Nitrogen sources to watersheds and estuaries: role of land cover mosaics and losses within watersheds.

Across most of the World's coastal zone there has been a geographic transition from naturally vegetated to human-altered land covers, both agricultural and urban. This transition has increased the nitrogen loads to coastal watersheds, and from watersheds to receiving estuaries. We modeled the nitrogen entering the watershed of Waquoit Bay, Massachusetts, and found that as the transition took place, nitrogen loads to watersheds increased from 1938 to 1990. The relative magnitude of the contribution by wastewater, fertilizers, and atmospheric deposition depends on the land cover mosaics of a watershed. Atmospheric deposition was the major input to the watershed surface during this period, but because of different rates of loss within the watershed. wastewater became the major source of nitrogen flowing from the watershed to the receiving estuaries. Atmospheric deposition prevails in watersheds dominated by natural vegetation such as forests, but wastewater may become a dominant source in watersheds where urbanization increases. Increased nitrogen loads resulting from conversion of natural to human-altered watershed surfaces create eutrophication of receiving waters, with attendant changes in water quality, and marked shifts in the flora and food webs of the affected estuaries. Management efforts for restoration of eutrophied estuaries require maintenance of forested land, and control of wastewater and fertilizer inputs, the major terms in most affected places subject to local management. Wastewater and fertilizer nitrogen derive from within the watershed, which means local measures may effectively be used to control eutrophication of receiving waters.

Time-resolved characterization of diesel particulate emissions. 2. Instruments for elemental and organic carbon measurements.

The measurement of elemental carbon (EC) and organic carbon (OC) mass for particles emitted by diesel vehicles is currently accomplished using particle collection on filters, followed by analysis using the thermal/optical reflectance carbon analysis method (TOR) or one of its variations. Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Testing of five different measurement methods has demonstrated that fast response measurement of diesel exhaust particulate EC and OC concentrations, consistent with TOR filter measurements, is feasible using existing technology. EC mass concentrations are best measured through determination of particulate light absorption with a photoacoustic instrument or determination of light extinction with a smoke meter. The photoacoustic instrument has the better dynamic range and sensitivity, whereas the smoke meter is a simpler instrument. Fast response OC measurements cannot be made with any single instrument tested. However, a combination of real time weighing as implemented in the tapered element oscillating microbalance with the photoacoustic instrument has been shown to be capable of determining OC concentrations with good time response. The addition of a nephelometer to the OC measurement could potentially improve time resolution, freedom from interferences, and sensitivity.

Time resolved characterization of diesel particulate emissions. 1. Instruments for particle mass measurements.

The measurement of diesel vehicle exhaust particulate mass is currently accomplished using filter collection methods according to the Code of Federal Regulations (CFR). Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Extensive testing of five different measurement methods has demonstrated that fast response measurements of diesel exhaust particulate mass concentrations, consistent with CFR filter measurements, are feasible using existing technology. The measurement principles of choice are the real time weighing of exhaust samples as implemented in the tapered element oscillating microbalance (TEOM) and the measurement of light scattering from exhaust particles as implemented in the DustTrak nephelometer. Each of these two instruments has distinctive strengths. The TEOM excels in the area of constant calibration, independent of vehicle. For the DustTrak, this calibration varies by vehicle. On the other hand, the DustTrak has an excellent signal-to-noise ratio, freedom from interference due to other exhaust sample properties, good time resolution, and simplicity. The strengths of the two measurement methods are complimentary, so an obvious suggestion is to integrate them. The nephelometer would obtain a fast response signal, with near real time calibration provided by the microbalance.

Air quality measurements from the Fresno Supersite.

The Fresno Supersite intends to 1) evaluate non-routine monitoring methods, establishing their comparability with existing methods and their applicability to air quality planning, exposure assessment, and health effects studies; 2) provide a better understanding of aerosol characteristics, behavior, and sources to assist regulatory agencies in developing standards and strategies that protect public health; and 3) support studies that evaluate relationships between aerosol properties, co-factors, and observed health end-points. Supersite observables include in-situ, continuous, short-duration measurements of 1) PM2.5, PM10, and coarse (PM10 minus PM2.5) mass; 2) PM2.5 SO4(-2), NO3-, carbon, light absorption, and light extinction; 3) numbers of particles in discrete size bins ranging from 0.01 to approximately 10 microns; 4) criteria pollutant gases (O3, CO, NOx); 5) reactive gases (NO2, NOy, HNO3, peroxyacetyl nitrate [PAN], NH3); and 6) single particle characterization by time-of-flight mass spectrometry. Field sampling and laboratory analysis are applied for gaseous and particulate organic compounds (light hydrocarbons, heavy hydrocarbons, carbonyls, polycyclic aromatic hydrocarbons [PAH], and other semi-volatiles), and PM2.5 mass, elements, ions, and carbon. Observables common to other Supersites are 1) daily PM2.5 24-hr average mass with Federal Reference Method (FRM) samplers; 2) continuous hourly and 5-min average PM2.5 and PM10 mass with beta attenuation monitors (BAM) and tapered element oscillating microbalances (TEOM); 3) PM2.5 chemical speciation with a U.S. Environmental Protection Agency (EPA) speciation monitor and protocol; 4) coarse particle mass by dichotomous sampler and difference between PM10 and PM2.5 BAM and TEOM measurements; 5) coarse particle chemical composition; and 6) high sensitivity and time resolution scalar and vector wind speed, wind direction, temperature, relative humidity, barometric pressure, and solar radiation. The Fresno Supersite is coordinated with health and toxicological studies that will use these data in establishing relationships with asthma, other respiratory disease, and cardiovascular changes in human and animal subjects.

Adapting residency training. Training adaptable residents.

Graduate medical education has been criticized for failing to adequately prepare young physicians to enter the workforce upon completion of their training. In addressing this criticism, the author makes arguments both for and against this assertion. Broad qualitative changes (graduate medical education training position allocation, subspecialists' role in health care delivery, educational quality, faculty development, and faculty promotion) that graduate medical education has undergone and is undergoing are discussed. Population health management, clinical resource management, teamwork, continuous quality improvement, ethics, and evidence-based medicine are addressed as important curricular elements for residency training. Innovations in graduate medical education that are being introduced as well as those that should be tried are discussed. Finally, the author asserts that although residency education should not be vocationally driven by the needs of managed care organizations, a powerful opportunity exists for collaborative educational research between academic medicine and managed care organizations. In a health care environment undergoing rapid changes, the primary goals of graduate medical education have not significantly changed: to produce compassionate physicians with a passion for lifelong learning who have leadership skills, are critical thinkers, skilled at self-assessment, and able to adapt to the needs of the health care marketplace.

Protecting time for teaching in the ambulatory care setting.

The current drive for efficient clinical teaching threatens the educational mission of academic medical centers. With pressures to increase clinical productivity, protected time and compensation for teaching have become scarce resources for clinical teachers in all settings. Although it may yield new approaches to education, the push for efficiency may ultimately result in insufficient time for teaching and may cause some clinical preceptors to stop teaching completely. Further, it may lead to the illusion that comprehensive teaching truly requires little time. Since the future of American health care depends upon the provision of high-quality clinical education to young physicians, this situation presents a potential national crisis. In this article, the authors discuss the complex nature of teaching, its time requirements, and the special challenges of teaching in outpatient settings. To avoid overemphasizing efficiency to the detriment of education they recommend adhering to two principles: (1) academic medical centers are educational as well as training institutions, and therefore should provide a broad-based education as well as training in clinical skills; and (2) the clinical teaching process is complex and adequate time must be provided for its many phases, including planning, instructing, and reflecting. Finally, the authors make recommendations for ensuring the delivery of high-quality education in ambulatory care settings.

Defining and evaluating quality for ambulatory care educational programs.

As the training of medical students and residents increasingly moves to ambulatory care settings, clerkship and program directors must find a way to use their limited resources to guide the development and evaluation of the quality of these ambulatory-based learning experiences. To evaluate quality, directors must first define, in operational and measurable terms, what is meant by the term "quality" as it is applied to ambulatory-based education. Using educational theories and the definition of quality used by health care systems, the authors propose an operational definition of quality for guiding the planning, implementation, and evaluation of ambulatory care educational programs. They assert that quality is achieved through the interaction of an optimal learning environment, defined educational goals and positive outcomes, participant satisfaction, and cost-effectiveness. By describing the components of quality along with examples of measurable indicators, the authors provide a foundation for the evaluation and improvement of instructional innovations in ambulatory care education for the benefit of teachers, learners, and patients.

Ambulatory teaching "lite": less clinic time, more educationally fulfilling.

Typically, the primary instructional method for ambulatory care education is direct interaction between a preceptor and a learner during a patient encounter. This paper describes instructional strategies teachers and learners can use in ambulatory care training that can occur before or after scheduled clinic hours, thus providing instruction without disrupting a preceptor's busy clinic. First, they describe how preceptors and clerkship or residency-program directors can orient learners prior to their arrival at assigned sites, so that learners are better prepared to assume their patient-care responsibilities. Then they discuss strategies for making use of various types of conferences and independent learning activities to enhance learners' clinical experiences. Conferences and independent study projects that occur before clinic hours can help learners bring a higher level of thinking and clinical sophistication to their role in the ambulatory care site; conferences and independent study activities that occur after clinic hours give learners an opportunity to reinforce and expand on what they have learned during clinic. In this way, learners' educational experiences are enhanced, the best use is made of preceptors' time and expertise, and clinic efficiency is not disrupted.

Learning in the social context of ambulatory care clinics.

Social learning theory describes the process by which medical students and residents become members of the professional community of physicians. According to this theory, learning is enhanced when students and residents can share with each other their partial understandings and when they can observe and emulate the thinking and actions of expert role models. The authors make several recommendations for how social learning theory may be applied to education in ambulatory care settings: (1) preceptors should pay careful attention to orienting learners and creating legitimate roles for learners appropriate to their levels of training and ability and their educational needs; (2) since students and residents learn by observing and interacting with preceptors, competent role models should be provided; (3) to be most effective, learners should be told in advance what will be modeled, observe the demonstration, discuss what occurred and why it did or did not work effectively, and, finally, be given the opportunity to practice new actions, first with guidance and later independently; (4) when debriefing about modeled interactions, preceptors should encourage self-monitoring and self-assessment; (5) preceptors should create opportunities for collaborative learning, because collaboration with peers allows learners to discover their own misconceptions and help others to develop a richer understanding of medical practice. Implementing these guidelines in ambulatory care training will enable learners and preceptors to arrive at the shared meanings and common understandings that form the foundation of the professional medical community.

Role models' perceptions of themselves and their influence on students' specialty choices.

PURPOSE: To examine the perceptions of faculty role models to learn whether their perceptions of role models' behaviors are congruent with those of their students. METHOD: In 1996 a survey was mailed to 210 student-identified faculty role models at the University of Washington School of Medicine and the University of North Carolina at Chapel Hill School of Medicine. The nominees were asked to rate to what extent each of 32 student-identified role model characteristics was representative of their behavior. They were then asked to rank order the characteristics they felt were most important to model for students. The role models were also asked to rate how much influence they perceived themselves to have on their students' specialty choices. A final, open-ended question inquired about the single characteristics they modeled to students that most influenced the students' specialty choices. The role models' specialties were grouped as either primary care (PC) or non-primary care (NPC). Data were analyzed with several statistical methods. RESULTS: Of the 210 mailed surveys, a total of 177 were returned, for a response rate of 84%. The role models perceived their behaviors much like their students did; the role models' self-ratings were generally high for all of the student-defined characteristics. Although clinical reasoning was considered the most important characteristic to model for students, the role models also believed that enthusiasm and love for their work were the characteristics that most influenced their students' specialty choices. Few differences were found between the PC and the NPC role models. CONCLUSION: The role models in this study agreed with their students about what is important to model. They did not intentionally try to recruit students to join their specialties but felt that demonstrating enthusiasm and a sincere love for what they did has a strong influence toward this end.

Fulminant herpes hepatitis mimicking hepatic abscesses.

Fulminant hepatitis due to herpes simplex virus (HSV) in adults is a rare and deadly disease. We describe a 23-year-old woman with a 20-year history of Crohn's disease (CD) who was hospitalized with an acute febrile illness and diarrhea. A computed tomography (CT) scan of the abdomen demonstrated an intramural sigmoid colon abscess and multiple abscesses in the liver. Despite high-dose parenteral corticosteroids and broad-spectrum antibiotics, the patient remained acutely ill, with high fever and markedly elevated serum transaminase levels, but no jaundice. Sigmoid resection and wedge liver biopsy were performed at laparotomy. Histologic examination documented HSV-type intranuclear inclusions and inflammation with necrosis in both the sigmoid colon and liver specimens. The patient subsequently died despite parenteral acyclovir treatment. Although rare, fulminant hepatitis due to HSV simplex virus should be considered in the differential diagnosis of all patients with severe hepatitis. Of special note, the necrotizing liver lesions may be mistaken for pyogenic abscesses on CT scan.

Comparison of PM10 concentrations in high- and medium-volume samplers in a desert environment.

The USEPA replaced TSP with PM10 as the National Ambient Air Quality Standard for particulate matter. The commercially available PM10 sampler is a high-volume model using quartz fiber filters. In certain investigations, such as source apportionment studies, chemical analysis of the filter is necessary, however, many analyses cannot be run on quartz filters. An alternate filter such as Teflon is amenable to XRF and ion chemical analyses but is not amenable to analysis for carbon. To overcome these problems DRI constructed a medium-volume PM10 sampler that is capable of collecting particulates on both Teflon and quartz fiber filters simultaneously. This paper describes the design of the DRI medium-volume PM10 sampler, discusses a method for determining equivalence of two samplers, the results of applying the method to test the equivalence of the medium-volume sampler and a commerical high-volume sampler, and examines differences between PM10 and TSP measurements in a southwestern desert.

Pharmacokinetic and tissue residue characteristics of fenprostalene, a prostaglandin F2 alpha analog, in swine.

Fenprostalene, a prostaglandin F2 alpha analog, can be used to induce parturition in swine. As part of the approval process for that indication, pharmacokinetic characteristics of the absorption and elimination of fenprostalene and the depletion of drug residues from the principal edible tissues of swine were studied. Blood samples, urine, and feces were collected from 8 gilts (body weight, 95 +/- 1.7 kg) for up to 72 hours after a single dose of 0.5 mg of 13,14-[3H]-fenprostalene in polyethylene glycol-400 was administered SC. At intervals of 24, 48, 72, and 168 hours after dosing, 2 gilts each were killed, and samples of liver, kidney, muscle, and abdominal fat were obtained for analysis. The mean (+/- SEM) maximal concentration of fenprostalene radioequivalents in plasma (0.41 +/- 0.05 nanogram-equivalents/ml; n = 8) was observed at 12 hours and decreased biexponentially, with half-lives of approximately 8 hours and 9 days. Mean cumulative recovery (n = 4) of the administered dose by 72 hours was 61.2 +/- 5.9% in urine and 18.5 +/- 2.6% in feces. The highest tissue fenprostalene concentration was in kidneys and liver, probably reflecting the role of those organs in excreting fenprostalene. Rates of depletion of fenprostalene equivalents from the injection site, kidneys, and liver were comparable with those previously observed in cattle. The composition of residue in the liver of 2 gilts slaughtered 12 hours after SC administration of [3H]-fenprostalene was examined in a second study. Results suggested that approximately 4% of the total residue was pharmacologically potent fenprostalene or the carboxylic acid form of fenprostalene.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption and elimination of a prostaglandin F analog, fenprostalene, in lactating dairy cows.

Pharmacokinetic characteristics of the prostaglandin F2 alpha analog, fenprostalene, were studied in five lactating Holstein cows. Blood samples, milk, urine, and feces were collected for up to 7 d following a single subcutaneous injection of 1 mg of 13,14-hydrogen-3-fenprostalene in polyethylene glycol-400. The maximum concentration of tritium in plasma, observed 4 h after injection, equated to .17 ngeq/ml fenprostalene and declined with a fractional disappearance rate of .051 X h-1 to less than .04 ngeq/ml by 48 h. Likewise, milk contained .53 ngeq/ml fenprostalene at 4 h and the concentration declined with a fractional disappearance rate of .069 X h-1 to less than .03 ngeq/ml by 48 h. Milk was a very minor route of elimination of fenprostalene with only .46% of the injected dose recovered over a 7-d sampling. Recovery of tritium in urine accounted for 55% of the total dose and recovery in feces accounted for an additional 43%. Residues from fenprostalene at 7 d after injection were less than .1 ppb in all edible tissues. Differences in the molecular structure, formulation, and route of injection of fenprostalene resulted in a slower rate of absorption and elimination of this analog than previously reported for other prostaglandin products. Nonetheless, the percentage of the injected dose of fenprostalene secreted in milk was not increased appreciably, and no persistent tissue residues of fenprostalene were observed.