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PubMed2005

Logistic trajectory maps and aerosol mixing due to asynchronous flow at airway bifurcations.

Aerosols too large for significant Brownian transport, and too small for significant inertial transport, are nonetheless known to deposit deep in the lung, and are associated with increased risk of pulmonary disease. Classical models fail to explain such transport. We hypothesized that kinematic irreversibility in ventilation, arising from velocity saddle-points or from flow asynchrony at airway bifurcations, may be the fundamental transport mechanism. Our experimental evidence shows striking trajectory irreversibility in rat lungs ventilated with 2-color polymerizable silicones, representing resident and tidal gas. The striated patterns in small airways, even after one ventilatory cycle, support our hypothesis. Here we analyze bifurcating flow asynchrony in a simplified one-dimensional model. We find: unexpected richness and chaos in particle trajectories; almost all trajectories visit all spatial positions; surprisingly, there is complete mixing-the limiting concentration is spatially uniform. This is a new finding supporting the idea that kinematic irreversibility is a potent mixing and transport mechanism for aerosols deep in the lung.

Aerosols↗
PubMed1997

Logistic analysis of shovel and Carabelli's tooth traits in a Caucasoid population.

Caucasoid populations differ from Mongoloids by having a high prevalence of Carabelli's trait and a low prevalence of shovel trait. This study was conducted to investigate the association between the shovel and the Carabelli's traits in a Caucasoid population. The research design sought a Caucasoid population at Milwaukee of Wisconsin in United States. The Caucasoid group selected for study was the European descendant. The effects of sex and age on Carabelli's trait were controlled in this investigation, as was the association between tooth size and Carabelli's trait. Results show that males were more likely to have Carabelli's trait expressed on teeth than females. The buccolingual diameter of Carabelli's trait teeth was larger than that of teeth without the trait. After adjusting for sex, age, and tooth size, the existence of the shovel trait decreased the likelihood of having Carabelli's trait which shows an significant effect.

Asian People↗
PubMed2000

Iron stores and coronary artery disease: a clinical application of a method to incorporate measurement error of the exposure in a logistic regression model.

Rates of coronary artery disease (CAD) increase sharply after menopause. We examined the hypotheses that high iron stores, as measured by plasma ferritin levels, are a risk factor for CAD and that the increase in iron stores after menopause is at least in part responsible for the rise in CAD in women. We also investigated measurement error of plasma ferritin using a Bayesian conditional independence model and incorporated it into the estimation of the odds ratio (OR) for males. Cases had >/=1 coronary artery stenosis >/=70%. Controls had no visible coronary lesions on angiography. The median plasma ferritin level was 48 mg/L (interquartile range: 28 to 86) among 244 cases and 45 mg/l (24 to 85) among 140 controls. The multivariate analyses among females, males, and females and males combined did not support an association between plasma ferritin levels and CAD (OR for one unit change in log ferritin 1.01, 95% CI 0.71-1.44, OR 0.95, 95% CI 0.66-1.37 and OR 0.95, 95% CI 0.75-1.21, respectively). Accounting for the measurement error of ferritin in males slightly improved the precision of the estimate of the OR but did not unmask an association (OR: 0.94, 95% CI 0.69-1.30). We conclude that high ferritin levels before or after menopause are not associated with CAD. Measurement error might be considered in situations where a one-time measurement is assumed to be representative of long-term exposure.

Aged↗
PubMed2000

Distribution of pharmaceuticals--a Norwegian logistic perspective.

There is a general concern about rising costs of pharmaceutical expenses. One political measure is a more efficient distribution system, which can take the form of new channels for retailing. In Norway mail-order pharmacy (MOP) has been brought to the agenda due to the recently proposed law regulating pharmacies ("Apoteklov"), market developments abroad, demand for self-medication, the increase in OTC-products and advances in information technology. Mail-order pharmacy involves direct delivery of medications through postal mail to patients or those responsible for dispensing medication. With reference to the USA, mail-order pharmacy has filled a niche in the market and several other countries are following. We are convinced that it is possible to maintain a high level of service quality in the sense of safety, counselling and compliance, and that there is a potential to develop a model for this distribution form in Norway. We believe that the actors in the Norwegian pharmaceutical market are better served in taking a more active role in this area and where possible initiating pilot projects in mail-order distribution. The pharmacists will continue to play an important role as a retail outlet and should, with their influence over patients, their knowledge and experience, contribute towards developing MOP to be a safe and complementary sales outlet. Developing such a solution demands the right balance between performance and quality on the one hand and efficiency on the other; two criteria, which we believe, do not contradict each other.

Humans↗
PubMed2003

Pressure ulcer risk assessment: application of logistic analysis.

AIM: The aim of this study was to investigate the relative importance of key factors affecting the likelihood of hospital acquired pressure ulcers, thus offering the groundwork for the development of an empirically-based risk assessment scale. It also evaluated the predictive performance of the underlying empirical model and compared its classification ability with the empirically observed ability of the Waterlow risk assessment scale. BACKGROUND: Pressure ulcers impose a significant burden on patients and carers and demand substantial resources from the health care system. There is, however, a lack of systematic empirical research on which to base the development of risk assessment measurement tools. METHODS: Multivariate statistical methods were applied to data derived from the records of a cross-sectional sample of around 500 randomly selected inpatient episodes drawn from the population of admissions to a single unit in a large acute hospital during a 2-year period (October 1996 to September 1998). Double-checking of a randomly selected 25% sample of the original records and careful screening out of records with incomplete information or inconsistent values was carried out to ensure a high quality sample. Logit analysis was used to investigate the relative contribution of risk factors, such as continence, skin condition, mobility and inter-hospital transfer to the risk of hospital-acquired pressure ulcer occurrence, whilst cross-validation techniques were employed to check the predictive performance of the model. RESULTS: The results suggest that a simplified version of the Waterlow risk assessment tool has satisfactory predictive ability and the potential for further development. CONCLUSIONS: Two main conclusions emerged from this study. First, it is both feasible and worthwhile to pursue improvement in the development of risk assessment tools using statistical methods. Second, locally-determined risk factors will need to be incorporated into the construction of future risk assessment scales.

Aged↗
PubMed2003

Predictors of psychiatric disorders in liver transplantation candidates: logistic regression models.

This study has two goals. The first goal is to assess the prevalence of psychiatric disorders in orthotopic liver transplantation (OLT) candidates by means of standardized procedures because there has been little research concerning psychiatric problems of potential OLT candidates using standardized instruments. The second goal focuses on identifying predictors of these psychiatric disorders. One hundred sixty-five elective OLT candidates were assessed by our unit. Psychiatric diagnoses were based on the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Patients also were assessed using the Hamilton Depression Rating Scale (HDRS) and the Spielberger Anxiety Index, State and Trait forms (STAI-X1 and STAI-X2). Severity of cirrhosis was assessed by applying Child-Pugh score criteria. Chi-squared and general linear model analysis of variance were used to test the univariate association between patient characteristics and both clinical psychiatric diagnoses and severity of psychiatric diseases. Variables with P less than.10 in univariate analyses were included in multiple regression models. Forty-three percent of patients presented at least one psychiatric diagnosis. Child-Pugh score and previous psychiatric diagnoses were independent significant predictors of depressive disorders. Severity of psychiatric symptoms measured by psychometric scales (HDRS, STAI-X1, and STAI-X2) was associated with Child-Pugh score in the multiple regression model. Our data suggest a high rate of psychiatric disorders, particularly adjustment disorders, in our sample of OLT candidates. Severity of liver disease emerges as the most important variable in predicting severity of psychiatric disorders in these patients.

Adult↗
PubMed2002

Logistic regression.

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Data Interpretation, Statistical↗
PubMed1998

A logistic regression model for analyzing the relation between dentists' attitudes, behavior, and knowledge in oral radiology.

The aim was to study the relation between risk attitude and knowledge in technical, patient-oriented, and organizationally related behavior within oral radiology. A questionnaire was mailed to 2000 randomly selected dentists listed in the register of the Swedish Dental Society, with a response rate of 69.3%. Regression analysis was used for analyzing the effects of the independent variables knowledge, risk attitude, continuing education in oral radiology, counties with specialists in oral radiology, type of practice, work experience, and sex on three categories of dependent variables: 1) technical behaviors: type of film, type of collimator, dose level, frequency of change of chemicals; 2) patient-oriented behaviors: use of patient protection barriers, strict indications for performing full-mouth X-ray examinations and bitewing radiography on new patients and recall patients; and 3) organizationally related behaviors: delegation of X-ray examinations to dental auxiliaries, influence on choice of collimator, influence on choice of film. Knowledge and education had strong direct effects for most of the dependent variables. The technical behaviors were mainly influenced by knowledge, education, and risk attitude, while organizationally related behaviors were influenced by type of practice and sex. The patient-oriented behaviors were influenced by a number of independent variables, such as education, type of practice, work experience, and sex. The present results indicate that both knowledge and the organizational context of dentists influence work.

Adult↗