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Critical Variables (critical + variable)
Selected AbstractsApplication of Regression-Discontinuity Analysis in Pharmaceutical Health Services ResearchHEALTH SERVICES RESEARCH, Issue 2 2006Ilene H. Zuckerman Objective. To demonstrate how a relatively underused design, regression-discontinuity (RD), can provide robust estimates of intervention effects when stronger designs are impossible to implement. Data Sources/Study Setting. Administrative claims from a Mid-Atlantic state Medicaid program were used to evaluate the effectiveness of an educational drug utilization review intervention. Study Design. Quasi-experimental design. Data Collection/Extraction Methods. A drug utilization review study was conducted to evaluate a letter intervention to physicians treating Medicaid children with potentially excessive use of short-acting ,2 -agonist inhalers (SAB). The outcome measure is change in seasonally-adjusted SAB use 5 months pre- and postintervention. To determine if the intervention reduced monthly SAB utilization, results from an RD analysis are compared to findings from a pretest,posttest design using repeated-measure ANOVA. Principal Findings. Both analyses indicated that the intervention significantly reduced SAB use among the high users. Average monthly SAB use declined by 0.9 canisters per month (p<.001) according to the repeated-measure ANOVA and by 0.2 canisters per month (p<.001) from RD analysis. Conclusions. Regression-discontinuity design is a useful quasi-experimental methodology that has significant advantages in internal validity compared to other pre,post designs when assessing interventions in which subjects' assignment is based on cutoff scores for a critical variable. [source] Different behavioral effects of neurotoxic dorsal hippocampal lesions placed under either isoflurane or propofol anesthesiaHIPPOCAMPUS, Issue 3 2008Mark G. Baxter Abstract Anesthetic protocols for behavioral neuroscience experiments are evolving as new anesthetics are developed and surgical procedures are refined to improve animal welfare. We tested whether neurotoxic dorsal hippocampal lesions produced under two different anesthetic protocols would have different behavioral and/or histo-pathological effects. Rats were anesthetized with either propofol, an intravenous anesthetic, or isoflurane, a gaseous anesthetic, and multiple injections of an excitotoxin (N -methyl- D -aspartate) were stereotaxically placed in the dorsal hippocampus bilaterally. Intraoperative physiological parameters were similar in the two surgical groups, as were the volumes of the lesions, although the profile of postoperative impairment in a spatial learning task differed between the lesion groups depending on the anesthetic regimen used. These results show that the choice of anesthetic protocol is a critical variable in designing behavioral neuroscience experiments using neurosurgical procedures. This factor should be considered carefully in experimental design and in cross-study comparisons of lesion effects on behavior. © 2007 Wiley-Liss, Inc. [source] A New Paradigm for Clinical Investigation of Infectious Syndromes in Older Adults: Assessing Functional Status as a Risk Factor and Outcome MeasureJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2005Kevin High Abstract Adults aged 65 and over comprise the fastest growing segment of the U.S. population, and older adults experience greater morbidity and mortality due to infection than young adults. While this factor is well established, most clinical investigation of infectious diseases in the aged focuses on microbiology, and crude endpoints of clinical success such as cure rates or mortality, but often fails to assess functional status, a critical variable in geriatric care. Functional status can be evaluated as a risk factor for infectious disease or an outcome of interest following specific interventions utilizing well-validated instruments. This paper outlines the currently available data suggesting a link between infection, immunity and impaired functional status in the elderly, summarizes commonly employed instruments used to determine specific aspects of functional status, and provides recommendations for a new paradigm in which clinical trials of older adults include functional assessment. [source] Optimization of the ESI and APCI experimental variables for the LC/MS determination of s-triazines, methylcarbamates, organophosphorous, benzimidazoles, carboxamide and phenylurea compounds in orange samplesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2007Guilherme M. Titato Abstract In this work, ten selected pesticides of different chemical groups, indicated to orange culture, were extracted and determined by liquid chromatography,mass spectrometry using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) operating in the positive ion detection mode. Applying a variables selection technique verified that cone voltage, source temperature and drying-gas flow-rate are the critical variables when the ESI was used, while cone voltage was found to be the only critical variable for the MS system, operating with the APCI ionization mode. After optimization of the most important parameters through the variables selection technique, the selected ion-recording (SIR) mode, monitoring the [M + H]+ species for all the compounds, was applied for the method validation of the pesticides, in both ionization modes. In orange samples, matrix effects did not interfere with the determination of the pesticides. Pesticides quantification limits ranged from 10 to 50 µg kg,1 for ESI and from 8.2 to 45 µg kg,1 for APCI. Linearity was studied from LOQ upto 200 times LOQ values (r > 0.98). Recoveries obtained were in the range of 70.2,100.5% (RSDs less than 10%). In order to guarantee that the identification and confirmation of the studied pesticides in real samples were unequivocal, characteristic fragment ions of the pesticides were obtained by varying the cone voltage (in-source CID). Copyright © 2007 John Wiley & Sons, Ltd. [source] Higher Cost, Lower Validity and Higher Utility: Comparing the Utilities of Two Tests that Differ in Validity, Costs and SelectivityINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 2 2000George C. Thornton Traditional approaches to comparing the utility of two tests have not systematically considered the effects of different levels of selectivity that are feasible and appropriate in various selection situations. For example, employers who hope to avoid adverse impact often find they can be more selective with some tests than with others. We conducted two studies to compare the utilities of two tests that differ in costs, validity, and feasible levels of selectivity which can be employed. First, an analytical solution was conducted starting with a standard formula for utility. This analysis showed that for both fixed and variable hiring costs, a higher-cost, lower-validity procedure can have higher utility than a lower-cost, higher-validity procedure when the selection ratios permissible using the two procedures are sufficiently (yet realistically) different. Second, using a computer simulation method, several combinations of the critical variables were varied systematically to detect the limits of this effect in a finite set of specific selection situations. The results showed that the existence of more severe levels of adverse impact greatly reduced the utility of a written test with relatively high validity and low cost in comparison with an assessment center with lower validity and higher cost. Both studies showed that the consideration of selectivity can yield surprising conclusions about the comparative utility of two tests. Even if one test has lower validity and higher cost than a second test, the first may yield higher utility if it allows the organization to exercise stricter levels of selectivity. [source] Estimating the effectiveness of a rotational irrigation delivery system: A case study from Pakistan,IRRIGATION AND DRAINAGE, Issue 3 2010Noor ul Hassan Zardari warabandi; allocation de l'eau; bassin de l'Indus; Pakistan Abstract In this study, basic principles of the rotational irrigation water delivery system of Pakistan (i.e. the warabandi) and the performance of the warabandi system under current socio-economic conditions have been investigated from a farmers' survey completed from 154 farmers located on five watercourses of the lower Indus River Basin. It is shown that irrigation water allocation based on very limited criteria does not give much incentive to the farmers for improving agricultural income. Also, the survey results suggest that the productivity of limited irrigation water could not be maximized under the warabandi system. We have therefore suggested the basic principles of the warabandi system should be revised by making them suitable for the current socio-economic conditions. We propose that the existence or non-existence of fresh groundwater resources along with other critical variables should be taken into consideration when making canal water allocation decisions. A framework to allow distribution equity and efficiency in water allocations , such as considering the gross area of a tertiary canal, sensitivity of crop growth stage to water shortage, crop value, bias of allocation towards most water use efficient areas, the potential losses from water deficiency, etc. , should be developed as a tool to improve water productivity for Pakistan and for individual farmers. The contribution of groundwater in the farmers' income from agriculture and the economic value of irrigation water have also been estimated. Copyright © 2009 John Wiley & Sons, Ltd. Cette étude analyse les principes de base et la performance du tour d'eau (le warabandi) selon les conditions socio-économiques à partir d'une enquête auprès de 154 agriculteurs situés sur cinq cours d'eau du bassin inférieur de l'Indus. Il est montré que la répartition de l'eau d'irrigation basée sur peu de critères n'incite pas les agriculteurs à améliorer leurs revenus. En outre, les résultats de l'enquête suggèrent que la productivité de l'eau rare ne peut pas être améliorée dans le cadre du système warabandi. Nous avons donc proposé que les principes de base du warabandi soient révisés de façon à les adapter à la situation socio-économique actuelle. Nous proposons que la disponibilité en eaux souterraines ainsi que d'autres variables soient prises en compte dans les décisions d'allocation. Un cadre permettant une allocation de l'eau équitable et efficace , prenant en compte la surface brute commandée par un canal tertiaire, la sensibilité de la croissance des cultures au moment de la pénurie d'eau, la valeur de la récolte, l'orientation vers les zones valorisant le mieux l'eau, les pertes dues au déficit en eau, etc. , devrait être développé comme un outil pour améliorer la productivité de l'eau pour le Pakistan et pour les agriculteurs. La contribution des eaux souterraines au revenu des irrigants et la valeur économique de l'eau ont également été estimées. Copyright © 2009 John Wiley & Sons, Ltd. [source] Optimization of the ESI and APCI experimental variables for the LC/MS determination of s-triazines, methylcarbamates, organophosphorous, benzimidazoles, carboxamide and phenylurea compounds in orange samplesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2007Guilherme M. Titato Abstract In this work, ten selected pesticides of different chemical groups, indicated to orange culture, were extracted and determined by liquid chromatography,mass spectrometry using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) operating in the positive ion detection mode. Applying a variables selection technique verified that cone voltage, source temperature and drying-gas flow-rate are the critical variables when the ESI was used, while cone voltage was found to be the only critical variable for the MS system, operating with the APCI ionization mode. After optimization of the most important parameters through the variables selection technique, the selected ion-recording (SIR) mode, monitoring the [M + H]+ species for all the compounds, was applied for the method validation of the pesticides, in both ionization modes. In orange samples, matrix effects did not interfere with the determination of the pesticides. Pesticides quantification limits ranged from 10 to 50 µg kg,1 for ESI and from 8.2 to 45 µg kg,1 for APCI. Linearity was studied from LOQ upto 200 times LOQ values (r > 0.98). Recoveries obtained were in the range of 70.2,100.5% (RSDs less than 10%). In order to guarantee that the identification and confirmation of the studied pesticides in real samples were unequivocal, characteristic fragment ions of the pesticides were obtained by varying the cone voltage (in-source CID). Copyright © 2007 John Wiley & Sons, Ltd. [source] Immediate effects of prescribed burning, chopping and clearing on runoff, infiltration and erosion in a shrubland area in Galicia (NW Spain)LAND DEGRADATION AND DEVELOPMENT, Issue 5 2008C. Fernández Abstract The immediate effects of three different fuel management treatments on runoff, infiltration and erosion were evaluated in a mixed heathland in Galicia (NW Spain). The treatments compared were: prescribed burning, shrub chopping and shrub clearing. Rainfall simulations were conducted immediately before and after fuel reduction treatments. A rainfall rate of 67,mm,h,1 was applied for 30,min to each runoff plot. Application of treatments significantly affected runoff and infiltration, but the parameter most affected by treatment was soil erosion, especially after prescribed burning. However, sediment yields measured immediately after treatments were low in all the cases, varying from 32,kg,ha,1 after shrub clearing to 248,kg,ha,1 after prescribed burning. In the rainfall simulation plots subjected to prescribed burning, the maximum temperatures reached at mineral soil surface during burns significantly affected soil losses. The organic layer remaining after treatments and soil moisture contents appeared to be critical variables in controlling runoff and erosion during the first rainfall event following fuel reduction treatments. When the remaining organic layer was removed just after treatments and a new rainfall simulation was carried out, mean infiltration rate trended to decrease and cumulative runoff and sediment yield tended to increase. The above information could be useful for determining whether fuel management prescriptions are compatible with fire hazard reduction and soil conservation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Variables Affecting the Participation in Individual DevelopmentPERFORMANCE IMPROVEMENT QUARTERLY, Issue 4 2001Janet L. Polach ABSTRACT Workers across the country are being asked to acquire more information at an increasing rate in response to technological, structural, and new product and process changes occurring in the workplace. Organizations continue to struggle with understanding the capabilities and capacity of their workforce and are making critical investments in building expertise. But how do organizations engage people in this development effort? This paper proposes three critical variables that affect an individual's participation in the development process. Proposed variables are: 1) individual expertise, 2) system stability, and 3) the acceptance for the need for improvement. The paper reviews the theories that support the proposed variables in terms of influencing learning participation, and it concludes by pointing out implications for human development practitioners. It identifies where further research is needed in gaining greater insight into understanding this complex issue. [source] Application of the operating window concept to remediation-option selectionREMEDIATION, Issue 3 2004Duncan I. Scott An Erratum has been published for this article in Remediation 14(4) 2004, 141. The selection of remediation options for the management of unacceptable risks at contaminated sites is hindered by insufficient information on their performance under different site conditions. Therefore, there is a need to define "operating windows" for individual remediation options to summarize their performance under a variety of site conditions. The concept of the "operating window" has been applied as both a performance optimization tool and decision support tool in a number of different industries. Remediation-option operating windows could be used as decision support tools during the "options appraisal" stage of the Model Procedures (CLR 11), proposed by the Environment Agency (EA) for England and Wales, to enhance the identification of "feasible remediation options" for "relevant pollutant linkages." The development of remediation-option operating windows involves: 1) the determination of relationships between site conditions ("critical variables") and option performance parameters (e.g., contaminant degradation or removal rates) and 2) the identification of upper- and lower-limit values ("operational limits") for these variables that define the ranges of site conditions over which option performance is likely to be sufficient (the "operating window") and insufficient (the "operating wall") for managing risk. Some research has used case study data to determine relationships between critical variables and subsurface natural attenuation (NA) process rates. Despite the various challenges associated with the approach, these studies suggest that available case study data can be used to develop operating windows for monitored natural attenuation (MNA) and, indeed, other remediation options. It is envisaged that the development of remediation-option operating windows will encourage the application of more innovative remediation options as opposed to excavation and disposal to landfill and/or on-site containment, which remain the most commonly employed options in many countries. © 2004 Wiley Periodicals, Inc. [source] | ||||||||||||||||