Curve Methodology Research Articles

Associative and non-associative fentanyl tolerance in the rat: evaluation of cross tolerance with mu-and kappa-specific opioids.

Associative tolerance to the analgesic effects of morphine is most pronounced when morphine is paired with a distinctive context at a long interdose interval (IDI). In contrast, morphine administered at a short IDI promotes the development of non-associative tolerance and disrupts the acquisition of associative tolerance. The impact of IDI on the development of associative tolerance to opioids other than morphine has not been investigated previously. This research examined associative and non-associative tolerance to the analgesic effects of fentanyl in rats. Cross tolerance for these two forms of tolerance with morphine (mureceptor agonist) and U50,488H (kappa-receptor agonist) analgesia was also investigated. Animals were given eight fentanyl injections (0.10 mg/kg) paired or unpaired with a distinctive context at either a 3-h (short) or 96-h (long) IDI. Subjects were then tested for tolerance in the distinctive context using the tail-flick procedure and dose-response curve methodology. At the short IDI, animals developed non-associative tolerance to fentanyl that was receptor specific, i.e., cross tolerant with morphine analgesia but not with U50,488H analgesia. At the long IDI, fentanyl-tested animals displayed tolerance that appeared to be controlled primarily by associative processes. This associative form of tolerance was also receptor specific, displaying cross tolerance with morphine but not with U50,488H. The impact of IDI on the development of non-associative and associative fentanyl tolerance is consistent with findings obtained with morphine showing that conditions conducive to the development of non-associative tolerance disrupt the acquisition of associative tolerance. The cross-tolerance data, however, did not parallel previous research examining the cross-tolerance profiles of associative and non-associative morphine tolerance.

Iron bioavailability from hemoglobin and hemin in chick, rat, cat, and dog: A comparative study

Experiments were conducted, using hemoglobin concentration, hematocrit and total body gain in hemoglobin, to assess iron bioavailability from dietary hemoglobin and hemin across several species. Iron bioavailability was determined by adding hemoglobin and hemin to casein-dextrose basal diets to provide iron within the linear response range for each species. Similar diets were fed to all species with the exception that the cat diet contained 25% poultry fat to improve acceptability and growth whereas 3% corn oil was used in chick, rat, and dog diets. Percent bioavailability relative to ferrous sulfate-iron was calculated using standard curve methodology in chick, cat, and dog assays, and slope-ratio methodology in the rat assay. In species that were less homogeneous in size, i.e., cats and dogs, both initial and final body weights varied considerably, therefore estimates based on total body gain in hemoglobin were deemed to be more accurate estimates of iron bioavailability. Hemin was poorly available to rats but completely unavailable to chicks, cats and dogs. Hemoglobin iron bioavailability was 68% for rats, 93% for chicks, 90% for dogs, and 70% for cats. The protein portion of the hemoglobin molecule is hypothesized to play a critical role in heme iron absorption from a casein dextrose based diet in these species.

THE SUBSTANTIVE NATURE OF PERFORMANCE VARIABILITY: PREDICTING INTERINDIVIDUAL DIFFERENCES IN INTRAINDIVIDUAL PERFORMANCE

The nature of intraindividual performance variability over time, along with individual difference predictors of such variability, was examined using latent growth curve methodology. Quarterly sales performance for a sample of securities analysts (n= 303) was measured at 8 times. Average intraindividual performance approximated a basic “learning” curve, although there were considerable individual differences in each of the latent performance growth parameters. Individual difference predictors from a biodata inventory were moderately related to these latent growth parameters. Theoretical and practical implications of performance variability for personnel selection are also discussed.

Estimating the Income Elasticity of Demand for Housing: A Comparison of Traditional and Lorenz-Concentration Curve Methodologies

This paper provides a comparative analysis of traditional and Lorenz concentration curve (LC) approaches to estimating the income elasticity of demand for housing. Using data from the 1989 American Housing Survey, we compare LC results with those obtained from a traditional model in which tenure choice and housing demand are jointly determined, and which includes non-income determinants of demand. The comparison is intended to provide researchers with information concerning specific differences in empirical results obtained using the two approaches.

Discussion

This article demonstrates a latent growth curve methodology for analyzing longitudinal data of adolescent substance use. Hypotheses concerning the form of growth in alcohol, cigarette, and marijuana use, and covariates influencing the form of growth, were tested. Participants were male and female adolescents (n=664) assessed at three time points. A common trajectory existed across the developmental period with significant increases in all three substances. Second-order multivariate extensions of the basic latent growth modeling framework suggested that associations among the individual differences parameters, representing growth or change in the various substance use behaviors, could be adequately modeled by a higher-order substance use construct. Inept parental monitoring, parent-child conflict, peer deviance, academic failure, gender, and age, were significant predictors of initial levels and the trajectory of substance use.

Contributions of the social context to the development of adolescent substance use: a multivariate latent growth modeling approach

This article demonstrates a latent growth curve methodology for analyzing longitudinal data of adolescent substance use. Hypotheses concerning the form of growth in alcohol, cigarette, and marijuana use, and covariates influencing the form of growth, were tested. Participants were male and female adolescents ( n=664) assessed at three time points. A common trajectory existed across the developmental period with significant increases in all three substances. Second-order multivariate extensions of the basic latent growth modeling framework suggested that associations among the individual differences parameters, representing growth or change in the various substance use behaviors, could be adequately modeled by a higher-order substance use construct. Inept parental monitoring, parent-child conflict, peer deviance, academic failure, gender, and age, were significant predictors of initial levels and the trajectory of substance use.

A comparison of model‐ and multiple imputation‐based approaches to longitudinal analyses with partial missingness

Longitudinal data sets typically suffer from attrition and other forms of missing data. Omissions, attrition, and planned missingness have limited our ability to conduct the most appropriate analyses. When this common problem occurs, several researchers have demonstrated that correct estimation with missing data can be obtained under mild assumptions concerning the missing data mechanism. An example application of latent growth curve methodology, analyzing the longitudinal developmental change in adolescent alcohol consumption, is presented (N = 586; 250 young men and 336 young women, 14 to 16 years of age at the initial time point). The analyses are conducted within a cohort‐sequential design, incorporating missingness introduced by design and due to attrition. We describe and illustrate 3 approaches to the analysis of missing data when some data are missing: multiple‐sample structural equation modeling procedures, raw maximum likelihood analyses, and multiple modeling and data augmentation algorithms.

Unsignaled morphine delivery does not disrupt the development of associative morphine tolerance in the rat

When morphine administration is paired with a distinctive context, tolerance to morphine's analgesic effects comes readily under the associative control of the drug-paired context. These associative tolerance effects are eliminated when a relatively short (i.e., 6 h) interdose interval (IDI) is used for conditioning. Contemporary models of learned tolerance explain the absence of learning at short IDIs by positing that residual morphine effects from a recent drug exposure disrupt the formation of drug-context associations. The present studies examined the impact of Unsignaled morphine injections given 6 h prior to drug-context pairings on the development of associative tolerance. Analgesia was measured by the tail-flick method, and tolerance levels were assessed by dose-response curve methodology. Morphine preexposure had no detectable influence on the acquisition of associative tolerance when rats were tested immediately after conditioning, after a 30-day rest interval, or after a 30-day period of daily saline injections in their home-cage environment. These data suggest disruption of associative tolerance effects at short IDIs is not attributable to residual effects of morphine from the immediately preceding trial.

Summary receiver operating characteristic curves as a technique for meta-analysis of the diagnostic performance of duplex ultrasonography in peripheral arterial disease.

We summarized and compared the diagnostic performance of duplex and color-guided duplex ultrasonography in the evaluation of peripheral arterial disease. We present our research as an example of the use of summary receiver operating characteristic (ROC) curves in a meta-analysis of diagnostic test data. A search of the English-language medical literature published between 1984 and 1994 retrieved 48 reports, 14 of which met the inclusion criteria. The analysis was limited to the aortoiliac and femoropopliteal segments because only two studies reported results of infrapopliteal arteries. Diagnostic performance of duplex and color-guided duplex, defined as the ability to detect a stenosis of 50-99% or an occlusion, was compared using summary ROC curve methodology. This method takes into account heterogeneity across studies attributable to differences in the threshold values used. The summary ROC curves demonstrated a high level of diagnostic performance for both types of duplex imaging, with color-guided duplex scanning being superior (p = .022). For example, at a false-positive rate of .05 (specificity = .95), the analysis predicted a true-positive rate (sensitivity) of .83 for duplex alone and .93 for color guided duplex. Differences in the case mix of the study population and study design did not affect the results. Furthermore, sensitivity analysis did not reveal a strong effect of any single study on the results. For aortoiliac and femoropopliteal arteries, the addition of color flow imaging to duplex scanning improves diagnostic performance in evaluating peripheral arterial disease.

The role of parents and older siblings in predicting adolescent substance use: Modeling development via structural equation latent growth methodology.

Using latent growth curve methodology, this study investigated developmental trends in adolescent, parent, and older sibling substance use across a 3-year period and the predictive effect of these trends on adolescent substance use 2 years later. Participants were 101 adolescents (50 boys and 51 girls) who were an average of 12.34 years old at the first assessment, their parents, and an older sibling. Results indicate that although both parents and siblings contribute to the level of adolescent use, only siblings appear to contribute to the adolescents' subsequent substance use development. The adolescents' developmental trajectory was the best predictor of later use, but siblings contributed to later use indirectly through their influence on adolescents' substance use development. Findings discuss the role of sibling and parent substance use on adolescent substance use and emphasize the utility of latent growth modeling in the study of developmental change.

A multivariate latent growth curve analysis of adolescent substance use

This article demonstrates a multivariate latent growth curve methodology (LGM) for analyzing longitudinal adolescent substance use data. Hypotheses concerning the form of growth in substance use, individual differences in the common trajectory over time, and covariates influencing growth were tested. Significant linear increases existed for alcohol, cigarette, and marijuana use. Second‐order multivariate extensions of LGM indicated that associations among the individual differences parameters of the various substances could be adequately modeled by a higher order substance use construct. Family status, parent‐child conflict, peer encouragement for substance use, parent substance use, and age significantly influenced initial levels of use. Peer encouragement, change in peer encouragement, change in parent‐child conflict, age, and gender significantly influenced development of use. These findings support the influence of families and peers on the development of adolescent substance use and demonstrate the u...

Characterization of the dynamic properties of viscoelastic elements by the direct stiffness and master curve methodologies, part 1: design of load frame and fixtures

The theoretical foundations and principles governing the design of the test fixtures, including the load frame, for use in conjunction with the direct complex stiffness test method for the characterization of the dynamic properties of viscoelastic elements are presented. A graphical approach for facilitating the design and/or evaluation of the static stiffness and fundamental resonance frequency characteristics of the load frame is developed and its use illustrated. Based on an approximate analytical model of the complex stiffness test system comprising the load frame, force transducer, test sample end plates, connecting rods and a viscoelastic element, expressions are derived for correcting the inherent systematic errors in the measured complex stiffness of the viscoelastic element arising from the stiffness and inertia of these fixtures. It is shown that, for errors of less than 5% between the true complex stiffness of a viscoelastic element and the uncorrected measured stiffness, the stiffness of any of the test fixtures should be greater than the highest stiffness of the viscoelastic element by a factor of about 100, over the test frequency range.

Modeling the processes of development via latent variable growth curve methodology

Recent advances in statistical methodology, in particular, latent growth modeling, allow for the testing of complex models regarding developmental trends from both an inter‐ and intraindividual perspective. An example application of latent growth curve methodology, analyzing the effects of gender and parental monitoring on developmental change in adolescent alcohol consumption, is presented. Furthermore, the analyses are conducted within a cohort‐sequential design, incorporating an approach to the analysis of missing data due to attrition. Findings are discussed with particular reference to the utility of latent growth curve models for assessing developmental processes at both the inter‐and intraindividual level across a variety of behavioral domains.

Scaling, optimization and design considerations of electrostatic discharge protection circuits in CMOS technology

The effect of scaling on electrostatic discharge (ESD) robustness in 1.2 to 0.25 μm channel length CMOS technologies is explored for ESD protection circuits and MOSFET structures. Results show that ESD robustness decreases as ESD structures are scaled to smaller dimensions in future technologies. Technology benchmarking, using a standardized ESD design, for evaluating ESD robustness is discussed. The ESD sensitivity of ESD designs to geometrical and semiconductor process parameters are evaluated. An analytical development for electro-thermal failure is developed based on electro quasi-static and adiabatic assumptions. ESD scaling relationships are developed applying MOSFET constant electric field scaling theory. ESD robustness scales as 1/α 3 2 , where α is the scaling parameter. The scaling relationship derived from the analytical model is then compared to established power-to-failure ESD models. The impact of MOSFET scaling on the ESD robustness of MOSFET structures is then discussed. MOSFET scaling as a function of technology generation shows that snapback breakover and sustaining voltages are decreasing with each technology generation. Optimization, design constraints and technology tradeoffs in CMOS technology development are then shown using a design curve methodology.

The effects of family cohesiveness and peer encouragement on the development of adolescent alcohol use: a cohort-sequential approach to the analysis of longitudinal data.

This article demonstrates a latent growth curve methodology for analyzing longitudinal data for adolescent alcohol use by combining information from different overlapping age cohorts to form a single developmental trajectory. Hypotheses concerning the form of growth in alcohol use, the extent of individual differences in the common trajectory over time, and covariates influencing both initial status and the form of growth were tested. Utilizing five separate age cohorts each measured over the same 4-year period, results suggested a common trajectory existed across the 8 years represented by the cohort-sequential analysis, with alcohol use increasing more rapidly during the adolescents' transition to high school. Family cohesion and peer encouragement for alcohol use were hypothesized to influence both initial status and the trajectory of alcohol consumption during adolescence. While family cohesion served to suppress initial levels of consumption delaying the upward trajectory of alcohol use, peer encouragement was related not only to initial, and elevated, levels of use, but was predictive of those changes that occurred during adolescence. Discussion involves the importance of family and peer influences in the development of adolescent alcohol use and the utility of the cohort-sequential approach in the analysis of longitudinal data.

Cut-off points for aggreate herd testing in the presence of disease clustering and correlation of test errors

In order to test if disease is present in a large herd, an investigator will often subject only a small sample of animals to a fallible diagnostic test. The herd is declared positive for disease if the number of test-positive animals is greater than or equal to a previously chosen cut-off value. Such a test, called an aggregate test, has a sensitivity and specificity that depends on the sample size, the cut-off point and the sensitivity and specificity of the individual test. It also depends on the distribution of the disease among the herds being tested and on the fact that factors such as herd-level seropositivity may cause some herds to be more prone to testing errors than others. In this paper, we use the beta-binomial distribution to model all these factors and thereby calculate and tabulate aggregate test sensitivities and specificities under a variety of conditions. Receiver operating characteristic (ROC) curve methodology permits the choice of optimum sample sizes and cut-off values. We also investigate the situation in which an investigator may be willing to miss detecting the disease if the prevalence in the herd is low. A compiled FORTRAN program for the calculation of aggregate test cut-off point properties, including positive and negative predictive values, is available from the authors.

Effect of number of conditioning trials on the development of associative tolerance to morphine.

The acquisition of associative tolerance to the analgesic effects of morphine was investigated by giving independent groups of rats 1, 3, 5, 8, 14, 20, or 30 administrations of drug either explicitly paired or unpaired with a distinctive context. Tolerance, assessed on a tail-flick device using dose-response curve (DRC) methodology, developed more rapidly and reached greater magnitude when morphine and the distinctive context were explicitly paired rather than explicitly unpaired. Tolerance magnitude in both conditions reached a maximum at eight conditioning sessions. It is argued that the tolerance found in both treatment groups was associatively controlled. The function of handling and injection cues as conditioned stimuli, and the deleterious effects of latent inhibition and partial reinforcement on conditioned excitation and conditioned inhibition are discussed.

The use of X-ray diffraction rocking curve methodology for assessment of the c-axis orientation in BiSrCaCuO superconducting thin films

An X-ray diffraction theta scan rocking curve analysis method has been developed which allows one to assess the relative degree of c-axis preferred orientation of BiSrCaCuO superconducting ceramic thin films deposited on (100) MgO and Ag foil substrates. The full width at half maximum (FWHM) of the rocking curve peak is taken as a relative measure of c-axis orientation. Precision measurements of the data collection parameters, sample holder mounting, and instrument loading of the sample were performed. Defocusing of the X-ray beam was characterized using random α-Al2O3 powder and a (100) Si wafer. Rocking curves of the BiSrCaCuO 37 Å-110 K superconducting phase (0014) peak for a random powder, thin film on Ag substrate, and thin film on (100) MgO were obtained with FWHM values of > 20° ∼ 5° and ∼0.3°θ, respectively.

Receiver operator characteristic (ROC) curves and non‐normal data: An empirical study

This paper evaluates the performance of several diagnostic kits for assessing levels of serum prostatic acid phosphatase on patients at different stages of cancer of the prostate. Each patient was studied with several kits. We compare results obtained for receiver operator characteristic (ROC) curve methodology with data assumed to follow a normal distribution, with log-transformed data assumed to follow a normal distribution, and when neither of these assumptions holds. There were important differences between the results of the different approaches. For these data, the normal distribution assumption should be used with extreme caution. The log-transformed based results compared favourably with the non-parametric, but unconsidered application of the method should be avoided.

In-vitro activity of SCH39304 in comparison with amphotericin B and flaconazole

The in-vitro activity of SCH39304, a new imidazole, was compared with that of amphotericin B using two media (Sabouraud dextrose and tissue culture (TC) medium) with or without 25% human serum. At an inoculum of 1.5 X 10(4) cfu/ml, the IC95% for amphotericin B ranged from 0.08 to 0.3 mg/l irrespective of the medium. At the same inoculum, the IC95% of the two imidazoles ranged from 0.3 to greater than 80 mg/l. The inoculum effect (from 1.5 X 10(4) to 1.5 X 10(5) cfu/ml) was less than 1 dilution for the three antifungal agents. Serum increased the inhibitory activity (IC80%) of SCH39304 and fluconazole but not of amphotericin B. The IC80%, IC95% and minimal fungicidal concentration (MFC) for amphotericin B usually ranged within two dilutions. Using kill curve methodology, the initial killing rate (0-4 h) of amphotericin B correlated with concentration (P less than 0.001), and was faster in TC medium than in Sabouraud dextrose (P less than 0.0006). SCH39304 and fluconazole did not produce any significant killing over the range of concentrations tested (0.5-20 mg/l). SCH39304 was similar to fluconazole.