Modeling Water Quality in Watersheds: From Here to the Next Generation.

In this synthesis, we assess present research and anticipate future development needs in modeling water quality in watersheds. We first discuss areas of potential improvement in the representation of freshwater systems pertaining to water quality, including representation of environmental interfaces, in-stream water quality and process interactions, soil health and land management, and (peri-)urban areas. In addition, we provide insights into the contemporary challenges in the practices of watershed water quality modeling, including quality control of monitoring data, model parameterization and calibration, uncertainty management, scale mismatches, and provisioning of modeling tools. Finally, we make three recommendations to provide a path forward for improving watershed water quality modeling science, infrastructure, and practices. These include building stronger collaborations between experimentalists and modelers, bridging gaps between modelers and stakeholders, and cultivating and applying procedural knowledge to better govern and support water quality modeling processes within organizations.

A modified two temperature molecular dynamics (2T-MD) model for cascades.

Two-Temperature molecular dynamics (2T-MD) is a common approach for describing how electrons contribute to the evolution of a damage cascade by addressing their role in the redistribution of energy in the system. However, inaccuracies in 2T-MD's treatment of the high-energy particles have limited its utilisation. Here, we propose a reformulation of the traditional 2T-MD scheme to overcome this limitation by addressing the spurious double-interaction of high-energy atoms with electrons. We conduct a series of radiation damage cascades for 30, 50, and 100 keV primary knock-on atoms in increasingly large cubic W cells. In the simulations, we employ our modified 2T-MD scheme along with other treatments of electron-phonon coupling to explore their impact on the cascade evolution and the number of remnant defects. The results suggest that with the proposed modification, 2T-MD simulations account for the temperature time evolution during the ballistic phase and remove arbitrary choices, thus providing a better description of the underlying physics of the damage process.

Long-term prognosis of gastrojejunostomy in foals with gastric outflow obstruction: 16 cases (2001-2006).

REASONS FOR PERFORMING STUDY: It has been suggested that the success of gastric bypass surgery in foals for the treatment of gastric outflow obstruction is poor. However, few reports exist evaluating the long-term prognosis of these cases. OBJECTIVES: To determine the long-term success of foals, including racing records, surgically treated for gastric outflow obstruction secondary to gastroduodenal ulceration. METHODS: Medical records of foals undergoing surgical treatment of gastric outflow obstruction secondary to gastroduodenal ulceration were evaluated for clinical information. Owners, trainers and race records were evaluated regarding long-term survival and racing success. RESULTS AND CONCLUSIONS: Sixteen foals were included in the study, all treated with a gastrojejunostomy. All foals survived to immediate discharge from the hospital; 8 survived to racing age, with 7 of those entering training and 3 actually racing. Foals that did not survive to racing age had various post operative complications. The success rate for these foals appears somewhat better than that previously reported. POTENTIAL RELEVANCE: Gastrojejunostomy for the treatment of gastric outflow obstruction, secondary to gastric ulceration, is a valid treatment option for foals.

Estimating recharge rates with analytic element models and parameter estimation.

Quantifying the spatial and temporal distribution of recharge is usually a prerequisite for effective ground water flow modeling. In this study, an analytic element (AE) code (GFLOW) was used with a nonlinear parameter estimation code (UCODE) to quantify the spatial and temporal distribution of recharge using measured base flows as calibration targets. The ease and flexibility of AE model construction and evaluation make this approach well suited for recharge estimation. An AE flow model of an undeveloped watershed in northern Wisconsin was optimized to match median annual base flows at four stream gages for 1996 to 2000 to demonstrate the approach. Initial optimizations that assumed a constant distributed recharge rate provided good matches (within 5%) to most of the annual base flow estimates, but discrepancies of >12% at certain gages suggested that a single value of recharge for the entire watershed is inappropriate. Subsequent optimizations that allowed for spatially distributed recharge zones based on the distribution of vegetation types improved the fit and confirmed that vegetation can influence spatial recharge variability in this watershed. Temporally, the annual recharge values varied >2.5-fold between 1996 and 2000 during which there was an observed 1.7-fold difference in annual precipitation, underscoring the influence of nonclimatic factors on interannual recharge variability for regional flow modeling. The final recharge values compared favorably with more labor-intensive field measurements of recharge and results from studies, supporting the utility of using linked AE-parameter estimation codes for recharge estimation.

Field Test of a Hybrid Finite-Difference and Analytic Element Regional Model.

Regional finite-difference models often have cell sizes that are too large to sufficiently model well-stream interactions. Here, a steady-state hybrid model is applied whereby the upper layer or layers of a coarse MODFLOW model are replaced by the analytic element model GFLOW, which represents surface waters and wells as line and point sinks. The two models are coupled by transferring cell-by-cell leakage obtained from the original MODFLOW model to the bottom of the GFLOW model. A real-world test of the hybrid model approach is applied on a subdomain of an existing model of the Lake Michigan Basin. The original (coarse) MODFLOW model consists of six layers, the top four of which are aggregated into GFLOW as a single layer, while the bottom two layers remain part of MODFLOW in the hybrid model. The hybrid model and a refined "benchmark" MODFLOW model simulate similar baseflows. The hybrid and benchmark models also simulate similar baseflow reductions due to nearby pumping when the well is located within the layers represented by GFLOW. However, the benchmark model requires refinement of the model grid in the local area of interest, while the hybrid approach uses a gridless top layer and is thus unaffected by grid discretization errors. The hybrid approach is well suited to facilitate cost-effective retrofitting of existing coarse grid MODFLOW models commonly used for regional studies because it leverages the strengths of both finite-difference and analytic element methods for predictions in mildly heterogeneous systems that can be simulated with steady-state conditions.

The efficiency of half-mouth examinations in estimating the prevalence of periodontal disease.

Several studies, including the NIDR 1985 national survey of working adults, have used periodontal examinations of only two quadrants of the mouth to estimate the prevalence of periodontal conditions. To investigate the efficiency of half-mouth periodontal examinations, I compared the results from the examination of all teeth in a sample of 477 dentate elderly people with scores that would have been obtained if randomly selected pairs of quadrants had been examined instead. In this elderly dentate population, relatively little information would have been lost if diagonal half-mouth or same-side half-mouth scores instead of whole-mouth scores had been used to estimate the number or proportion of teeth with periodontal conditions. However, the proportion of people with the less prevalent conditions, i.e., deep pocketing and mobility, was underestimated slightly. Slightly less efficiency was also noted for the less prevalent conditions. These findings suggest that half-mouth recording may be useful for prevalence surveys, but cannot be recommended for incidence surveys or clinical trials, where incremental changes may be small.

Percent agreement, Pearson's correlation, and kappa as measures of inter-examiner reliability.

Percent agreement and Pearson's correlation coefficient are frequently used to represent inter-examiner reliability, but these measures can be misleading. The use of percent agreement to measure inter-examiner agreement should be discouraged, because it does not take into account the agreement due solely to chance. Caution must be used in the interpretation of Pearson's correlation, because it is unaffected by the presence of any systematic biases. Analyses of data from a reliability study show that even though percent agreement and kappa were consistently high among three examiners, the reliability measured by Pearson's correlation was inconsistent. This study shows that correlation and kappa can be used together to uncover non-random examiner error.

Effect of examining half the teeth in a partial periodontal recording of older adults.

Limited evidence to date has suggested that half-mouth examinations can be used in epidemiological surveys for accurate estimation of the prevalence of periodontal conditions. This study investigated the accuracy and efficiency of half-mouth periodontal examinations of mesial and buccal sites by comparing whole-mouth findings from those sites with findings that would have been obtained by examining only two randomly selected quadrants of teeth in three older dentate adult populations: 263 whites in Iowa, 309 whites in North Carolina, and 384 blacks in North Carolina. Mean half-mouth scores for gingival recession, pocket depth, attachment loss, and Extent and Severity Index were almost identical to those of mean whole-mouth scores, with correlations between means exceeding 0.93. However, the proportions of the population having selected levels of moderate or severe periodontal disease in mesial and buccal sites were underestimated by as much as 13%. This study showed that half-mouth examinations can be accurate and efficient in estimating mean periodontal measures, but may underestimate the prevalence of periodontal conditions.

Three-year tooth loss among black and white older adults in North Carolina.

The distribution and determinants of tooth loss in older adults are poorly defined, especially in Blacks, who have been underrepresented in previous studies. This study investigated, epidemiologically, the distribution and predictors of tooth loss in elder Blacks and Whites by following a random sample of older adults in North Carolina for three years. It was hypothesized that Blacks would be at greater risk of tooth loss and would have different risk factors for tooth loss. Data from 263 Blacks and 228 Whites were collected by dental examinations and interviews conducted in the participants' homes. During the three-year follow-up, 53% of Blacks and 29% of Whites lost at least one tooth. Blacks lost 13% of their remaining teeth compared with 4% for Whites. Logistic regression models showed that factors related to tooth loss for Blacks were: more S. mutans in stimulated saliva, deeper periodontal pockets, more P. intermedia in subgingival plaque, high blood pressure, limited help from others, and few symptoms of depression. For Whites, significant factors were: more lactobacilli in stimulated saliva, history of current oral pain at baseline, more alcohol consumption, no history of past use of calcium or xerostomic medications, higher income, lower occupational prestige, and increased numbers of negative life events. This study showed that older Blacks were at greater risk of tooth loss than older Whites. For both races, factors such as oral bacteria, periodontal conditions, oral symptoms, and psychosocial and economic factors are related to increased risk of tooth loss.

Variations in the social impact of oral conditions among older adults in South Australia, Ontario, and North Carolina.

Previous studies among older adults have demonstrated that oral disease frequently leads to dysfunction, discomfort, and disability. This study aimed to assess variations in the social impact of oral conditions among six strata of people aged 65 years and older: residents of metropolitan Adelaide and rural Mt Gambier, South Australia; residents of metropolitan Toronto-North York and non-metropolitan Simcoe-Sudbury counties, Ontario, Canada; and blacks and whites in the Piedmont region of North Carolina (NC), United States. Subjects were participants in three oral epidemiological studies of random samples of the elderly populations in the six strata. Some 1,642 participants completed a 49-item Oral Health Impact Profile (OHIP) questionnaire which asked about impacts caused by problems with the teeth, mouth, or dentures during the previous 12 months. The percentage of dentate people reporting impacts fairly often or very often was greatest among NC blacks for 41 of the OHIP items. Two summary variables of social impact were used as dependent variables in bivariate and multivariate least-squares regression analyses. Among dentate people, mean levels of social impact were greatest for NC blacks and lowest for NC whites, while people from South Australia and Ontario had intermediate levels of social impact (P < 0.01). Missing teeth, retained root fragments, root-surface decay, periodontal pockets, and problem-motivated dental visits were associated with higher levels of social impact (P < 0.05), although there persisted a two-fold difference in social impact across the six strata after adjustment for those factors Among edentulous people, there was no statistically significant variation in social impact among strata. The findings suggest that there are social and cultural factors influencing oral health and its social impact, and that those factors differ most between dentate blacks and whites in NC.

Physicochemical properties, pharmacokinetics, and biodistribution of gadoteridol injection in rats and dogs.

RATIONALE AND OBJECTIVES: The physicochemical properties of gadoteridol, a macrocyclic nonionic gadolinium complex, were studied together with its pharmacokinetics and biodistribution in rats and dogs. METHODS: Studies in rats were conducted after single intravenous injections at 0.1 or 0.35 mmol/kg using 153Gd-labeled gadoteridol or with seven daily doses of 0.1 mmol/kg to examine the levels of residual gadolinium in organs. Nonradioactive biodistribution and excretion studies were performed in dogs following injection at 0.1 mmol/kg. RESULTS: After injection, the dose was rapidly cleared from rat blood and excreted such that more than 90% of the dose appeared in the urine within 4 hr of injection. At 7 and 14 days postinjection, only extremely low levels of gadolinium were observed in liver and bone; these levels were two to eight times lower than the levels reported after the injection of gadopentetate dimeglumine. CONCLUSION: The extracellular distribution and rapid urinary excretion of gadoteridol is in agreement with data obtained with other gadolinium-containing chelates used as intravascular magnetic resonance imaging contrast agents. Differences observed in the long-term retention of gadolinium between gadoteridol and gadopentetate dimeglumine were consistent with the reported greater in vivo resistance to transmetallation of gadolinium macrocycles compared with the linear gadolinium chelate molecules.

The distribution and interrelationship of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, and BANA scores among older adults.

In a random sample of subgingival dental plaque samples from 375 blacks and 300 whites aged 65 and older, immunofluorescence assays for 3 target pathogens including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia, and BANA enzyme analysis were carried out. Blacks had significantly greater proportions of P. gingivalis and P. intermedia in their subgingival plaque and had significantly higher BANA scores. These assay results were investigated for concordance with each other and with 2 cariogenic salivary bacteria, Streptococcus mutans and lactobacilli. In general for both races, the periodontal pathogens were more likely to occur in combination with each other than with either S. mutans or lactobacilli. P. gingivalis and P. intermedia were more frequently associated with each other than with A. actinomycetemcomitans. There was a significant negative concordance between BANA and A. actinomycetemcomitans in whites and a significant positive concordance between BANA and P. intermedia in blacks.

Salivary flow and risk of tooth loss in an elderly population.

To investigate the relationship between salivary flow and tooth loss, 818 randomly selected dentate people aged 65 and older and living in North Carolina were administered a dental health interview and examination. A single paraffin-stimulated whole saliva sample of 3 ml was collected and flow rate was calculated. Three years later, 490 people were re-examined and tooth loss was determined. Thirty-five percent of the participants had salivary flow rates of 1.0 ml/min or less at baseline and 41% lost at least one tooth over the 3-yr follow-up. A logistic regression model controlling for marital status, race, and socioeconomic status showed that those with low salivary flow were more likely to lose at least one tooth during the 3-yr study period than were those with normal flow (odds ratio = 1.52, 95% CI = 1.02-2.24). Results from this representative study of community-dwelling older adults support the concept that compromised salivary flow is related to tooth loss. This finding should be considered in the management and prevention of oral diseases.

Five-year incidence of tooth loss in Iowans aged 65 and older.

The prevalence of missing teeth has been described for US adults, but little is known about the incidence of tooth loss in any segment of the population. This study investigated the 5-yr incidence of tooth loss in a random sample of Iowans aged 65 yr and older residing in two rural counties. These people had an average of 20 teeth at baseline and approximately 40% lost at least one tooth in the subsequent 5 yr. The incidence of tooth loss was highest for mandibular molars and lowest for mandibular canines. Men were more likely than women to lose teeth. Although we were able to identify a number of statistically significant potential risk factors for tooth loss, the multivariate models that incorporated all these factors were not good predictors of which people were at highest risk for tooth loss.

Adjustment of the M-component of the DMFS index for prevalence studies of older adults.

Cross-sectional studies of caries in older adults report a substantial number of missing teeth, making it difficult to estimate caries experience accurately. The goal of this study was to improve the method of estimating caries experience as expressed by the DMFS index in population groups with missing teeth. The adjustment was demonstrated with reference to the Piedmont 65+ Dental Study conducted on a random sample of 363 community-dwelling older adults in North Carolina who were followed for 5 years. These older dentate adults had a mean (+/-SE) of 11.7 +/- 0.5 teeth missing at baseline, 56.1 +/- 2.5 missing surfaces and a DMFS of 86.7 +/- 2.0. A predicted caries prevalence was determined from the DFS at 5 yrs plus the 5-yr DFS incidence and the baseline DFS of teeth lost during the study period. Then a formula was developed that would estimate the predicted caries prevalence as a function of the observed 5-yr DMFS. This formula provided a good estimation of caries prevalence at 5 yrs (DMFSadj) when compared with the predicted prevalence (paired t-test, p > 0.05), while prevalence was underestimated by the DFS and greatly overestimated by the traditional DMFS index. Subgroup analyses by race, sex, and periodontal status also indicated that the DMFSadj resulted in patterns of estimates similar to the predicted prevalence, while the DFS and the DMFS were likely to result in different findings. The DMFS from the time of tooth eruption also was adjusted using this formula. The resulting analyses of subgroup differences in caries were not different from the previous estimates based on the 5-yr historical data, indicating that the adjustment of all M surfaces avoids the biases inherent in the traditional DMFS and DFS indices. This study showed that predicted caries prevalence could be estimated by adjusting the M component of the DMFS. It appears that this adjustment formula can be used without obvious bias, but additional studies are needed to provide adjustment figures for populations with different caries prevalences.

A retrospective evaluation of laminitis in horses.

Case records of 202 horses treated for laminitis were reviewed with the intent of determining the long-term outcome and correlating this with digital radiographic findings and with the degree of pain associated with the laminitis. At long-term follow-up 57 horses had returned to athletic soundness (Group 1), 20 horses were intermittently lame (Group 2), 19 horses had permanent severe lameness (Group 3), 97 were dead (Group 4), and 9 were lost to follow up. Using simple regression analysis, functional outcome did not correlate with the degree of rotation (R2 = 0.004) or the presence of distal displacement (R2 = 0.139). Functional outcome did correlate with the clinical grade of laminitis (R2 = 0.504). Horses in Group 1 had significantly less distal phalangeal rotation (5.89 +/- 6.48 degrees) than did horses in Group 2 (11.10 +/- 8.19) and Group 3 (14.50 +/- 10.80), but were not significantly different from Group 4 horses (7.49 +/- 6.57). Of 96 surviving horses, 23 had evidence of distal displacement compared with 54 of 97 non-survivors. Based on these results, horses that develop distal displacement of the distal phalanx are more likely to die than are horses without distal displacement; however, the presence or absence of distal phalangeal displacement and the degree of distal phalangeal rotation cannot be used to predict the outcome of a horse with laminitis. Clinical assessment is a more reliable means of determining the final outcome and should be given precedence over radiographic findings.

Surgical repair of rib fractures in 14 neonatal foals: case selection, surgical technique and results.

REASONS FOR PERFORMING STUDY: Fractured ribs are encountered quite frequently in newborn Thoroughbred foals, often with fatal outcome. Surgical repair of fractures therefore requires consideration as a means of reducing mortality. OBJECTIVES: To evaluate the repair of rib fractures using internal fixation techniques in foals at 2 different equine hospitals following similar diagnostics and case selection. METHODS: The records of 14 foals that underwent internal fixation of fracture ribs were reviewed. Subject details, clinical presentation, diagnosis, surgical technique, post operative care and complications were recorded. Follow-up information was obtained in 7 foals. RESULTS: The fractured ribs were reduced and stabilised using reconstruction plate(s), self-tapping cortical screws and cerclage wire in 12 cases, Steinmann pins and cerclage wires in 1 case and both techniques in 1 case. Not every rib was reduced on each case. Surgical reduction was performed on an average of 2 ribs, range 1-3 ribs in each foal. At the time of writing, 4 foals had been sold, one age 2 years was in training and 2 others died from unrelated causes. CONCLUSIONS: Our data support the use of surgical stabilisation utilising reconstruction plates, self-tapping cortical screws and cerclage wire for selected cases of thoracic trauma in neonatal foals. The use of Steinmann pins may be suboptimal due to cyclic failure, implant migration and the potential for iatrogenic internal thoracic trauma. POTENTIAL RELEVANCE: Foals with existing extensive internal thoracic trauma resulting from rib fracture(s), or the potential for such trauma, previously considered to have a guarded to poor prognosis for survival, may be successfully managed with internal fixation of selected fracture sites.

Validation of oral status indicators.

In planning programmes and developing policy, dental public health officials rely on epidemiological data in the form of composite measures such as the DMFT index. However, the DMFT is often not sufficiently sensitive to detect differences in oral health between population groups. Measures that selectively weight components of the DMFT may be better dental indicators. Sheiham, Maizels and Maizels (1987) suggested a functional measure (FM) that weights filled and sound teeth equally and a tissue health (T-health) measure that differentially weights decayed, filled, and sound teeth. For the present analysis, these indicators were divided by 28 to make their range 0 to 1. The modified indexes are called FMI and THI. Carpay et al. (1988) also suggested a dental health index (DHI) that scores a subset of teeth. Data from 797 participants in the 1980 Iowa Survey of Oral Health that included eight independent variables were used to perform stepwise regression on DMFT, FMI, THI, and DHI to assess how well the independent variables correlated with these four dental indicators. R-square values were 0.37 for FMI and 0.36 for THI, but only 0.19 for DHI and 0.12 for DMFT, suggesting that the FMI and THI were more sensitive as dental health indicators. In addition, calculations made on aggregate data published from three national surveys show that the FMI and THI can detect changes in oral health over time. Because the FMI and THI are as easy to measure and calculate as the DMFT, but appear to be more sensitive, they show promise as indicators of oral health status.

Is it time to reassess the public health implications of periodontal diseases? A review of current concepts.

In 1981 the American Association of Public Health Dentists' Subcommittee on Preventive Periodontics called for a national initiative toward controlling periodontal disease, including the development of national policy statements from national dental organizations and the development of education programs for the public and the profession. Since the 1981 report, the findings of a diverse group of studies raises a variety of questions about the prevalence of periodontal diseases, the etiology and progression of the diseases, and the feasibility and practicality of controlling them. An examination of this new information leads to the conclusion that it is time to reassess the public health implications of periodontal diseases.

Methodological considerations in a dental epidemiologic survey of an elderly population.

The proportion of the US population that is age 65 or over is increasing and edentulism rates are declining. The community's elderly population is becoming an increasingly important constituency for dental public health. Little is known, however, about the actual oral health status of these people. An assessment of oral health in the elderly presents many considerations not found in an assessment of oral health among children. The selection of subjects to represent all the elderly in the community is difficult. Caries assessment is complicated by the need to distinguish between coronal caries and root caries and by the inability to determine accurately the reason for prior tooth loss. Periodontal assessment is more difficult than in younger populations because the conditions tend to be advanced. The recruitment of participants is difficult because each potential subject must be contacted individually. These assessments are needed so the oral status of adult populations can be determined.