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PubMed2006

Prey risk allocation in a grazing ecosystem.

Understanding the behaviorally mediated indirect effects of predators in ecosystems requires knowledge of predator-prey behavioral interactions. In predator-ungulate-plant systems, empirical research quantifying how predators affect ungulate group sizes and distribution, in the context of other influential variables, is particularly needed. The risk allocation hypothesis proposes that prey behavioral responses to predation risk depend on background frequencies of exposure to risk, and it can be used to make predictions about predator-ungulate-plant interactions. We determined non-predation variables that affect elk (Cervus elaphus) group sizes and distribution on a winter range in the Greater Yellowstone Ecosystem (GYE) using logistic and log-linear regression on surveys of 513 1-km2 areas conducted over two years. Employing model selection techniques, we evaluated risk allocation and other a priori hypotheses of elk group size and distributional responses to wolf (Canis lupus) predation risk while accounting for influential non-wolf-predation variables. We found little evidence that wolves affect elk group sizes, which were strongly influenced by habitat type and hunting by humans. Following predictions from the risk allocation hypothesis, wolves likely created a more dynamic elk distribution in areas that they frequently hunted, as elk tended to move following wolf encounters in those areas. This response should dilute elk foraging pressure on plant communities in areas where they are frequently hunted by wolves. We predict that this should decrease the spatial heterogeneity of elk impacts on grasslands in areas that wolves frequently hunt. We also predict that this should decrease browsing pressure on heavily browsed woody plant stands in certain areas, which is supported by recent research in the GYE.

Animals↗

PubMed2003

Issues of replicability in Monte Carlo modeling: a case study with a pesticide leaching model.

Sensitivity and uncertainty analyses based on Monte Carlo sampling were undertaken for various numbers of runs of the pesticide leaching model (PELMO). Analyses were repeated 10 times with different seed numbers. The ranking of PELMO input parameters according to their influence on predictions for leaching was stable for the most influential parameters. For less influential parameters, the sensitivity ranking was severely influenced by the seed number used. For uncertainty analyses, probabilities of exceeding a particular concentration were significantly influenced by the seed number used in the random sampling of values for the two parameters considered, even for those cases in which 5,000 model runs were undertaken (coefficient of variation of 10 replicated analyses, 5%). A decrease in the variability of exceedance probabilities could be achieved by further increasing the number of model runs. However, this may prove to be impractical when complex deterministic models with a relatively long running time are used. Attention should be paid to replicability aspects by modelers when devising their approach to assessing the uncertainty associated with the modeling and by decision makers when examining the results of probabilistic approaches.

Environmental Monitoring↗

PubMed2004

The long-term fate of polychlorinated biphenyls in San Francisco Bay (USA).

A simple one-box mass budget model is presented as a first step toward a quantitative understanding of the long-term fate of polychlorinated biphenyls (PCBs) in San Francisco Bay (USA). Sensitivity analysis indicated that the most influential input parameters were degradation half-life in sediment, Kow, outflow, average PCB concentration in sediment, and depth of the active sediment layer. Moderately influential parameters included organic carbon content of suspended solids, sediment burial mass transfer coefficient, and Henry's law constant. If external loading could be eliminated entirely, the mass of PCBs in the bay is predicted to drop to half of the present value in 20 years. The model predicts that sustained loading of 10 kg year(-1) would prevent the total PCB mass in the bay from ever dropping below 10% of the present mass. With a sustained loading of 20 kg year(-1), the model predicts that the total PCB mass would never fall below about 25% of the present mass. The half-lives in the bay for the individual PCB congeners evaluated in this report ranged from four years for PCB 18 to 30 years for PCB 194.

California↗

PubMed2005

Evaluation of pharmacological treatment of impulsivity in children with attention deficit hyperactivity disorder.

We used an assessment that involved competing reinforcer dimensions in a concurrent-schedules arrangement to examine the effects of stimulant medication on impulsivity (i.e., sensitivity of choices to reinforcer immediacy relative to rate, quality, and effort) with 4 students with attention deficit hyperactivity disorder. The assessments were administered in the context of a double-blind, placebo-controlled, counterbalanced reversal design. Reinforcer immediacy was the most influential dimension for 3 of the students and the second most influential dimension for 1 of the students across placebo and medication conditions; medication did not affect these sensitivities.

Adolescent↗

PubMed2002

The cost-effectiveness of interleukin-1 genetic testing for periodontal disease.

BACKGROUND: A genetic test for a composite interleukin-1 (IL-1) genotype is being marketed to predict risk for progression of periodontal disease. The objective of this study was to determine the clinical scenario required to produce cost-effective results with the use of IL-1 testing to identify high-risk patients. METHODS: A disease simulation model was developed using decision-analytic techniques and a 30-year time frame. RESULTS: Using different modeling scenarios, the genetic test produced results ranging from cost savings of $830,140 and 52.8 fewer cases of severe periodontitis to increased costs of $300,430 and 3.6 additional cases of severe periodontitis (per 1,000 patients). Three parameters in the analysis were highly influential: 1) the compliance rate for maintenance therapy in test positive versus non-tested patients; 2) the effectiveness of non-surgical therapy; and 3) the relative risk of disease progression for test positive patients. CONCLUSION: The model produced a wide range of outcomes reflecting our incomplete understanding of the biology, optimal treatment, and genetic susceptibility of periodontal diseases. However, the model demonstrates that three clinical parameters are highly influential in determining if IL-1 testing can be implemented in a primary care setting in a cost-effective manner.

Adult↗

PubMed2001

Smoking cessation in women. Special considerations.

Women may be at relatively greater risk of smoking-related diseases than men but tend to have less success than men in quitting smoking. The failure of most outcome studies to report results by gender and the lack of statistical power for detecting significant gender differences currently do not allow for many firm conclusions to be drawn about smoking cessation rates in women, but several trends warrant attention and further study. First, the difference in cessation rates for women versus men may be even greater in trials of nicotine replacement therapies (NRT). This suggests that women benefit less from NRT relative to men, although this difference may depend on the particular form of NRT (e.g. inhaler versus gum). On the other hand, some non-NRT medications may reverse the poorer outcome of women, producing quit rates in women comparable with those in men. Gender differences in outcome, as well as overall success rates, with NRT and some of the non-NRT medications appear to be enhanced when treatment includes substantial behavioural counselling. However, while several of the non-NRT medications may be particularly appropriate to consider for treating women trying to quit smoking, adverse effects may limit widespread use of some of these drugs, such as clonidine and naltrexone. Thus, even if the gender differences in outcome with NRT versus non-NRT drugs are confirmed in further research, such findings do not necessarily justify limiting NRT use in women, because such treatment is clearly effective and is likely to be safer and more readily available than non-NRT medications. Nevertheless, study of the mechanisms by which some non-NRT drugs are effective in women may aid our understanding of factors that are more influential in smoking behaviour in women than in men. Secondly, smoking cessation treatment for women must address several other issues that often emerge, and these are most likely to require behavioural counselling that is tailored to these problems. These issues include concern about bodyweight gain, restrictions on medication use in pregnant smokers, variability in mood and withdrawal as a function of menstrual cycle phase, harnessing social support to foster abstinence, and the possibility that smoking-associated environmental cues may be more influential in smoking behaviour in women than men. Greater attention to gender differences in clinical trial outcomes and to addressing concerns of women smokers may aid in the development of substantially improved smoking cessation interventions for women.

Female↗

PubMed2003

Hype in health reporting: "checkbook science" buys distortion of medical news.

The greatest danger to public health might be "checkbook science": research intended not to expand knowledge or to benefit humanity but to sell products. Much of the media coverage of health news stories is based on public relations efforts on behalf of the companies that sell the products, including pharmaceutical companies, diet clinics, or doctors selling new techniques. The author presents three case studies of how companies selling medical products effectively but invisibly shaped recent news coverage of medical products: fen-phen diet pills, breast implants, and hormone replacement therapy. All involve subtle strategies whereby physicians and other experts paid by corporate interests are influential because they are perceived to be objective medical experts. Articles in prestigious medical journals are sometimes ghostwritten by individuals paid by companies or are based on biased analyses or interpretations shaped by corporate interests. Nonprofit organizations that tout the benefits of specific medical products also may be part of the public relations efforts of the companies making the product. Meanwhile, important newsworthy studies are ignored by the mass media when corporate interests do not publicize or pitch the results to influential reporters and producers.

Biomedical Research↗

PubMed2006

Identifying illness parameters in fatiguing syndromes using classical projection methods.

OBJECTIVES: To examine the potential of multivariate projection methods in identifying common patterns of change in clinical and gene expression data that capture the illness state of subjects with unexplained fatigue and nonfatigued control participants. METHODS: Data for 111 female subjects was examined. A total of 59 indicators, including multidimensional fatigue inventory (MFI), medical outcome Short Form 36 (SF-36), Centers for Disease Control and Prevention (CDC) symptom inventory and cognitive response described illness. Partial least squares (PLS) was used to construct two feature spaces: one describing the symptom space from gene expression in peripheral blood mononuclear cells (PBMC) and one based on 117 clinical variables. Multiplicative scatter correction followed by quantile normalization was applied for trend removal and range adjustment of microarray data. Microarray quality was assessed using mean Pearson correlation between samples. Benjamini-Hochberg multiple testing criteria served to identify significantly expressed probes. RESULTS: A single common trend in 59 symptom constructs isolates of nonfatigued subjects from the overall group. This segregation is supported by two co-regulation patterns representing 10% of the overall microarray variation. Of the 39 principal contributors, the 17 probes annotated related to basic cellular processes involved in cell signaling, ion transport and immune system function. The single most influential gene was sestrin 1 (SESN1), supporting recent evidence of oxidative stress involvement in chronic fatigue syndrome (CFS). Dominant variables in the clinical feature space described heart rate variability (HRV) during sleep. Potassium and free thyroxine (T4) also figure prominently. CONCLUSION: Combining multiple symptom, gene or clinical variables into composite features provides better discrimination of the illness state than even the most influential variable used alone. Although the exact mechanism is unclear, results suggest a common link between oxidative stress, immune system dysfunction and potassium imbalance in CFS patients leading to impaired sympatho-vagal balance strongly reflected in abnormal HRV.

Adult↗

PubMed1977

Visual set and anxiety in the Stroop phenomenon.

The effects of a visual set, the Stroop phenomenon, and anxiety--as measured by the Spielberger State-Trait Anxiety Inventory--upon response latency were examined. Three variations of the set were presented, a color congruent with the response color, a color conflicting with the response color, or no color. Two response conditions were required, reading the color word or reporting the color in which the word was printed. "Reporting the color" had a significantly longer response latency than "reading the word" for all 60 subjects, female volunteers from freshman psychology classes. There was also a significant interaction between anxiety and the Stroop. The medium-anxiety group showed the least discrepancy between the response conditions of the Stroop, indicating the interference effect present in the Stroop phenomenon was least influential for this group. A consistent though not significant difference between the congruent set and conflicting set conditions for the color response as opposed to the word response indicated that, when the set is similar to the response, it is more influential than when it is unrelated.

Adolescent↗

PubMed1997

Magnitude estimation scaling of annoyance in response to rock music: effects of sex and listeners' preference.

The present study parallels an earlier one Fucci, Petrosino, and Banks in 1994 concerned with sex and listeners' preference effects on magnitude estimation scaling of rock music. The difference between the two studies is that the subjects in 1994 were asked to scale "loudness" while the present subjects were asked to scale "annoyance." The prior results and those of the present study were different, i.e., the women's preference appeared influential in the magnitude estimation scaling of rock music previously but here the men's preference appeared influential. If subjects are instructed to judge the annoyance of an auditory signal, they may respond differently than if asked to judge its loudness. Judgments of annoyance appear to be more context dependent whereas loudness judgments may reflect a perceptual process more closely related to physical aspects of the signal.

Analysis of Variance↗

PubMed2006

Inbreeding trends and pedigree analysis of Irish dairy and beef cattle populations.

The objective of this study was to determine the inbreeding levels and to analyze the pedigree of Irish purebred populations of Charolais, Limousin, Hereford, Angus, and Simmental beef cattle, as well as the Holstein-Friesian dairy breed. Pedigree analyses included quantifying the depth of known pedigree, average generation intervals, effective population size, the effective number of founders, ancestors, and founder genomes, as well as identifying the most influential animals within the current population of each breed. The annual rate of increase in inbreeding over the past decade was 0.13% (P < 0.001) in the Hereford, 0.06% (P < 0.001) in the Simmental, and 0.10% (P < 0.001) in the Holstein-Friesian breeds. Inbreeding in the other breeds remained relatively constant over the past decade. Herefords had the greatest mean inbreeding in 2004, at 2.19%, whereas Charolais had the lowest, at 0.54%. Over half of each purebred population in 2004 was inbred to some degree; the population with the greatest proportion of animals inbred was the Hereford breed (85%). All 6 breeds displayed a generation interval of approximately 6 yr in recent years. In the pure-bred females born in 2004, the 3 most influential animals contributed between 11% (Limousin) and 24% (Hereford) of the genes. Effective population size was estimated for the Hereford, Simmental, and Holstein-Friesian only, and was 64, 127, and 75, respectively. The effective number of founders varied from 55 (Simmental) to 357 (Charolais), whereas the effective number of ancestors varied from 35 (Simmental and Hereford) to 82 (Limousin). Thus, despite the majority of animals being inbred, the inbreeding level across breeds is low but rising at a slow rate in the Hereford, Simmental, and Holstein-Friesian.

Animals↗

PubMed1996

Dental caries determinants in an adult Portuguese population and a comparison with Norwegian adults.

The present epidemiologic dental caries study indicates a high number of decayed surfaces (mean, 13.5 +/- 11.8 (SD)) in a Portuguese population of 30- to 39-year-olds from Porto. The most influential determinants for variation in carious surfaces were oral hygiene, gender, salivary buffer capacity, and missing teeth. By entering the most influential independent variables in a final multiple classification analysis, the total explained variance in carious surfaces was 27%. A comparison with results from a similar Norwegian dental health study showed that the biologic factors of importance for number of carious surfaces were the same, whereas the sociocultural determinants differed.

Adult↗

PubMedDate not supplied

Analysis of thermal parameters obtained during phase III trials of hyperthermia as an adjunct to radiotherapy in the treatment of breast carcinoma.

An analysis of 351 HT treatment sessions administered to 101 patients receiving radiotherapy and hyperthermia (RT + HT) who were entered into Phase III concurrent randomized trials for recurrent (BrR) and intact (BrI) breast tumours is presented. A complete response (CR) was recorded in 50 of 84 (59.5%) fields in the case of recurrent breast patients and in 10 of 17 (59%) fields in the case of the intact breast patients. In comparison, 15 of 60 (25%) patients entered into BrR who received RT alone and 8 of 12 (66.7%) patients receiving RT alone entered into BrI trial achieved CR. A set of thermal parameters is defined and evaluated on a treatment by treatment basis. Patient and tumour characteristics influential on CR are identified and thermal parameters which have additional prognostic value are investigated. Multivariate logistic analysis of the non-thermal data showed that maximum depth of tumour, presence or history of disease outside the treated area and RT regimen were most influential on CR. Tumour volume (cm3) (OR = 0.996, 95% CI = 0.993-1.004, p = 0.08) was not a strong prognostic covariate; tumour area and linear dimensions were even less significant (p = 0.41). The cumulative minimum thermal isoeffect dose (equivalent minutes at 43 degrees C) accrued over the 1st, 1st and 2nd, and 1st, 2nd and 3rd treatment sessions was the only thermal parameter to exhibit an association with CR consistently, Other thermal parameters found to contribute to the predictive models were MINTIME > 42 degrees C calculated for the first treatment session and %sensors > 43 degrees C (peak) calculated for the 2nd treatment session.

Aged↗

PubMed1997

Morning versus afternoon gymnastic time and diurnal and seasonal changes in psychophysiological variables of school children.

The aims of this study were to document time-related (morning versus afternoon) effects of physical activities (gymnastics) on a set of physiological and psychological variables in school children, including diurnal changes. For the study, 61 boys and 69 girls, 6 to 11 years of age, volunteered. They were considered healthy according to routine clinical criteria. They were synchronized with diurnal activity from around 07:00 to 21:00 and nocturnal rest, time of year being taken into account. Tests were performed at school during 4 weeks of 4.5 days of school at fixed clock hours: 09:00, 11:00, 14:00, and 16:00. Gym time was randomized with regard to week order and season. Four different classes (39 boys and 38 girls) were involved in psychophysiological tests, and two different classes (22 boys and 31 girls) collected saliva samples for morning free cortisol determination. Both t-test and three-factor analysis of variance (ANOVA) were used for statistical analyses. Better performances were obtained in June than in mid-winter with reference to letter cancellation and random number addition tests. As a group phenomenon, morning (09:00 to 10:00) versus afternoon (14:00 to 15:00) gym was not an influential condition with regard to sleep duration, oral temperature, self-rated fatigue and drowsiness, letter cancellation, addition tests, or salivary cortisol. However, gym-time-related differences were observed in classes of younger subjects (e.g., 6-7 years) with regard to self-rated fatigue and the letter cancellation test. Such variability among subgroups suggests that interindividual differences are likely to exist in younger children with regard to manipulation of environmental factors. In addition, gym itself (without gym time consideration) may be an influential factor with regard to diurnal patterns of some variables (e.g., the letter cancellation test).

Body Temperature↗

PubMed1995

Nutritional and dental implications of high and low intakes of sugar.

Currently, in nutrition there are major anxieties over the bearing of high intakes of energy and certain nutrients (e.g. fat, sugar) on health/ill-health. Two questions concern sugar: does a high intake (1) cause a deleterious imbalance or dilution of macro- and micro-nutrients? and (2) does it promote degenerative diseases, in particular dental caries? As to the first question, evidence from a variety of contexts indicates that nutrient intakes are not reduced; rather they are increased. Additionally, one accompaniment of a high sugar intake is a reduced intake of fat, one of the primary aims of nutritional guidelines. However, these do not license excessive sugar consumption. As to sugar and degenerative diseases, evidence is lacking that sugar intake is significantly influential other than for dental caries. An examination of evidence indicates sugar consumption to be a weak factor in caries development; its intake explains little of the variance in caries occurrence. Clearly, additional factors are influential-genetic, exposure to fluoride, and dietary components other than sugar. Early detection of the relatively small proportion of caries-prone individuals by appropriate markers, must be sought.

Adolescent↗

PubMed1987

Depression among alcoholics.

The relationships of cognition, health status, and age to depression among alcoholics were studied. Eighty male alcoholics in an alcohol treatment unit were rated on health status and given a battery of psychological tests and scales. These included the Hooper VOT (cognition) and several self-rated depression indices: MMPI-Depression, MCMI-Dysthymic, BDI-Total (BDI-Somatic and BDI-Psychological), and the Geriatric Depression Scale (GDS). Results showed that depression was present in this sample at mild clinical levels. Regression analyses showed that age was the most influential factor on the MMPI-D and BDI-Somatic. Age also was most influential on the GDS, with health status contributing. However, except for somatic depression, the amount of explained variance was small. Despite this, it is argued that age is a contributing factor to depression among alcoholics, especially the somatic elements of depression.

Adult↗

PubMed2001

Decision analysis for small, asymptomatic intracranial arteriovenous malformations.

OBJECT: Asymptomatic intracranial arteriovenous malformations (AVMs) represent a clinically challenging problem because of the complex decision making that must be undertaken prior to beginning any type of treatment. In addition, the relative infrequency of these lesions means that there is relatively little experience reported in the literature. The authors use a decision-analysis technique to model the considerations that go into determining the treatment of these lesions in an effort to quantify the various risks and overall benefits conferred by the following three treatment strategies: observation/natural history, microsurgery, and stereotactic radiosurgery. METHODS: The authors conducted a thorough literature search to elucidate the risks and outcomes associated with each treatment option. These values were used to build and run a comprehensive Markov model to determine a base-case analysis. All of the input variables were also subjected to sensitivity analysis to identify the most influential input variables and the crossover points in which favored strategies changed. The base-case analysis suggested that microsurgery was the favored treatment option because this hypothetical cohort accumulated 21.53 quality-adjusted life years (QALYs) over the course of the model compared with the 16.97 QALYs and 16.40 QALYs for stereotctic radiosurgery and observation, respectively. Sensitivity analysis demonstrated that overall major neurological morbidity and mortality were the most influential input variables both perioperatively and during the radiosurgical "latent" period (that is, up to 2 years posttreatment). The maximum acceptable perioperative combined major neurological morbidity and mortality rate was 6.8%. The latent period combined major neurological morbidity and mortality would need to be 0.7% to make radiosurgery favorable in this analysis. CONCLUSIONS: Results of this decision analysis model suggest that microsurgery in the hands of experienced cerebrovascular surgeons, who can expect a less than 6.8% combined rate of major neurological morbidity and mortality, offers patients a greater overall quality of life over time.

Algorithms↗

PubMed1997

Relationship between nutritional intake and dental caries experience of junior high students.

This study was designed to investigate the relationship between nutritional intake and caries experience of junior high school students. The sample consisted of 295 boys and 356 girls in Kangwha county. Dependent variables were total caries experience, occlusal surface caries experience, smooth surface caries experience and DMFS score (Decayed, Missing, Filling Tooth Surface score). Independent variables such as pit and fissure retentiveness of first molars, oral hygiene status, intraoral acidogenicity were also measured by dentists. Other independent variables such as toothbrushing habits, socioeconomic conditions, between-meal eating habits, and daily nutritional intake were determined during an interview. Univariate and multivariate analysis was performed to evaluate how nutritional intake influences caries experience. The results were as follows: 1. The most influential factor on dental caries experience was pit and fissure retentiveness. 2. Dietary fiber and potassium were the significant nutritional factors on total caries experience and occlusal caries experience, and niacin was the significant nutritional factor on smooth surface caries. 3. DMFS score was positively associated with the daily amount of carbohydrate and niacin intake, and negatively associated with total energy intake. The above results suggested that pit and fissure retentiveness was the most influential factor on caries experience. However, in this study, the intake of potassium and niacin was identified to influence the caries experience in addition to confirming the well-known relationship between fiber and carbohydrate intake.

Adolescent↗