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Many Variables (many + variable)
Selected AbstractsConsiderations in measuring the electrical potentials of metallic restorations in vivoJOURNAL OF ORAL REHABILITATION, Issue 11 2000E. J. Sutow Many variables are believed to affect the accurate measuring of metallic restoration electrical potentials. This study examined the effects of intra- versus extra-oral location of the reference electrode, the type of metallic probe used to make contact with the restoration, and scratching and brushing of the restoration surface. Dental amalgam restorations were measured in 40 human subjects. Results showed that only the location of the reference electrode affected the central tendency of the potential. The study discusses the significance of some experimental variables in the accurate measuring of metallic potentials and the need to consider individual subject differences when statistically analysing for the central tendency of a sample. [source] Bayesian modelling of catch in a north-west Atlantic fisheryJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 3 2002Carmen Fernández Summary. We model daily catches of fishing boats in the Grand Bank fishing grounds. We use data on catches per species for a number of vessels collected by the European Union in the context of the Northwest Atlantic Fisheries Organization. Many variables can be thought to influence the amount caught: a number of ship characteristics (such as the size of the ship, the fishing technique used and the mesh size of the nets) are obvious candidates, but one can also consider the season or the actual location of the catch. Our database leads to 28 possible regressors (arising from six continuous variables and four categorical variables, whose 22 levels are treated separately), resulting in a set of 177 million possible linear regression models for the log-catch. Zero observations are modelled separately through a probit model. Inference is based on Bayesian model averaging, using a Markov chain Monte Carlo approach. Particular attention is paid to the prediction of catches for single and aggregated ships. [source] An evidence-based appraisal of splinting luxated, avulsed and root-fractured teethDENTAL TRAUMATOLOGY, Issue 1 2008Bill Kahler For this systematic review of splinting of teeth that have been luxated, avulsed or root-fractured, the clinical PICO question is (P) what are splinting intervention decisions for luxated, avulsed and root-fractured teeth (I) considering that the splinting intervention choice may include (i) no splinting, (ii) rigid or functional splinting for the different types of trauma and (iii) different durations of the splinting period (C) when comparing these splinting choices for the different types of trauma and their effect on (O) healing outcomes for the teeth. A keyword search of PubMed was used. Reference lists from identified articles and dental traumatology texts were also appraised. The inclusion criterion for this review was either a multivariate analysis or controlled stratified analyses as many variables have the potential to confound the assessment and evaluation of healing outcomes for teeth that have been luxated, avulsed or root-fractured. A positive statistical test is not proof of a causal conclusion, as a positive statistical relationship can arise by chance, and so this review also appraises animal studies that reportedly explain biological mechanisms that relate to healing outcomes of splinted teeth. The clinical studies were ranked using the ,Centre of Evidence-based Medicine' categorization (levels 1,5). All 12 clinical studies selected were ranked as level 4. The studies generally indicate that the prognosis is determined by the type of injury rather than factors associated with splinting. The results indicate that the types of splint and the fixation period are generally not significant variables when related to healing outcomes. This appraisal identified difficulties in the design of animal experimentation to correctly simulate some dental injuries. Some of the studies employed rigid splinting techniques, which are not representative of current recommendations. Recommended splinting treatment protocols for teeth that have been luxated, avulsed or root-fractured teeth are formulated on the strength of research evidence. Despite the ranking of these studies in this appraisal as low levels of evidence, these recommendations should be considered ,best practice', a core philosophy of evidence-based dentistry. [source] Post-fire recovery of ant communities in Submediterranean Pinus nigra forestsECOGRAPHY, Issue 2 2006Anselm Rodrigo This study analyzes the variations in the structure and composition of ant communities in burned Pinus nigra forests in central Catalonia (NE Spain). Pinus nigra forests do not recover after fire, changing to shrublands and oak coppices. For this reason, we suggest that ant communities of burned P. nigra forests will change after fire, because the post-fire scenario, in particular with the increase of open areas, is different to the unburned one, and more favourable for some species than for others. In four locations previously occupied by P. nigra forests where different fires occurred 1, 5, 13 and 19 yr before the sampling, we sampled the structure and composition of ant communities with pitfall traps, tree traps and net sweeping in unburned plots and in plots affected by canopy and understory fire. The results obtained suggest that canopy and understory fire had little effect on the structure of ant communities. Thus, many variables concerning ant communities were not modified either by fire type (understory or canopy fire) or by time since fire. However, a number of particular species were affected, either positively or negatively, by canopy fire: three species characteristic of forest habitats decreased after fire, while eight species characteristic of open habitats increased in areas affected by canopy fire, especially in the first few years after fire. These differences in ant community composition between burned and unburned plots imply that the maximum richness is achieved when there is a mixture of unburned forests and areas burned with canopy fire. Moreover, as canopy cover in P. nigra forests burned with canopy fire is not completed in the period of time studied, the presence of the species that are characteristic of burned areas remains along the chronosequence studied, while the species that disappear after fire do not recover in the period of time considered. Overall, the results obtained indicate that there is a persistent replacement of ant species in burned P. nigra forests, as is also the case with vegetation. [source] Factors Associated with the Income Distribution of Full-Time Physicians: A Quantile Regression ApproachHEALTH SERVICES RESEARCH, Issue 5 2007Ya-Chen Tina Shih Objective. Physician income is generally high, but quite variable; hence, physicians have divergent perspectives regarding health policy initiatives and market reforms that could affect their incomes. We investigated factors underlying the distribution of income within the physician population. Data Sources. Full-time physicians (N=10,777) from the restricted version of the 1996,1997 Community Tracking Study Physician Survey (CTS-PS), 1996 Area Resource File, and 1996 health maintenance organization penetration data. Study Design. We conducted separate analyses for primary care physicians (PCPs) and specialists. We employed least square and quantile regression models to examine factors associated with physician incomes at the mean and at various points of the income distribution, respectively. We accounted for the complex survey design for the CTS-PS data using appropriate weighted procedures and explored endogeneity using an instrumental variables method. Principal Findings. We detected widespread and subtle effects of many variables on physician incomes at different points (10th, 25th, 75th, and 90th percentiles) in the distribution that were undetected when employing regression estimations focusing on only the means or medians. Our findings show that the effects of managed care penetration are demonstrable at the mean of specialist incomes, but are more pronounced at higher levels. Conversely, a gender gap in earnings occurs at all levels of income of both PCPs and specialists, but is more pronounced at lower income levels. Conclusions. The quantile regression technique offers an analytical tool to evaluate policy effects beyond the means. A longitudinal application of this approach may enable health policy makers to identify winners and losers among segments of the physician workforce and assess how market dynamics and health policy initiatives affect the overall physician income distribution over various time intervals. [source] A best-evidence synthesis review of the administration of psychotropic pro re nata (PRN) medication in in-patient mental health settingsJOURNAL OF CLINICAL NURSING, Issue 9 2008John A Baker BNurs, MPhil Aims and objectives., This paper aims to synthesise published literature of drug use/administration studies of pro re nata psychotropic medications in mental health wards. Design., The study employed a best-evidence synthesis review design. Background., The administration of psychotropic pro re nata medications is a frequently used clinical intervention in mental health wards. Pro re nata contributes to exposing patients to high doses of antipsychotic medication. Despite the frequent use of pro re nata, there is limited evidence of their effectiveness. Methods., A best-evidence synthesis review. Results., Six major themes emerged from the literature: (i) frequency of administration; (ii) administration during the 24-hour day; (iii) administration associated with length and stage of admission; (iv) rationales for administration; (v) medicines administered (including route of administration); and (vi) effects and side effects of the medicines administered. Conclusions., Overall findings indicate that the administration of psychotropic pro re nata varies radically and appears to be influenced by many variables. Relevance to clinical practice., Patients are most likely to receive a benzodiazepine or typical antipsychotic as pro re nata. Pro re nata is an important and under-researched clinical intervention used in mental health wards. [source] Hematology and blood biochemistry in infant baboons (Papio hamadryas)JOURNAL OF MEDICAL PRIMATOLOGY, Issue 3 2003L.M. Havill Abstract: Although published normative reference standards for hematologic and clinical chemistry measures are available for adult baboons, their applicability to infants has not been addressed. We analyzed these measures in 110 infant baboons (55 females and 55 males) from a large breeding colony at the Southwest Regional Primate Research Center in San Antonio, Texas. The sample consists of olive baboons and olive/yellow baboon hybrids, 1 week to 12 months of age. We produced cross-sectional reference values and examined the effects of age, sex, and subspecies on these variables. Hematology reference ranges for infant baboons are similar to, but wider than, those for adults. Reference ranges for blood biochemistry measures are generally more dissimilar to adults, indicating that for many variables, reference ranges for adult baboons are not adequate for infants. Although sex and subspecies differences are rare, age accounts for more than 10% of the variance in many of the variables. [source] Alcohol is the Main Factor in Excess Traffic Accident Fatalities in FranceALCOHOLISM, Issue 12 2002Michel Reynaud Background The aim of this study was to better evaluate the role of alcohol drinking in fatalities linked to road traffic accidents. Methods The data of accidents were collected by a French official agency from police records, including many variables, among which was a blood alcohol test. They were analyzed in a descriptive way and toward a logistic regression. This exhaustive database comprised all of the 500,961 accidents with casualties that involved less than three vehicles (28,506 fatal accidents) recorded in France during a 52 month period (September 1995 to December 1999). The results of the alcohol tests were known in 78.7 of the drivers. Results The blood alcohol concentration was over the legal limit (0.50 g/L in France) in 9.8% of the accidents with casualties overall. Considering only fatal accidents, the rate of positive alcohol test in drivers was approximately 31.5%. This rate varied depending on the period and the type of accident, raising up to 71.2% in single-vehicle accidents (loss of control) at night during the weekend. The percentage of positive alcohol tests also dramatically increased following the number of fatalities per accident (87.5% in single-vehicle accidents during weekend nights involving three or more killed). The logistic regression in single-vehicle accident shows that the higher odds ratios concern the positive blood alcohol test (OR = 4.19), clearly overwhelming the other precipitating factors of accidents (age of driver, meteorological conditions, time of day, and other factors). Conclusions Drinking alcohol before driving is a well known factor of accidents. We clearly demonstrate here that it is the main factor leading to deaths linked to road traffic accidents in France. The results are strengthened, and some analyses are allowed, by the exceptional features of our database. The authors emphasize the need for prevention measures. [source] Toward a predictive model of patient satisfaction with nurse practitioner careJOURNAL OF THE AMERICAN ACADEMY OF NURSE PRACTITIONERS, Issue 4 2005A/G/FNP, Ann Green PhD Purpose (a) To determine if caring behaviors of nurse practitioners (NPs), gender of NPs, setting (urban or rural), and age, gender, ethnicity, education, and income of patients were predictors of patient satisfaction; (b) to determine which of these characteristics was the best predictor(s) of patient satisfaction; and (c) begin to develop a conceptual model for explaining patient satisfaction with NP care. Data sources Responses to the Caring Behaviors Inventory (CBI) and a demographic inquiry by 348 NPs in Louisiana and completion of the Di'Tomasso,Willard Patient Satisfaction Questionnaire (DWPSQ) and a demographic inquiry from 817 patients in Louisiana served as data sources. A predictive modeling design explored which variable(s) is the best predictor of patient satisfaction, and multiple regression was used to determine the equation for the best-fitting line and the optimal model for the best predictor(s) of patient satisfaction. Conclusions CBI mean scores were high for all NPs. No statistically significant difference was found between male NPs' and female NPs' total mean CBI scores and between urban or rural total mean CBI scores. DWPSQ mean scores and subscale scores indicated high satisfaction with NP care. No statistically significant relationships were found between the NPs' CBI mean scores and the patients' DWPSQ mean scores. There were significant relationships between the DWPSQ subscales, including Wait Time and Patient Management. Stepwise linear regression revealed that patients' age group was a predictor of DWPSQ total mean scores. Implications for practice NPs need to be aware of developmental differences in all age groups and the differences in perceptions of care. There are many variables to consider when determining patient satisfaction with care, including the patients' sociodemographic and health variables, the healthcare system, and characteristics of the healthcare providers. Awareness of these variables may affect how NPs deliver care and ensure quality care with which the patients are satisfied. [source] Electrophysiological mapping for the implantation of deep brain stimulators for Parkinson's disease and tremorMOVEMENT DISORDERS, Issue S14 2006Robert E. Gross MD Abstract The vast majority of centers use electrophysiological mapping techniques to finalize target selection during the implantation of deep brain stimulation (DBS) leads for the treatment of Parkinson's disease and tremor. This review discusses the techniques used for physiological mapping and addresses the questions of how various mapping strategies modify target selection and outcome following subthalamic nucleus (STN), globus pallidus internus (GPi), and ventralis intermedius (Vim) deep brain stimulation. Mapping strategies vary greatly across centers, but can be broadly categorized into those that use microelectrode or semimicroelectrode techniques to optimize position prior to implantation and macrostimulation through a macroelectrode or the DBS lead, and those that rely solely on macrostimulation and its threshold for clinical effects (benefits and side effects). Microelectrode criteria for implantation into the STN or GPi include length of the nucleus recorded, presence of movement-responsive neurons, and/or distance from the borders with adjacent structures. However, the threshold for the production of clinical benefits relative to side effects is, in most centers, the final, and sometimes only, determinant of DBS electrode position. Macrostimulation techniques for mapping, the utility of microelectrode mapping is reflected in its modification of electrode position in 17% to 87% of patients undergoing STN DBS, with average target adjustments of 1 to 4 mm. Nevertheless, with the absence of class I data, and in consideration of the large number of variables that impact clinical outcome, it is not possible to conclude that one technique is superior to the other in so far as motor Unified Parkinson's Disease Rating Scale outcome is concerned. Moreover, mapping technique is only one out of many variables that determine the outcome. The increase in surgical risk of intracranial hemorrhage correlated to the number of microelectrode trajectories must be considered against the risk of suboptimal benefits related to omission of this technique. © 2006 Movement Disorder Society [source] Design and analysis for the Gaussian process model,QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 5 2009Bradley Jones Abstract In an effort to speed the development of new products and processes, many companies are turning to computer simulations to avoid the time and expense of building prototypes. These computer simulations are often complex, taking hours to complete one run. If there are many variables affecting the results of the simulation, then it makes sense to design an experiment to gain the most information possible from a limited number of computer simulation runs. The researcher can use the results of these runs to build a surrogate model of the computer simulation model. The absence of noise is the key difference between computer simulation experiments and experiments in the real world. Since there is no variability in the results of computer experiments, optimal designs, which are based on reducing the variance of some statistic, have questionable utility. Replication, usually a ,good thing', is clearly undesirable in computer experiments. Thus, a new approach to experimentation is necessary. Published in 2009 by John Wiley & Sons, Ltd. [source] What to Do about Missing Values in Time-Series Cross-Section DataAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 2 2010James Honaker Applications of modern methods for analyzing data with missing values, based primarily on multiple imputation, have in the last half-decade become common in American politics and political behavior. Scholars in this subset of political science have thus increasingly avoided the biases and inefficiencies caused by ad hoc methods like listwise deletion and best guess imputation. However, researchers in much of comparative politics and international relations, and others with similar data, have been unable to do the same because the best available imputation methods work poorly with the time-series cross-section data structures common in these fields. We attempt to rectify this situation with three related developments. First, we build a multiple imputation model that allows smooth time trends, shifts across cross-sectional units, and correlations over time and space, resulting in far more accurate imputations. Second, we enable analysts to incorporate knowledge from area studies experts via priors on individual missing cell values, rather than on difficult-to-interpret model parameters. Third, because these tasks could not be accomplished within existing imputation algorithms, in that they cannot handle as many variables as needed even in the simpler cross-sectional data for which they were designed, we also develop a new algorithm that substantially expands the range of computationally feasible data types and sizes for which multiple imputation can be used. These developments also make it possible to implement the methods introduced here in freely available open source software that is considerably more reliable than existing algorithms. [source] Socio-economic gradients in self-reported diabetes for Indigenous and non-Indigenous Australians aged 18,64AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 2010Joan Cunningham Abstract Objective: To examine and compare socio-economic gradients in diabetes among Indigenous and non-Indigenous Australians. Methods: I analysed weighted data on self-reported diabetes and a range of socio-economic status (SES) measures for 5,417 Indigenous and 15,432 non-Indigenous adults aged 18,64 years from two nationally representative surveys conducted in parallel by the Australian Bureau of Statistics in 2004,05. Results: After adjusting for age, diabetes prevalence was significantly higher among those of lower SES in both Indigenous and non-Indigenous populations. The age- and sex-adjusted odds ratios (OR) for diabetes for the lowest versus the highest SES group were similar for the two populations on many variables. For example, the OR for the lowest quintile of equivalised household income (compared with quintiles 3,5 combined) was 2.3 (95% CI 1.6,3.4) for the Indigenous population and 2.0 (95% CI 1.5,2.8) for the non-Indigenous population. However, Indigenous people of high SES had greater diabetes prevalence than low SES non-Indigenous people on every SES measure examined. Conclusion: Socio-economic status explains some but not all of the difference in diabetes prevalence between Indigenous and non-Indigenous Australians. Other factors that may operate across the socio-economic spectrum, such as racism, stress, loss and grief, may also be relevant and warrant further examination. Implications: Indigenous Australians do not constitute a homogeneous group with respect to socio-economic status or diabetes prevalence, and this diversity must be recognised in developing measures to redress Indigenous health disadvantage. [source] Ultra scale-down studies of the effect of flow and impact conditions during E. coli cell processingBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2006G. Chan Abstract The ability to recover cells from a fermentation broth in an intact form can be an important criterion for determining the overall performance of a recovery and purification sequence. Disruption of the cells can lead to undesired contamination of an extracellular product with intracellular components and vice versa loss of intracellular products may occur. In particular, the value of directed location of a product in the periplasmic space of say Escherichia coli (E. coli) would be diminished by such premature non-selective cell disruption. Several options exist for cell recovery/removal; namely centrifugation, in batch or continuous configuration, filtration or membrane operations, and in selected cases expanded beds. The choice of operation is dependant on many variables including the impact on the overall process sequence. In all cases, the cells are exposed to shear stresses of varying levels and times and additionally such environments exist in ancillary operations such as pumping, pipe flow, and control valves. In this study, a small-scale device has been designed to expose cells to controlled levels of shear, time and impact in a way that seeks to mimic those effects that may occur during full-scale processes. The extent of cell breakage was found to be proportional to shear stress. An additional level of breakage occurred due to the jet impacting on the collecting surface. Here it was possible to correlate the additional breakage with the impact velocity, which is a function of the distance that the jet travels before meeting the collection surface and the initial jet velocity. © 2006 Wiley Periodicals, Inc. [source] Fine-scale Microhabitat Heterogeneity in a French Guianan ForestBIOTROPICA, Issue 4 2010Christopher Baraloto ABSTRACT We examined fine-scale heterogeneity of environmental conditions in a primary rain forest in French Guiana to describe variation in microhabitats that plants may experience during establishment. We characterized both the range as well as the spatial structuring of 11 environmental factors important for seedling establishment in six hexagonal sampling grids, one each in gap and understory sites at three points representing the predominant geomorphic units in this primary forest. Each grid contained 37 sampling points separated by 31 cm,20 m. Monte-Carlo tests of semivariograms against complete spatial randomness indicated that for many variables in all six sampling grids, spatial dependence did not exceed 1 m. A principal component analysis of all sampling points revealed a lack of spatial microhabitat structure, rather than homogeneous patches associated with canopy structure or geomorphology. Our results suggest that ample fine-scale spatial heterogeneity exists to support the coexistence of plant species with differential abiotic requirements for regeneration. [source] The prevalence and predictors of erectile dysfunction in men with newly diagnosed with type 2 diabetes mellitusBJU INTERNATIONAL, Issue 1 2007Adel Al-Hunayan OBJECTIVE To determine the prevalence of and risk factors for erectile dysfunction (ED) in men newly diagnosed with type 2 diabetes mellitus (DM). PATIENTS AND METHODS All consecutive samples of men newly diagnosed with type 2 DM attending the diabetes centre in the capital of Kuwait were included in the study. Face-to-face interviews with the men were conducted using the International Index of Erectile Function (IIEF)-5 questionnaire. A threshold IIEF-5 score of <21 was used to identify men with ED. Pertinent clinical and laboratory characteristics were collected. RESULTS Of 323 men with newly diagnosed type 2 DM, 31% had ED; comparing potent men and men with ED, there were statistically significant differences for smoking, duration of smoking, hypertension, education level, body mass index and serum glycosylated haemoglobin level. Among these, age was the most important risk factor identified by multivariate logistic regression. CONCLUSION About a third of men with newly diagnosed type 2 DM had ED; this was associated with many variables, but most notably with age at presentation. [source] Multi-dimensional phenotyping: towards a new taxonomy for airway diseaseCLINICAL & EXPERIMENTAL ALLERGY, Issue 10 2005A. J. Wardlaw Summary All the real knowledge which we possess, depends on methods by which we distinguish the similar from the dissimilar. The greater the number of natural distinctions this method comprehends the clearer becomes our idea of things. The more numerous the objects which employ our attention the more difficult it becomes to form such a method and the more necessary. [1]. Classification is a fundamental part of medicine. Diseases are often categorized according to pre-20th century descriptions and concepts of disease based on symptoms, signs and functional abnormalities rather than on underlying pathogenesis. Where the aetiology of disease has been revealed (for example in the infectious diseases) a more precise classification has become possible, but in the chronic inflammatory diseases, and in the inflammatory airway diseases in particular, where pathogenesis has been stubbornly difficult to elucidate, we still use broad descriptive terms such as asthma and chronic obstructive pulmonary disease, which defy precise definition because they encompass a wide spectrum of presentations and physiological and cellular abnormalities. It is our contention that these broad-brush terms have outlived their usefulness and that we should be looking to create a new taxonomy of airway disease,a taxonomy that more closely reflects the spectrum of phenotypes that are encompassed within the term airway inflammatory diseases, and that gives full recognition to late 20th and 21st century insights into the disordered physiology and cell biology that characterizes these conditions in the expectation that these will map more closely to both aetiology and response to treatment. Development of this taxonomy will require a much more complete and sophisticated correlation of the many variables that make up a condition than has been usual to employ in an approach that encompasses multi-dimensional phenotyping and uses complex statistical tools such as cluster analysis. [source] | |||||||||||||