Showing papers by "University of Rhode Island published in 1996"

The fate of nitrogen and phosphorus at the land-sea margin of the North Atlantic Ocean

Abstract: Five large rivers that discharge on the western North Atlantic continental shelf carry about 45% of the nitrogen (N) and 70% of the phosphorus (P) that others estimate to be the total flux of these elements from the entire North Atlantic watershed, including North, Central and South America, Europe, and Northwest Africa. We estimate that 61 · 109 moles y-1 of N and 20 · 109 moles y-1 of P from the large rivers are buried with sediments in their deltas, and that an equal amount of N and P from the large rivers is lost to the shelf through burial of river sediments that are deposited directly on the continental slope. The effective transport of active N and P from land to the shelf through the very large rivers is thus reduced to 292 · 109 moles y-1 of N and 13 · 109 moles y-1 of P.

Tracking control of a piezoceramic actuator

Abstract: The tracking control accuracy of piezoceramic actuators is limited due to their inherent hysteresis nonlinearity. This paper presents a computer-based tracking control approach for a piezoceramic actuator based on incorporating a feedforward loop with a PID (proportional-integral-derivative) feedback controller. The hysteresis nonlinearity of the piezoceramic actuator is modeled in the feedforward loop by using the classical Preisach model. Experiments were performed on a stacked piezoceramic actuator for tracking sinusoidal waveforms with signal frequencies ranging from 0.1-20 Hz. A comparison was made between a feedforward control scheme, a regular PID feedback control scheme, and a PID feedback control scheme with hysteresis modeling in the feedforward loop. The results show that the tracking control performance is greatly improved by augmenting the feedback loop with a model of hysteresis in the feedforward loop. The maximum error in tracking a sinusoidal waveform is about half that obtained using a regular PID controller.

Intercultural Communication Competence: A Synthesis

Abstract: As we encounter ever greater cultural and co-cultural diversity, the careful study of intercultural communication competence becomes increasingly important. Only through competent intercultural communication can persons from different cultures communicate effectively and appropriately in the upcoming global society. Following a recounting of themes of research on intercultural communication, this chapter presents arguments concerning individuals’ need to negotiate multiple identities in terms of culture, race, ethnicity, gender, and religion in the interdependent and interconnected network of global society. This requires a functional and theoretical transformation of the study of intercultural communication competence.

A meta-analysis of predictors of postpartum depression

Abstract: A meta-analysis of 44 studies was conducted to determine the magnitude of the relationship between postpartum depression and each of the following predictor variables: prenatal depression, history of previous depression, social support, life stress, child care stress, maternity blues, marital satisfaction, and prenatal anxiety. Effect sizes were calculated three ways: unweighted, weighted by sample size, and weighted by quality index score. Moderate to large significant effect sizes were revealed between these eight predictor variables and postpartum depression. The mean r effect size indicator range for each predictor variable was as follows: prenatal depression (.49 to .51), child care stress (.48 to .49), life stress (.36 to .40), social support (.37 to .39), prenatal anxiety (.30 to .36), maternity blues (.35 to .37), marital satisfaction (.29 to .37), and history of previous depression (.27 to .29).

Controlled-Release Drug Delivery Systems for Prolonged Gastric Residence: An Overview

Abstract: (1996). Controlled-Release Drug Delivery Systems for Prolonged Gastric Residence: An Overview. Drug Development and Industrial Pharmacy: Vol. 22, No. 6, pp. 531-539.

Origin of ozone and NOx in the tropical troposphere: A photochemical analysis of aircraft observations over the South Atlantic basin

Abstract: The photochemistry of the troposphere over the South Atlantic basin is examined by modeling of aircraft observations up to 12-km altitude taken during the TRACE A expedition in September–October 1992. A close balance is found in the 0 to 12-km column between photochemical production and loss of O3, with net production at high altitudes compensating for weak net loss at low altitudes. This balance implies that O3 concentrations in the 0–12 km column can be explained solely by in situ photochemistry; influx from the stratosphere is negligible. Simulation of H2O2, CH3OOH, and CH2O concentrations measured aboard the aircraft lends confidence in the computations of O3 production and loss rates, although there appears to be a major gap in current understanding of CH2O chemistry in the marine boundary layer. The primary sources of NOx over the South Atlantic Basin appear to be continental (biomass burning, lightning, soils). There is evidence that NOx throughout the 0 to 12-km column is recycled from its oxidation products rather than directly transported from its primary sources. There is also evidence for rapid conversion of HNO3 to NOx in the upper troposphere by a mechanism not included in current models. A general representation of the O3 budget in the tropical troposphere is proposed that couples the large-scale Walker circulation and in situ photochemistry. Deep convection in the rising branches of the Walker circulation injects NOx from combustion, soils, and lightning to the upper troposphere, leading to O3 production; eventually, the air subsides and net O3 loss takes place in the lower troposphere, closing the O3 cycle. This scheme implies a great sensitivity of the oxidizing power of the atmosphere to NOx emissions in the tropics.

Rapid Variations in Atmospheric Methane Concentration During the Past 110,000 Years

Abstract: A methane record from the GISP2 ice core reveals that millennial-scale variations in atmospheric methane concentration characterized much of the past 110,00 years. As previously observed in a shorter record from central Greenland, abrupt concentration shifts of about 50 to 300 parts per billion by volume were coeval with most of the interstadial warming events (better known as Dansgaard-Oeschger events) recorded in the GISP2 ice core throughout the last glacial period. The magnitude of the rapid concentration shifts varied on a longer time scale in a manner consistent with variations in Northern Hemisphere summer insolation, which suggests that insolation may have modulated the effects of interstadial climate change on the terrestrial biosphere.

A simple and rapid solvent extraction method for determining total lipids in fish tissue

Abstract: Solvent systems that have been developed for lipid extraction include chloroform-methanol, n-hexane-isopropyl alcohol, and methylene chloride-methanol. The extraction methods are labor intensive, lack precision, or require a large volume of solvent. Correct computation of lipid content calls for full recovery of solvent after extraction, but recovery always is incomplete because of unaccounted solvent residue that remains in jar, filter paper, and homogenized tissue. A rapid and simple extraction method coupled with correct computation was developed for determining total lipids in fish tissue. The method uses chloroform-methanol and an Eberbach blending jar. Variables examined were chloroform-methanol ratio, solvent-to-sample ratio, and phase separation time. Precision was within 0.5%. Conventional computation of lipid content depends on the volume of chloroform measured after filtration. This volume does not include unaccounted solvent residue. Thus, a time-consuming second extraction is required for complete recovery. The mass balance of each extraction and filtration step confirmed that the correct volume of chloroform (measured plus unaccounted) was close to the theoretical volume. The procedure eliminates problems associated with laborious filtration and variation in chloroform volume readings and does not require an exact reading of chloroform volume. Instead it allows use of a theoretical volume, which depends on solvent volume and ratio used.

Marine Reserves for Fisheries Management

Abstract: Conventional methods of regulating commercial fisheries restrict catch by limiting either the quantity or efficiency of fishing effort, or by putting direct limits on catch. These regulatory practices are neither feasible nor desirable for many fisheries, and have failed to conserve fishery stocks in other fisheries. Marine reserves may be an effective alternative management strategy for some fisheries. Here we develop a dynamic model of marine reserves applicable to inshore fisheries. In contrast to previous models of reserves, the model is fully dynamic and provides information on both equilibrium conditions and the path to equilibrium. A simulation model based on red snapper data from the Gulf of Mexico is presented. The simulation results suggest that marine reserves can sustain or increase yields for moderate to heavily fished fisheries but will probably not improve yields for lightly fished fisheries.

Atmospheric gas concentrations over the past century measured in air from firn at the South Pole

Abstract: The extraction and analysis of air from the snowpack (firn) at the South Pole provides atmospheric concentration histories of biogenic greenhouse gases since the beginning of the present century which confirm and expand on those derived from studies of air trapped in ice cores. Furthermore, calculations based on the inferred atmospheric concentrations of oxygen and carbon dioxide indicate that–in contrast to the past few years—the terrestrial biosphere was neither a source nor sink of C02 between ˜1977 and 1985.

Chemical aspects of tool wear in single point diamond turning

Abstract: A hypothesis is proposed that ascribes chemical wear of diamond tools to the presence of unpaired d electrons in the sample being machined. This hypothesis is used to explain a range of results for metals, alloys, and other materials including “electroless” nickel. The hypothesis is further tested by experiments presented here on the machining of a range of high purity elements. The implications for diamond turnability of other materials are discussed.

Integrating individual and public health perspectives for treatment of tobacco dependence under managed health care: A combined stepped-care and matching model

Abstract: There is an increasing momentum to integrate prevention into mainstream health care. Three decades of research on tobacco dependence can provide insights into the conceptual, clinical, economic, and service delivery challenges to such an integration. Biological sciences, cognitive-behavioral, clinical treatment outcome, and public health arenas are selectively reviewed. The key conceptual issues are explored relevant to the optimal delivery of quality smoking cessation treatments for the general population of adult smokers at reasonable cost. A comprehensive model for adult smoking cessation treatment is developed. The model consists of an overarching public health approach, focusing on enhancing motivational level from low motivation to quit to high motivation. A common outcome metric of overall impact is proposed to facilitate comparisons between clinical and public health interventions. Smokers are then assessed and triaged into one of three treatment steps of minimal, moderate, and maximal intensity and cost. Smoker individual differences at both the population and individual level are also taken into account as part of a tailoring or matching strategy within and across the stepped interventions. Smoker profiles include sociocultural, nicotine dependence, and comorbidity factors. The result is a hybrid stepped-care matching model. The model serves to illustrate some of the needs and challenges facing future tobacco dependence research and practice. Comparisons are made between tobacco control and other preventive medicine practices in terms of cost per quality adjusted life-year saved. The barriers and opportunities under managed care are explored. The conceptual principles identified here could be used as a guidepost for integrating other preventive medicine programs into the evolving managed health care system.

Convective transport of biomass burning emissions over Brazil during TRACE A

Abstract: A series of large mesoscale convective systems that occurred during the Brazilian phase of GTE/TRACE A (Transport and Atmospheric Chemistry near the Equator-Atlantic) provided an opportunity to observe deep convective transport of trace gases from biomass burning. This paper reports a detailed analysis of flight 6, on September 27, 1992, which sampled cloud- and biomass-burning-perturbed regions north of Brasilia. High-frequency sampling of cloud outflow at 9-12 km from the NASA DC-8 showed enhancement of CO mixing ratios typically a factor of 3 above background (200- 300 parts per billion by volume (ppbv) versus 90 ppbv) and significant increases in NOx and hydrocarbons. Clear signals of lightning-generated NO were detected; we estimate that at least 40% of NO x at the 9.5-km level and 32% at 11.3 km originated from lightning. Four types of model studies have been performed to analyze the dynamical and photochemical characteristics of the series of convective events. (1) Regional simulations for the period have been performed with the NCAR/Penn State mesoscale model (MM5), including tracer transport of carbon monoxide, initialized with observations. Middle-upper tropospheric enhancements of a factor of 3 above background are reproduced. (2) A cloud-resolving model (the Goddard cumulus ensemble (GCE) model) has been run for one representative convective cell during the September 26-27 episode. (3) Photochemical calculations (the Goddard tropospheric chemical model), initialized with trace gas observations (e.g., CO, NO x, hydrocarbons, 03) observed in cloud outflow, show appreciable 0 3 formation postconvection, initially up to 7-8 ppbv O3/d. (4) Forward trajectories from cloud outflow levels (postconvective conditions) put the ozone-producing air masses in eastern Brazil and the tropical Atlantic within 2-4 days and over the Atlantic, Africa, and the Indian Ocean in 6-8 days. Indeed, 3-4 days after the convective episode (September 30, 1992), upper tropospheric levels in the Natal ozone sounding show an average increase of -30 ppbv (3 Dobson units (DU) integrated) compared to the September 28 sounding. Our simulated net 0 3 production rates in cloud outflow are a factor of 3 or more greater than those in air undisturbed by the storms. Integrated over the 8- to 16-km cloud outflow layer, the postconvection net 0 3 production (-5-6 DU over 8 days) accounts for -25% of the excess 03 (15-25 DU) over the South Atlantic. Comparison of TRACE A Brazilian ozonesondes and the frequency of deep convection with climatology (Kirchhoff et al., this issue) suggests that the late September 1992 conditions represented an unusually active period for both convection and upper tropospheric ozone formation.

MICROALGAL METABOLITES: A New Perspective

Abstract: Occurrence of secondary metabolites in microalgae (protoctista) is discussed with respect to the phylogenic or taxonomic relationships of organisms. Biosynthetic mechanisms of certain metabolites such as paralytic shellfish poisoning toxins and polyether toxins are also discussed, and genetic aspects of the secondary metabolite production as well.

Volcanic growth faults and the origin of Pacific abyssal hills

Abstract: The topographic features known as abyssal hills characterize >30% of the ocean floor, and yet their origin has been the subject of vigorous debate for over 40 years. Submersible-based investigations show that Pacific abyssal hills are created on the flanks of the East Pacific Rise as horsts and grabens which lengthen with time. Hills are bounded on one side by ridge-facing scarps produced by normal faulting, and on the other by more gentle slopes produced by volcanic growth faulting.

Henry's Law Constant Determinations for Hydrogen Peroxide, Methyl Hydroperoxide, Hydroxymethyl Hydroperoxide, Ethyl Hydroperoxide, and Peroxyacetic Acid

Abstract: The temperature-dependent solubilities of hydrogen peroxide (H2O2), hydroxymethyl hydroperoxide (HOCH2O2H), methyl hydroperoxide (CH3O2H), peroxyacetic acid (CH3C(O)O2H), and ethyl hydroperoxide (C2H5O2H) were determined under conditions used in the aqueous collection and analysis of atmospheric hydroperoxides. Henry's law was obeyed over the source concentration range employed, nominally 10-6−10-2 M. Measurements were made using either pH = 3 or pH = 6 source and collection solutions. The temperatures investigated ranged from 4 to 28 °C. A solution pH 3 was used for experiments with H2O2, HOCH2O2H, and CH3C(O)O2H since these compounds decompose in less acidic solution. The solubility of HOC2H4O2H could not be accurately determined because of its rapid decomposition in solutions with pH > 3. The Henry's law solubility of H2O2, HOCH2O2H, CH3O2H, and CH3C(O)O2H are in agreement with prior determinations. The solubility measurement of C2H5O2H is the first of its kind. Dimensional Henry's law constants (M/atm...

Climatic interpretation of the recently extended Vostok ice records

Abstract: A new ice core drilled at the Russian station of Vostok in Antarctica reached 2755 m depth in September 1993. At this depth, the glaciological time scale provides an age of 260 ky BP (±25). We refine this estimate using records of dust and deuterium in the ice and of δ18O of O2 in the entrapped air. δ18O of O2 is highly correlated with insolation over the last two climatic cycles if one assumes that the EGT chronology overestimates the increase of age with depth by 12% for ages older than 112 ky BP. This modified age-depth scale gives an age of 244 ky BP at 2755 m depth and agrees well with the age-depth scale of Walbroeck et al. (in press) derived by orbital tuning of the Vostok δD record. We discuss the temperature interpretation of this latter record accounting for the influence of the origin of the ice and using information derived from deuterium-excess data. We conclude that the warmest period of stage 7 was likely as warm as today in Antarctica. A remarkable feature of the Vostok record is the high level of similarity of proxy temperature records for the last two climatic cycles (stages 6 and 7 versus stages 1–5). This similarity has no equivalent in other paleorecords.

Entomologic Index for Human Risk of Lyme Disease

Abstract: An entomologic index based on density estimates of Lyme disease spirochete-infected nymphal deer ticks (lxodes scapularis) was developed to assess human risk of Lyme disease. The authors used a standardized protocol to determine tick density and infection in numerous forested sites in six Rhode Island towns. An entomologic risk index calculated for each town was compared with the number of human Lyme disease cases reported to the Rhode Island State Health Department for the same year. A strong positive relation between entomologic risk index and the Lyme disease case rate for each town suggested that the entomologic index was predictive of Lyme disease risk.

Methods for Evaluating Lyme Disease Risks Using Geographic Information Systems and Geospatial Analysis

Abstract: Lyme disease is a tick-transmitted borreliosis of humans and domestic animals emerging as one of the most significant threats to public health in north temperate regions of the world. However, despite a myriad of studies into symptomology, causes, and treatment of the disease, few researchers have addressed the spatial aspects of Lyme disease transmission. Using statewide data collected in Rhode Island (United States) as a test case, we demonstrated that exposure to deer ticks and the risk of contracting Lyme disease occurs mostly in the peridomestic environment. A Geographic Information System model was developed indicating a strong association among Lyme disease in humans, the degree of nymphal blacklegged tick, Ixodes scapularis Say, abundance in the environment, and prevalence of Borrelia burgdorferi infection in ticks. In contrast, occurrence of plant communities suitable for sustaining I. scapularis populations (forests) was not predictive of Lyme disease risk. Instead, we observed a highly significant spatial trend for decreasing number of ticks and incident cases of Lyme disease with increasing latitude. Geostatistics were employed for modeling spatial autocorrelation of tick densities. These findings were combined to create a model that predicts Lyme disease transmission risk, thereby demonstrating the utility of incorporating geospatial modeling techniques in studying the epidemiology of Lyme disease.

Postpartum depressed mothers' experiences interacting with their children.

Abstract: A phenomenological study was conducted to investigate the meaning of postpartum depressed mothers' interactions with their infants and older children. A purposive sample of 12 mothers participated. Nine theme clusters emerged when the formulated meaning were organized into categories. Participants were overwhelmed by the responsibilities of caring for their children. Guilt, irrational thinking, loss and anger filled their day-to-day interactions with their children. Mothers went through the motions, acting like robots while caring for their infants. At times, to survive, they erected a wall to separate themselves emotionally from their children and consequently failed to respond to their infants' cues. Detrimental relationships with their older children materialized as mothers were enveloped by postpartum depression.

DCD --- Disk Caching Disk: A New Approach for Boosting I/O Performance

Abstract: This paper presents a novel disk storage architecture called DCD, Disk Caching Disk, for the purpose of optimizing I/O performance. The main idea of the DCD is to use a small log disk, referred to as cache-disk, as a secondary disk cache to optimize write performance. While the cache-disk and the normal data disk have the same physical properties, the access speed of the former differs dramatically from the latter because of different data units and different ways in which data are accessed. Our objective is to exploit this speed difference by using the log disk as a cache to build a reliable and smooth disk hierarchy. A small RAM buffer is used to collect small write requests to form a log which is transferred onto the cache-disk whenever the cache-disk is idle. Because of the temporal locality that exists in office/engineering work-load environments, the DCD system shows write performance close to the same size RAM (i.e. solid-state disk) for the cost of a disk. Moreover, the cache-disk can also be implemented as a logical disk in which case a small portion of the normal data disk is used as the log disk. Trace-driven simulation experiments are carried out to evaluate the performance of the proposed disk architecture. Under the office/engineering work-load environment, the DCD shows superb disk performance for writes as compared to existing disk systems. Performance improvements of up to two orders of magnitude are observed in terms of average response time for write operations. Furthermore, DCD is very reliable and works at the device or device driver level. As a result, it can be applied directly to current file systems without the need of changing the operating system.

Wind-induced Kuroshio intrusion into the South China Sea

Abstract: The Kuroshio flows north along the east coasts of the Philippines and Taiwan. Between these two land masses lies the Luzon Strait which connects the Pacific Ocean to the South China Sea. The Kuroshio usually flows north past this strait, but at times part or all of it flows west through the strait into the South China Sea forming a loop current. It has been suggested that the loop current forms when the northeast monsoon deflects the Kuroshio through the Luzon Strait. In this study, satellite-derived sea-surface temperature images are used to observe the Kuroshio in the Luzon Strait region. Together with wind data from the region, these observations indicate a loop-current development process which is largely determined by an integrated supercritical wind stress parameter. The loop current grows when a four-day average of the local wind-stress component directed to the south exceeds 0.08 Nm−2. When this average wind-stress component drops below the critical value, the Kuroshio returns to its northward path.