GSA'90s was advected towards the Faroe-Shetland Channel by the northern (Iceland Basin's) branch of the North Atlantic Current, whereas the contribution of the southern branch via the Rockall Trough was minimal.

Multiple risk expert systems interventions: impact of simultaneous stage-matched expert system interventions for smoking, high-fat diet, and sun exposure in a population of parents.

Abstract: Three stage-based expert system interventions for smoking, high-fat diet, and unsafe sun exposure were evaluated in a sample of 2,460 parents of teenagers. Eighty-four percent of the eligible parents were enrolled in a 2-arm randomized control trial, with the treatment group receiving individualized feedback reports for each of their relevant behaviors at 0, 6, and 12 months as well as a multiple behavior manual. At 24 months, the expert system outperformed the comparison condition across all 3 risk behaviors, resulting in 22% of the participants in action or maintenance for smoking (vs. 16% for the comparison condition), 34% for diet (vs. 26%), and 30% for sun exposure (vs. 22%). Proactive, home-based, and stage-matched expert systems can produce significant multiple behavior changes in at-risk populations where the majority of participants are not prepared to change.

Near-Surface Turbulence in the Presence of Breaking Waves

Abstract: Observations with a three-axis pulse-to-pulse coherent acoustic Doppler profiler and acoustic resonators reveal the turbulence and bubble field beneath breaking waves in the open ocean at wind speeds up to 14 m s−1. About 55%–80% of velocity wavenumber spectra, calculated with Hilbert spectral analysis based on empirical mode decomposition, are consistent with an inertial subrange. Time series of turbulent kinetic energy dissipation at approximately 1 m beneath the free surface and 1-Hz sampling rate are obtained. High turbulence levels with dissipation rates more than four orders larger than the background dissipation are linked to wave breaking. Initial dissipation levels beneath breaking waves yield the Hinze scale of the maximum bubble size aH ≅ 2 × 10−3 m. Turbulence induced by discrete breaking events was observed to decay as e ∝ tn, where n = −4.3 is close to the theoretical value for isotropic turbulence (−17/4). In the crest region above the mean waterline, dissipation increases as e(z) ...

Real-Time Databases and Data Services

Abstract: Typically, a real–time system consists of a a controlling system and a controlled system. In an automated factory, the controlled system is the factory floor with its robots, assembling stations, and the assembled parts, while the controlling system is the computer and human interfaces that manage and coordinate the activities on the factory floor. Thus, the controlled system can be viewed as the environment with which the computer interacts. The controlling system interacts with its environment based on the data available about the environment, say from various sensors, e.g. temperature and pressure sensors. It is imperative that the state of the environment, as perceived by the controlling system, be consistent with the actual state of the environment. Otherwise, the effects of the controlling systems’ activities may be disastrous. Hence, timely monitoring of the environment as well as timely processing of the sensed information is necessary. The sensed data is processed further to derive new data. For example, the temperature and pressure information pertaining to a reaction may be used to derive the rate at which the reaction appears to be progressing. This derivation typically would depend on past temperature and pressure trends and so some of the needed information may have to be fetched from archival storage. Based on the derived data, where the derivation may involve multiple steps, actuator commands are set. For instance, in our example, the derived reaction rate is used to determine the amount of chemicals or coolant to be added to the reaction. In general, the history of (interactions with) the environment are also logged in archival storage. In addition to the timing constraints that arise from the need to continuously track the environment, timing correctness requirements in a real–time (database) system also arise because of the need to make data available to the controlling system for its decision-making activities. If the computer controlling a robot does not command it to stop or turn on time, the robot might collide with another object on the factory floor. Needless to say, such a mishap can result in a major catastrophe. Besides robotics, applications such as medical patient monitoring, programmed stock trading, and military command and control systems like submarine contact tracking require timely actions as well as the ability to access and store complex data that reflects the state of the application’s environment. That is, data in these applications must be valid, or fresh, when it is accessed in order for the application to perform correctly. In a patient monitoring system, data such as heart rate, temperature, and blood pressure must be collected periodically. Transactions that monitor the danger level of a patient’s status must be performed within a specified time, and the data must be accessed within an interval that defines the validity of the data. If not, the computations made by the transactions do not reflect the current state of the patient’s health. A traditional database provides some of the functionality required by these applications, such as coordination of concurrent actions and consistent access to shared data. But they do not provide for enforcement of the

The changing ecology of temperate coastal waters during a warming trend

Abstract: In the temperate North Atlantic Ocean the ecological changes in coastal waters associated with a warming period in the 1930s were compared with the past couple of decades when the North Atlantic Oscillation was also positive. Long-term monitoring data sets from Rhode Island and nearby coastal waters were used to identify trends in the recent warming period. During both events winter water temperatures warmed above a mean value of 2.9°C from 1°C to 3°C. There was no apparent trend in the annual salinity cycle correlated with the increased temperature. During both periods boreal species declined, southern species increased, and widespread declines in eelgrass occurred. Estuaries on the western Atlantic Ocean during the recent warming period had phytoplankton biomass during the winter-spring bloom decrease, zooplankton number increase, and nutrients remain elevated due to enhanced zooplankton grazing. Zooplankton numbers decreased in summer due to enhanced ctenophore predation. In these waters the loss of boreal demersal fish has been compensated by an increase in demersal decapods. The very large ecological changes caused by small increases in seasonal temperature provide an insight to the large alterations that may be associated with global warming.

A one hundred and seventeen year coastal water temperature record from Woods Hole, Massachusetts

Abstract: We have compiled what we believe is the longest coherent coastal sea surface temperature record in North America. Near-surface water temperature measurements have been made almost daily at Great Harbon, Woods Hole, Massachusetts, since 1886 with remarkably few gaps. The record shows that there was no significant trend in water temperature at this site for the first 60 yr of observation. There was some cooling during the 1960s that was followed by a significant warming from 1970–2002 at a rate of 0.04°C yr−1. During the 1990s annual mean temperatures averaged approximately 1.2°C warmer than they had been on average between 1890 and 1970; winter (December, January, and February) temperatures were 1.7°C warmer and summer (June, July, and August) temperatures were 1.0°C warmer. There has not been a statistically significant decrease in the annual number of winter days below 1°C or an increase in the annual number of winter days above 5°C. The number of summer days each year with water temperature above 21°C has not increased significantly. The dates of first observations of 10°C and 20°C water in the spring have not changed sufficiently to be statistically significant. There is a weak positive correlation between annual and winter water temperature and the annual and winter North Atlantic Oscillation index, respectively, during the period of record.

Effect of Surface Waves on Air–Sea Momentum Exchange. Part II: Behavior of Drag Coefficient under Tropical Cyclones

Abstract: Present parameterizations of air–sea momentum flux at high wind speed, including hurricane wind forcing, are based on extrapolation from field measurements in much weaker wind regimes. They predict monotonic increase of drag coefficient (Cd) with wind speed. Under hurricane wind forcing, the present numerical experiments using a coupled ocean wave and wave boundary layer model show that Cd at extreme wind speeds strongly depends on the wave field. Higher, longer, and more developed waves in the right-front quadrant of the storm produce higher sea drag; lower, shorter, and younger waves in the rear-left quadrant produce lower sea drag. Hurricane intensity, translation speed, as well as the asymmetry of wind forcing are major factors that determine the spatial distribution of Cd. At high winds above 30 m s−1, the present model predicts a significant reduction of Cd and an overall tendency to level off and even decrease with wind speed. This tendency is consistent with recent observational, experime...

Suppression of Toxic Compounds Produced in the Decomposition of Lithium-Ion Battery Electrolytes

Abstract: Liquid electrolytes typically used in commercial lithium-ion batteries are comprised of lithium hexafluorophosphate in carbonate solvents. This electrolyte undergoes thermal decomposition at moderately elevated temperatures (80-100°C), encountered in the normal operation of these rechargeable power sources, to quantitatively generate highly toxic alkylfluorophosphates. The decomposition occurs via an autocatalytic mechanism initiated by trace impurities of water or alcohol. The thermal decomposition is inhibited in the presence of lithium metal oxides frequently used as the cathode of lithium-ion batteries or Lewis basic additives.

Air‐sea gas transfer: Its dependence on wind stress, small‐scale roughness, and surface films

Abstract: [1] The influence of wind stress, small-scale waves, and surface films on air-sea gas exchange at low to moderate wind speeds (<10 m s−1) is examined. Coincident observations of wind stress, heat transfer velocity, surface wave slope, and surface film enrichments were made in coastal and offshore waters south of Cape Cod, New England, in July 1997 as part of the NSF-CoOP Coastal Air-Sea Chemical Fluxes study. Gas transfer velocities have been extrapolated from aqueous heat transfer velocities derived from infrared imagery and direct covariance and bulk heat flux estimates. Gas transfer velocity is found to follow a quadratic relationship with wind speed, which accounts for ∼75–77% of the variance but which overpredicts transfer velocity in the presence of surface films. The dependence on wind stress as represented by the friction velocity is also nonlinear, reflecting a wave field-dependent transition between limiting transport regimes. In contrast, the dependence on mean square slope computed for the wave number range of 40–800 rad m−1 is found to be linear and in agreement with results from previous laboratory wind wave studies. The slope spectrum of the small-scale waves and the gas transfer velocity are attenuated in the presence of surface films. Observations over large-scale gradients of biological productivity and dissolved organic matter show that the reduction in slope and transfer velocity are more clearly correlated with surface film enrichments than with bulk organic matter concentrations. The mean square slope parameterization explains ∼89–95% of the observed variance in the data and does not overpredict transfer velocities where films are present. While the specific relationships between gas transfer velocity and wind speed or mean square slope vary slightly with the choice of Schmidt number exponent used to scale the heat transfer velocities to gas transfer velocities, the correlation of heat or gas transfer velocity with mean square slope is consistently better than with wind speed.

Whose Identity Is It Anyway? Consumer Representation in the Age of Database Marketing

Abstract: In the information-intensive marketplaces of the networked economy, database-related marketing techniques have gained unprecedented popularity. Their development is based on the assumption that greater capturing of customer information in digital databases leads to epistemologically superior insights about the customer. The proliferation of customer databases, however, has triggered privacy concerns and has encouraged consumers to devise information externalization strategies to maintain control over their digital representation (identity) vis-a-vis companies. Drawing on poststructuralist theory, the authors argue that current consumer strategies are ineffective in maintaining control over one’s identity in the electronic marketplace because such strategies are based on an obsolete ontological distinction between material identity and digital representation. They suggest that in the age of database marketing, digital consumer representations in fact constitute the consumer. Therefore, only if consumers ar...

Strengths of character and well-being: A closer look at hope and modesty

Abstract: We took a closer look at the link between character strengths and well-being by following up on suggestions by Snyder (this issue) and Harvey and Pauwels (this issue). We explored the simultaneous association between 24 strengths of character and life satisfaction and found that a number of different strengths independently predicted life satisfaction. Hope was among the important predictors, as Snyder proposed, but it was no more robust a predictor than the character strengths of gratitude, love, and zest. We also found that trauma moderated the association between modesty and well-being, as Harvey and Pauwels hypothesized. With increasing trauma, the correlation between modesty and enthusiasm about life increased in magnitude. These new analyses further our comparative investigation of character strengths and imply that there are different routes to a satisfied life.

Glycolytic and Gluconeogenic Growth of Escherichia coli O157:H7 (EDL933) and E. coli K-12 (MG1655) in the Mouse Intestine

Abstract: Escherichia coli EDL933, an O157:H7 strain, is known to colonize the streptomycin-treated CD-1 mouse intestine by growing in intestinal mucus (E. A. Wadolkowski, J. A. Burris, and A. D. O'Brien, Infect. Immun. 58:2438-2445, 1990), but what nutrients and metabolic pathways are employed during colonization has not been determined. In this study, when the wild-type EDL933 strain was fed to mice along with an EDL933 DeltappsA DeltapckA mutant, which is unable to utilize tricarboxylic acid cycle intermediates and gluconeogenic substrates for growth, both strains colonized the mouse intestine equally well. Therefore, EDL933 utilizes a glycolytic substrate(s) for both initial growth and maintenance when it is the only E. coli strain fed to the mice. However, in the presence of large numbers of MG1655, a K-12 strain, it is shown that EDL933 utilizes a glycolytic substrate(s) for initial growth in the mouse intestine but appears to utilize both glycolytic and gluconeogenic substrates in an attempt to maintain colonization. It is further shown that MG1655 predominantly utilizes glycolytic substrates for growth in the mouse intestine whether growing in the presence or absence of large numbers of EDL933. Data are presented showing that although small numbers of EDL933 grow to large numbers in the intestine in the presence of large numbers of MG1655 when both strains are fed to mice simultaneously, precolonization with MG1655 affords protection against subsequent colonization by EDL933. Moreover, in mice that are precolonized with EDL933, small numbers of MG1655 are able to grow rapidly in the intestine and EDL933 is eliminated. In situ hybridization experiments using E. coli-specific rRNA probes showed that while MG1655 is found only in mucus, EDL933 is found both in mucus and closely associated with intestinal epithelial cells. The data are discussed with respect to competition for nutrients and to the protection that some intestinal commensal E. coli strains might afford against infection by O157:H7 strains.

Within-pond parameters affecting oviposition by wood frogs and spotted salamanders

Abstract: Previous research on habitat associations of pond-breeding amphibians has used community assemblages as response variables because the intensive labor required to quantify population size is usually prohibitive. However, wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum) oviposit egg masses that can be surveyed rapidly; thus, we were able to quantify the influence of within-pond parameters on their annual breeding effort. During 2000–2001, we assessed the effects of hydroperiod, within-pond vegetation, canopy closure, hydrologic isolation, fish occurrence, and pond size on egg mass counts of wood frogs and spotted salamanders at 124 ponds in western Rhode Island. Study sites were stratified by road density, which served as an indirect measure of non-breeding habitat quality and quantity. Hydroperiod had a significant influence on annual breeding effort. Egg masses of both species were most abundant in seasonal ponds that dried between 1 August and 30 November. Breeding populations of spotted salamanders were smaller in ponds that dried before the end of July, whereas breeding populations of wood frogs were reduced in ponds that did not dry during our two-year study. Both species usually attached egg masses to shrubs or branches in shallow water near the water surface, which may explain why both species oviposited more egg masses in ponds with substantial vegetation complexity, including extensive coverage by shrubs and persistent non-woody vegetation. Although wood frogs were more likely than spotted salamanders to avoid ovipositing in ponds with fish, egg mass counts of both species were substantially reduced in ponds containing fish. Numbers of egg masses for spotted salamanders and wood frogs were similar between larger ponds and those as small as 0.05 ha and 0.15 ha, respectively. Previously, researchers proposed protecting isolated wetlands > 0.2 ha to sustain populations of pond-breeding amphibians, but our research suggests that wetlands as small as 0.05 ha may provide critical breeding habitat for some species in southern New England.