Multidimensional structure and measurement invariance of school engagement.

This study examined the multidimensional structure and measurement invariance of a school engagement instrument using confirmatory factor analysis (CFA), exploratory structural equation modeling (ESEM), bifactor CFA (BCFA), and bifactor ESEM (BESEM). Participants consisted of 1731 students in Grades 9 - 11 from the 4-H Study of Positive Youth Development in the United States. The use of the CFA, ESEM, BCFA, and BESEM models was expected to provide more insight into the cross-loading and hierarchical structures of school engagement. We found empirical evidence to support the (a) tripartite factor structure of school engagement, (b) existence of cross-loadings and hierarchical structures, (c) measurement invariance across gender (male vs female) and race (European American vs African American), and (d) expected latent means differences by gender.

Parents' gesture adaptations to children with autism spectrum disorder.

The present study focused on parents' social cue use in relation to young children's attention. Participants were ten parent-child dyads; all children were 36 to 60 months old and were either typically developing (TD) or were diagnosed with autism spectrum disorder (ASD). Children wore a head-mounted camera that recorded the proximate child view while their parent played with them. The study compared the following between the TD and ASD groups: (a) frequency of parent's gesture use; (b) parents' monitoring of their child's face; and (c) how children looked at parents' gestures. Results from Bayesian estimation indicated that, compared to the TD group, parents of children with ASD produced more gestures, more closely monitored their children's faces, and provided more scaffolding for their children's visual experiences. Our findings suggest the importance of further investigating parents' visual and gestural scaffolding as a potential developmental mechanism for children's early learning, including for children with ASD.

Detecting Differential Item Functioning Using the Logistic Regression Procedure in Small Samples.

The logistic regression (LR) procedure for testing differential item functioning (DIF) typically depends on the asymptotic sampling distributions. The likelihood ratio test (LRT) usually relies on the asymptotic chi-square distribution. Also, the Wald test is typically based on the asymptotic normality of the maximum likelihood (ML) estimation, and the Wald statistic is tested using the asymptotic chi-square distribution. However, in small samples, the asymptotic assumptions may not work well. The penalized maximum likelihood (PML) estimation removes the first-order finite sample bias from the ML estimation, and the bootstrap method constructs the empirical sampling distribution. This study compares the performances of the LR procedures based on the LRT, Wald test, penalized likelihood ratio test (PLRT), and bootstrap likelihood ratio test (BLRT) in terms of the statistical power and type I error for testing uniform and non-uniform DIF. The result of the simulation study shows that the LRT with the asymptotic chi-square distribution works well even in small samples.

Neighborhood × Serotonin Transporter Linked Polymorphic Region (5-HTTLPR) interactions for substance use from ages 10 to 24 years using a harmonized data set of African American children.

This study investigated the influences of neighborhood factors (residential stability and neighborhood disadvantage) and variants of the serotonin transporter linked polymorphic region (5-HTTLPR) genotype on the development of substance use among African American children aged 10-24 years. To accomplish this, a harmonized data set of five longitudinal studies was created via pooling overlapping age cohorts to establish a database with 2,689 children and 12,474 data points to span ages 10-24 years. A description of steps used in the development of the harmonized data set is provided, including how issues such as the measurement equivalence of constructs were addressed. A sequence of multilevel models was specified to evaluate Gene × Environment effects on growth of substance use across time. Findings indicated that residential instability was associated with higher levels and a steeper gradient of growth in substance use across time. The inclusion of the 5-HTTLPR genotype provided greater precision to the relationships in that higher residential instability, in conjunction with the risk variant of 5-HTTLPR (i.e., the short allele), was associated with the highest level and steepest gradient of growth in substance use across ages 10-24 years. The findings demonstrated how the creation of a harmonized data set increased statistical power to test Gene × Environment interactions for an under studied sample.

Constructing Confidence Intervals for Effect Size Measures of an Indirect Effect.

Confidence intervals for an effect size can provide the information about the magnitude of an effect and its precision as well as the binary decision about the existence of an effect. In this study, the performances of five different methods for constructing confidence intervals for ratio effect size measures of an indirect effect were compared in terms of power, coverage rates, Type I error rates, and widths of confidence intervals. The five methods include the percentile bootstrap method, the bias-corrected and accelerated (BCa) bootstrap method, the delta method, the Fieller method, and the Monte Carlo method. The results were discussed with respect to the adequacy of the distributional assumptions and the nature of ratio quantity. The confidence intervals from the five methods showed similar results for samples of more than 500, whereas, for samples of less than 500, the confidence intervals were sufficiently narrow to convey the information about the population effect sizes only when the effect sizes of regression coefficients defining the indirect effect are large.

Confidence intervals for distinguishing ordinal and disordinal interactions in multiple regression.

Distinguishing between ordinal and disordinal interaction in multiple regression is useful in testing many interesting theoretical hypotheses. Because the distinction is made based on the location of a crossover point of 2 simple regression lines, confidence intervals of the crossover point can be used to distinguish ordinal and disordinal interactions. This study examined 2 factors that need to be considered in constructing confidence intervals of the crossover point: (a) the assumption about the sampling distribution of the crossover point, and (b) the possibility of abnormally wide confidence intervals for the crossover point. A Monte Carlo simulation study was conducted to compare 6 different methods for constructing confidence intervals of the crossover point in terms of the coverage rate, the proportion of true values that fall to the left or right of the confidence intervals, and the average width of the confidence intervals. The methods include the reparameterization, delta, Fieller, basic bootstrap, percentile bootstrap, and bias-corrected accelerated bootstrap methods. The results of our Monte Carlo simulation study suggest that statistical inference using confidence intervals to distinguish ordinal and disordinal interaction requires sample sizes more than 500 to be able to provide sufficiently narrow confidence intervals to identify the location of the crossover point.

Dopamine receptor gene d4 polymorphisms and early sexual onset: gender and environmental moderation in a sample of african-american youth.

PURPOSE: Early sexual onset and its consequences disproportionately affect African-American youth, particularly male youth. The dopamine receptor D4 gene (DRD4) has been linked to sexual activity and other forms of appetitive behavior, particularly for male youth and in combination with environmental factors (gene × environment [G × E] effects). The differential susceptibility perspective suggests that DRD4 may exert this effect by amplifying the effects of both positive and negative environments. We hypothesized that DRD4 status would amplify the influence of both positive and negative neighborhood environments on early sexual onset among male, but not female, African-Americans. METHODS: Hypotheses were tested with self-report, biospecimen, and census data from five prospective studies of male and female African-American youth in rural Georgia communities, N = 1,677. Early sexual onset was defined as intercourse before age 14. RESULTS: No significant G × E findings emerged for female youth. Male youth with a DRD4 long allele were more likely than those with two DRD4 short alleles to report early sexual onset in negative community environments and not to report early onset in positive community environments. CONCLUSIONS: Dopaminergic regulation of adolescent sexual behaviors may operate differently by gender. DRD4 operated as an environmental amplification rather than a vulnerability factor.

Carbon-deposited TiO2 3D inverse opal photocatalysts: visible-light photocatalytic activity and enhanced activity in a viscous solution.

We for the first time demonstrated carbon-deposited TiO2 inverse opal (C-TiO2 IO) structures as highly efficient visible photocatalysts. The carbon deposition proceeded via high-temperature pyrolysis of phloroglucinol/formaldehyde resol, which had been coated onto the TiO2 IO structures. Carbon deposition formed a carbon layer and doped the TiO2 interface, which synergistically enhanced visible-light absorption. We directly measured the visible-light photocatalytic activity by constructing solar cells comprising the C-TiO2 IO electrode. Photocatalytic degradation of organic dyes in a solution was also evaluated. Photocatalytic dye degradation under visible light was only observed in the presence of the C-TiO2 IO sample and was increased with the content of carbon deposition. The IO structures could be readily decorated with TiO2 nanoparticles to increase the surface area and enhance the photocatalytic activity. Notably, the photocatalytic reaction was found to proceed in a viscous polymeric solution. A comparison of the mesoporous TiO2 structure and the IO TiO2 structure revealed that the latter performed better as the solution viscosity increased. This result was attributed to facile diffusion into the fully connected and low-tortuosity macropore network of the IO structure.

Fractal analysis of mandibular trabecular bone: optimal tile sizes for the tile counting method.

PURPOSE: This study was performed to determine the optimal tile size for the fractal dimension of the mandibular trabecular bone using a tile counting method. MATERIALS AND METHODS: Digital intraoral radiographic images were obtained at the mandibular angle, molar, premolar, and incisor regions of 29 human dry mandibles. After preprocessing, the parameters representing morphometric characteristics of the trabecular bone were calculated. The fractal dimensions of the processed images were analyzed in various tile sizes by the tile counting method. RESULTS: The optimal range of tile size was 0.132 mm to 0.396 mm for the fractal dimension using the tile counting method. The sizes were closely related to the morphometric parameters. CONCLUSION: The fractal dimension of mandibular trabecular bone, as calculated with the tile counting method, can be best characterized with a range of tile sizes from 0.132 to 0.396 mm.

Positive contrast technique for the detection and quantification of superparamagnetic iron oxide nanoparticles in MRI.

In vivo detection and quantification of cells labeled with superparamagnetic iron oxide (SPIO) nanoparticles has been attracting increasing attention. In particular, positive contrast methods, such as susceptibility gradient mapping (SGM) and phase gradient mapping (PGM), have been proposed for the improved detection of SPIO nanoparticles. In this study, a different implementation of the PGM method is introduced; it calculates the phase gradient in the image space using a fast Fourier transform without the need for phase unwrapping. We first compared positive contrast generation between the PGM and SGM methods, which estimates the susceptibility gradient in k space through echo shift measurements. Next, PGM was applied to quantify SPIO concentrations by fitting the resulting phase gradient maps to those of a theoretical model. MR experiments were conducted using a 3-T magnet scanner to acquire two datasets: the first was acquired from a gelatin phantom with three SPIO-doped vials of different concentrations, and the second was obtained in vivo from a nude rat with SPIO-labeled C6 glioma cells implanted in the flanks. The sensitivity of the PGM and SGM methods was compared using various factors, including different SPIO concentrations, TEs and signal-to-noise ratios. Based on the theoretical model of an infinite cylinder, the results demonstrated that, without loss of spatial resolution, the PGM method presents positive contrast maps with a higher sensitivity than SGM at medium and low SPIO concentrations, whereas SGM is more sensitive than PGM at longer TEs. The quantification of SPIO concentrations using the phantom dataset was also reported. On the basis of the same infinite cylinder model, it was shown that the PGM method provides an accurate estimation of SPIO concentration.

Dynamic contrast-enhanced magnetic resonance imaging of canine brain tumors.

We evaluated dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in canine brain tumors. Magnetic resonance data sets were collected on seven canine intracranial tumors with a 3 T magnet using a T1-weighted fast spin echo fluid attenuated inversion recovery sequence after an IV bolus injection (0.2 mmol/kg) of Gd-DTPA. The tumors were confirmed histopathologically as adenocarcinoma (n=1), ependymoma (n=1), meningioma (n=3), oligodendroglioma (n=1), and pituitary macroadenoma (n=1) The data were analyzed using a two-compartment pharmacokinetic model for estimation of three enhancement parameters, E(R) (rate of enhancement), Kel (rate of elimination), and Kep (rate constant), and a model-free phenomenologic parameter initial area under the Gd concentration curve (IAUGC) defined over the first 90s postenhancement. Pearson's correlations were calculated between parameters of the two methods. The IAUGC has a relatively strong association with the rate of enhancement E(R), with r ranges from 0.4 to 0.9, but it was weakly associated with Kep and Kel. To determine whether any two tumors differed significantly, the Kohnlmogorov-Smirnov test was used. The results showed that there were statistical differences (P < 0.05) between distributions of the enhancement pattern of each tumor. These kinetic parameters may characterize the perfusion and vascular permeability of the tumors and the IAUGC may reflect blood flow, vascular permeability, and the fraction of interstitial space. The kinetic parameters and the IAUGC derived from DCE-MRI present complementary information and they may be appropriate to noninvasively differentiate canine brain tumors although a larger prospective study is necessary.

Automatic noise robust registration of radiographs for subtraction using strategic local correlation: an application to radiographs of dental implants.

Most of digital subtraction methods in dental radiography are based on registration using manual landmarks. We have developed an automatic registration method without using the manual selection of landmarks. By restricting a geometrical matching of images to a region of interest (ROI), we compare the cross-correlation coefficient only between the ROIs. The affine or perspective transform parameters satisfying maximum of cross-correlation between the local regions are searched iteratively by a fast searching strategy. The parameters are searched on the 14 scale image coarsely and then, the fine registration is performed on the original scale image. The developed method can match the images corrupted by Gaussian noise with the same accuracy for the images without any transform simulation. The registration accuracy of the perspective method shows a 17% improvement over the manual method. The application of the developed method to radiographs of dental implants provides an automatic noise robust registration with high accuracy in almost real time.

Nelumbinis Semen reverses a decrease in 5-HT1A receptor binding induced by chronic mild stress, a depression-like symptom.

Depression is associated with a dysfunctional serotonin (5-hydroxytryptamine; 5-HT) system. More recently, several lines of evidence suggest that an important factor in the development of depression may be a deficit in the function and expression of 5-HT1A receptors. The present study assessed if Nelumbinis Semen (N.s.) had an anti-depression effect through reversing a decrease in 5-HT1A receptor binding in rats with depression-like symptoms induced by chronic mild stress. Using a 5-HT1A receptor binding assay, with a specific 5-HT1A receptor agonist, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino) tetralin), the mechanism of the anti-depression effect of N.s. on rats was investigated, and the effects compared with two well-known antidepressants, Hyperium Perforatum (St. Johns Wort) and fluoxetine (Prozac). Animals were divided into five groups: the normal (N) group without chronic mild stress (CMS), the control (C) group under CMS for 8 weeks, the Nelumbinis Semen (N.s.) treatment group under CMS for 8 weeks, the Hyperium Perforatum (H.p.) treatment group under CMS for 8 weeks and finally, the fluoxetine (F) treatment group under CMS for 8 weeks. Each treatment was administered to rats during the last 4 weeks of the 8-week CMS. A sucrose intake test was performed to test the anti-depression effect of N.s. The N.s. treatment significantly reversed the decreased sucrose intake under CMS (P < 0.05 compared to control group under CMS). In the CA2 and CA3 regions of the hippocampus, both N.s. and H.p. reversed the CMS-induced decrease in 5-HT1A receptor binding. In the I to II regions of the frontal cortex, N.s. and H.p. also reversed the CMS-induced decrease in 5-HT1A receptor binding, and even showed a significant increase in 5-HT1A receptor binding compared to the F treatment group (N.s. vs. P, p < 0.05, H.p. vs. P, p < 0.05). However, in the hypothalamus, all treatments reversed the CMS-induced decrease in 5-HT1A receptor binding. This reversal effect of N.s. on the decrease in 5-HT1A receptor binding in the frontal cortex, hippocampus and hypothalamus of rat brains was very similar to that of H.p, but different from that of F. It is concluded that N.s. presents an anti-depression effect through enhancing 5-HT1A receptor binding.

Nelumbinis Semen reverses a decrease in 5-HT1A receptor binding induced by chronic mild stress, a depression-like symptom.

Depression is associated with a dysfunctional serotonin (5-hydroxytryptamine; 5-HT) system. More recently, several lines of evidence suggest that an important factor in the development of depression may be a deficit in the function and expression of 5-HT1A receptors. The present study assessed ifNelumbinis Semen (N. s.) had an anti-depression effect through reversing a decrease in 5-HT1A receptor binding in rats with depression-like symptoms induced by chronic mild stress. Using a 5-HT1A receptor binding assay, with a specific 5-HT1A receptor agonist, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino) tetralin), the mechanism of the anti-depression effect ofN. s. on rats was investigated, and the effects compared with two well-known anti-depressants,Hyperium Perforatum (St. Johns Wort) and fluoxetine (Prozac). Animals were divided into five groups: the normal (N) group without chronic mild stress (CMS), the control (C) group under CMS for 8 weeks, theNelumbinis Semen (N. s.) treatment group under CMS for 8 weeks, theHyperium Perforatum (H. p.) treatment group under CMS for 8 weeks and finally, the fluoxetine (F) treatment group under CMS for 8 weeks. Each treatment was administered to rats during the last 4 weeks of the 8-week CMS. A sucrose intake test was performed to test the anti-depression effect ofN. s. TheN. s. treatment significantly reversed the decreased sucrose intake under CMS (P<0.05 compared to control group under CMS). In the CA2 and CA3 regions of the hippocampus, bothN. s. andH. p. reversed the CMS-induced decrease in 5-HT1A receptor binding. In the I to II regions of the frontal cortex,N. s. andH. p. also reversed the CMS-induced decrease in 5-HT1A receptor binding, and even showed a significant increase in 5-HT1A receptor binding compared to the F treatment group (N. s. vs. P, p<0.05,H. p. vs. P, p<0.05). However, in the hypothalamus, all treatments reversed the CMS-induced decrease in 5-HT1A receptor binding. This reversal effect ofN. s. on the decrease in 5-HT1A receptor binding in the frontal cortex, hippocampus and hypothalamus of rat brains was very similar to that ofH. p, but different from that of F. It is concluded thatN. s. presents an anti-depression effect through enhancing 5-HT1A receptor binding.

Effect of different temperatures and penetration depths of a System B plugger in the filling of artificially created oval canals.

OBJECTIVES: The purpose of this study was to compare the gutta-percha-filled area in oval canals while varying the temperature and penetration depth of the System B plugger. STUDY DESIGN: Seventy-five resin blocks, with artificially created oval canals, were obturated by using a continuous wave technique. In groups 1, 2, and 3, the plugger was introduced to a depth of 4 mm from the apex at set temperatures of 100, 200, and 350 degrees C, respectively. In group 4, the plugger was inserted to a depth of 2 mm from the apex at a set temperature of 200 degrees C. Group 5 was obturated in the same way as group 2, and then an additional cold plugging was performed to a depth of 3 mm from the apex. The cross sections of the obturated canals were photographed, and the percentage of the gutta-percha-filled area (PGP) was measured. RESULTS: No significant differences were found between the 3 different temperature settings (P >.05). At 1 mm from the apex, group 4 showed the highest PGP (95.57% +/- 6.86), followed by group 5 (84.72% +/- 12.19), and group 2 (67.33 +/- 13.03) (P <.05). CONCLUSION: In artificially created oval canals, plugger temperature within the range used in this study did not affect the PGP. However, the penetration depth of the plugger was significantly related to PGP.