Nonparametric location estimators in the randomized complete block design

Several tests for the comparison of different groups in the randomized complete block design exist. However, there is a lack of robust estimators for the location difference between one group and all the others on the original scale. The relative marginal effects are commonly used in this situation, but they are more difficult to interpret and use by less experienced people because of the different scale. In this paper two nonparametric estimators for the comparison of one group against the others in the randomized complete block design will be presented. Theoretical results such as asymptotic normality, consistency, translation invariance, scale preservation, unbiasedness, and median unbiasedness are derived. The finite sample behavior of these estimators is derived by simulations of different scenarios. In addition, possible confidence intervals with these estimators are discussed and their behavior derived also by simulations.

Hadronic light-by-light scattering and the muon g−2

The largest uncertainties in the Standard Model calculation of the anomalous magnetic moment of the muon (g − 2)μ come from hadronic contributions. In particular, it can be expected that in a few years the subleading hadronic light-by-light (HLbL) contribution will dominate the theory uncertainty. We present a dispersive description of the HLbL tensor, which is based on unitarity, analyticity, crossing symmetry, and gauge invariance. Such a model-independent Approach opens up an avenue towards a data-driven determination of the HLbL contribution to the (g − 2)μ.

Finite volume effects in chiral perturbation theory with twisted boundary conditions

We study the effects of a finite cubic volume with twisted boundary conditions on pseudoscalar mesons. We apply Chiral Perturbation Theory in the p-regime and introduce the twist by means of a constant vector field. The corrections of masses, decay constants, pseudoscalar coupling constants and form factors are calculated at next-to-leading order. We detail the derivations and compare with results available in the literature. In some case there is disagreement due to a different treatment of new extra terms generated from the breaking of the cubic invariance. We advocate to treat such terms as renormalization terms of the twisting angles and reabsorb them in the on-shell conditions. We confirm that the corrections of masses, decay constants, pseudoscalar coupling constants are related by means of chiral Ward identities. Furthermore, we show that the matrix elements of the scalar (resp. vector) form factor satisfies the Feynman–Hellman Theorem (resp. the Ward–Takahashi identity). To show the Ward–Takahashi identity we construct an effective field theory for charged pions which is invariant under electromagnetic gauge transformations and which reproduces the results obtained with Chiral Perturbation Theory at a vanishing momentum transfer. This generalizes considerations previously published for periodic boundary conditions to twisted boundary conditions. Another method to estimate the corrections in finite volume are asymptotic formulae. Asymptotic formulae were introduced by Lüscher and relate the corrections of a given physical quantity to an integral of a specific amplitude, evaluated in infinite volume. Here, we revise the original derivation of Lüscher and generalize it to finite volume with twisted boundary conditions. In some cases, the derivation involves complications due to extra terms generated from the breaking of the cubic invariance. We isolate such terms and treat them as renormalization terms just as done before. In that way, we derive asymptotic formulae for masses, decay constants, pseudoscalar coupling constants and scalar form factors. At the same time, we derive also asymptotic formulae for renormalization terms. We apply all these formulae in combination with Chiral Perturbation Theory and estimate the corrections beyond next-to-leading order. We show that asymptotic formulae for masses, decay constants, pseudoscalar coupling constants are related by means of chiral Ward identities. A similar relation connects in an independent way asymptotic formulae for renormalization terms. We check these relations for charged pions through a direct calculation. To conclude, a numerical analysis quantifies the importance of finite volume corrections at next-to-leading order and beyond. We perform a generic Analysis and illustrate two possible applications to real simulations.

Cross-cultural equivalence and associations among food insecurity and parental influences of children's fruit and vegetable consumption

Over the past several decades, the prevalence of obesity has dramatically increased. Cause for concern has increased because overweight and obesity are major contributors to morbidity and mortality. Intervention research aimed at reducing the prevalence of obesity has identified the family, specifically the parent, as a key component of the home environment. However, findings from dietary behavior change interventions have been disheartening because few studies have reported meaningful change, suggesting methodological and/or measurement issues within the intervention process. A lack of appropriate mediators and cross-cultural equivalence may partially explain the reason for little change.^ The study aims were to (1) evaluate the psychometric properties and assess the cross cultural equivalence of the Food Insecurity Scale (paper 1) and the modified Parent Feeding Practices Questionnaire (paper 2) and to assess the overall relationships among food insecurity, parent mediators, and parent behaviors towards children's dietary behavior (paper 3) through structural equation modeling and tests of invariance. The study aims were accomplished through conducting secondary analyses using baseline data from English- and Spanish-speaking Hispanic women who participated in the Healthy Families: Step by Step (BHF) study.^ Results indicated that although the FIS and the mPFPQ exhibited sound psychometric properties, the instruments exhibited a lack of invariance across language spoken groups. The lack of invariance was more pronounced in the FIS. Results also supported the theoretical framework identifying parent's perceived barriers and self-efficacy as mediators of parent's behaviors toward improving children's health eating. Results did not suggest that the relationships were moderated by food insecurity.^ In conclusion, the identification of differential item functioning in food insecurity and parent feeding practices may be beneficial in enhancing tailored interventions through the incorporation of cultural differences into the change mechanisms. However, future research needs to be conducted to determine if the lack of invariance demonstrates the existence of item bias or if it is a reflection of true difference among the language spoken groups. Additionally, obesity intervention studies targeting parent/family barriers and parent self-efficacy to provide/encourage healthy diets may result in an increase in parent behaviors which promote healthy eating behaviors among children. Future research should also examine a more complete causal pathway to determine whether parental changes in the mediators ultimately lead to an increase in healthy dietary behavior among children.^

The application of latent variable models to the assessment of determinants of HIV risk behavior

Studies on the relationship between psychosocial determinants and HIV risk behaviors have produced little evidence to support hypotheses based on theoretical relationships. One limitation inherent in many articles in the literature is the method of measurement of the determinants and the analytic approach selected. ^ To reduce the misclassification associated with unit scaling of measures specific to internalized homonegativity, I evaluated the psychometric properties of the Reactions to Homosexuality scale in a confirmatory factor analytic framework. In addition, I assessed the measurement invariance of the scale across racial/ethnic classifications in a sample of men who have sex with men. The resulting measure contained eight items loading on three first-order factors. Invariance assessment identified metric and partial strong invariance between racial/ethnic groups in the sample. ^ Application of the updated measure to a structural model allowed for the exploration of direct and indirect effects of internalized homonegativity on unprotected anal intercourse. Pathways identified in the model show that drug and alcohol use at last sexual encounter, the number of sexual partners in the previous three months and sexual compulsivity all contribute directly to risk behavior. Internalized homonegativity reduced the likelihood of exposure to drugs, alcohol or higher numbers of partners. For men who developed compulsive sexual behavior as a coping strategy for internalized homonegativity, there was an increase in the prevalence odds of risk behavior. ^ In the final stage of the analysis, I conducted a latent profile analysis of the items in the updated Reactions to Homosexuality scale. This analysis identified five distinct profiles, which suggested that the construct was not homogeneous in samples of men who have sex with men. Lack of prior consideration of these distinct manifestations of internalized homonegativity may have contributed to the analytic difficulty in identifying a relationship between the trait and high-risk sexual practices. ^

Affect and cognition measures in preference-based decisions: Validity testing of the Ottawa Decisional Conflict Scale and a decision-specific anxiety measure with men eligible for prostate cancer screening

Background. At present, prostate cancer screening (PCS) guidelines require a discussion of risks, benefits, alternatives, and personal values, making decision aids an important tool to help convey information and to help clarify values. Objective: The overall goal of this study is to provide evidence of the reliability and validity of a PCS anxiety measure and the Decisional Conflict Scale (DCS). Methods. Using data from a randomized, controlled PCS decision aid trial that measured PCS anxiety at baseline and DCS at baseline (T0) and at two-weeks (T2), four psychometric properties were assessed: (1) internal consistency reliability, indicated by factor analysis intraclass correlations and Cronbach's α; (2) construct validity, indicated by patterns of Pearson correlations among subscales; (3) discriminant validity, indicated by the measure's ability to discriminate between undecided men and those with a definite screening intention; and (4) factor validity and invariance using confirmatory factor analyses (CFA). Results. The PCS anxiety measure had adequate internal consistency reliability and good construct and discriminant validity. CFAs indicated that the 3-factor model did not have adequate fit. CFAs for a general PCS anxiety measure and a PSA anxiety measure indicated adequate fit. The general PCS anxiety measure was invariant across clinics. The DCS had adequate internal consistency reliability except for the support subscale and had adequate discriminate validity. Good construct validity was found at the private clinic, but was only found for the feeling informed subscale at the public clinic. The traditional DCS did not have adequate fit at T0 or at T2. The alternative DCS had adequate fit at T0 but was not identified at T2. Factor loadings indicated that two subscales, feeling informed and feeling clear about values, were not distinct factors. Conclusions. Our general PCS anxiety measure can be used in PCS decision aid studies. The alternative DCS may be appropriate for men eligible for PCS. Implications: More emphasis needs to be placed on the development of PCS anxiety items relating to testing procedures. We recommend that the two DCS versions be validated in other samples of men eligible for PCS and in other health care decisions that involve uncertainty. ^

Investigating the structure and form of condom decisional balance in an alternative school sample using confirmatory factor analysis

Teen pregnancy is a continuing problem, bringing with it a host of associated health and social risks. Alternative school students are especially at risk, but are historically under-represented in research. This is especially problematic in that instruments are needed to guide effective intervention development, but psychometrics for these instruments cannot be assumed when used in new populations. Decisional balance from the transtheoretical model offers a framework for understanding condom decision making, but has not been tested with alternative school students. Using responses from 640 subjects from Safer Choices 2 (a school-based HIV/STD/pregnancy prevention program implemented in 10 urban, southwestern alternative schools), a decisional balance scale for condom use was examined. A two-factor, mildly correlated model fit the data well. Tests of invariance examined scale functioning within gender and racial/ethnic groups. The underlying structure varied slightly based on subgroup, but on a practical level the impact on the use of scales was minimal. The structure and loadings were invariant across experimental condition. The pro scale was associated with a lower probability of having engaged in unprotected sexual behavior for sexually active subjects, and this association remained significant while controlling for demographic variables. The con scale did not show a significant association with engagement in unprotected sexual behaviors. Limitations and directions for future research were also discussed.^

Parental influence on adolescent smoking initiation among Mexican origin youth

Smoking is often initiated in adolescence through trying or experimenting with cigarettes. Smoking initiation is the beginning critical stage in the smoking trajectory often resulting in addiction. This dissertation examined the effect of parenting variables on smoking initiation behavior among 11–14 year old Mexican origin adolescents, a largely understudied group. The participants in this study were part of a population-based cohort of Mexican origin adolescents residing in Houston, Texas. ^ Aim 1 of this study assessed the appropriateness of the Family Life Questionnaire (FLQ) among Mexican origin adolescents. Second order confirmatory factor analysis (CFA) was performed to examine the factor structure of the FLQ and measurement invariance testing was conducted to evaluate the cross-cultural validity of this scale. Aim 2 analyzed cross-sectional associations between parenting variables and adolescent ever tried smoking behavior while aim 3 focused on prospective examination of changes in parenting variables from baseline to final follow-up on ever tried smoking behavior among never smokers. ^ Overall, the results of the CFA indicated that the original factor structure of the FLQ, with alterations, was a good fit for the Mexican origin adolescents. The measurement invariance analysis of the modified FLQ scale indicated adequate measurement invariance. The aim 2 cross-sectional analyses indicated that family cohesion was significantly associated with lower odds of ever tried smoking. Authoritarian parenting was significantly associated with smoking initiation only at the baseline while family conflict was significantly associated with smoking initiation only at the two-year final home visit. The findings from the aim 3 prospective analysis indicated that changes in levels of family cohesion and conflict are important predictors of smoking initiation among those who have never tried smoking. Specifically, perceiving low levels of family cohesion and a decrease in the family cohesion over two years, as well as perceiving high levels of family conflict and an increase in conflict over two years was associated with smoking initiation among never smokers. ^ In general, the findings of this study provide important insights on the links between parenting and adolescent smoking and assist in designing prevention and intervention programs that emphasize the role of family bonding to prevent adolescent smoking behavior. Family education programs for Mexican culture could also highlight the positive effects of authoritarian practices and good family communication to prevent family conflict and subsequent smoking behavior.^

Medida de concentración de Gini : Observaciones sobre las fórmulas de cálculo y el Principio de Población de Dalton. Propuesta de un factor de corrección

En la primera parte del presente trabajo se investigan diferentes formas de cálculo de la razón de concentración conocida como Coeficiente o Índice de Gini, y el no cumplimiento del axioma conocido como de "invariancia a la replicación" o "Principio de Población de Dalton" en algunas de ellas. El alcance de las conclusiones se limita al comportamiento de las fórmulas sometidas a prueba (se encuentran entre las más conocidas) cuando son aplicadas a distribuciones de datos desagregados. En la segunda parte se propone un factor de corrección para las fórmulas de cálculo analizadas, de manera que satisfagan el Principio de Población.

Medida de concentración de Gini : Observaciones sobre las fórmulas de cálculo y el Principio de Población de Dalton. Propuesta de un factor de corrección

En la primera parte del presente trabajo se investigan diferentes formas de cálculo de la razón de concentración conocida como Coeficiente o Índice de Gini, y el no cumplimiento del axioma conocido como de "invariancia a la replicación" o "Principio de Población de Dalton" en algunas de ellas. El alcance de las conclusiones se limita al comportamiento de las fórmulas sometidas a prueba (se encuentran entre las más conocidas) cuando son aplicadas a distribuciones de datos desagregados. En la segunda parte se propone un factor de corrección para las fórmulas de cálculo analizadas, de manera que satisfagan el Principio de Población.

Medida de concentración de Gini : Observaciones sobre las fórmulas de cálculo y el Principio de Población de Dalton. Propuesta de un factor de corrección

En la primera parte del presente trabajo se investigan diferentes formas de cálculo de la razón de concentración conocida como Coeficiente o Índice de Gini, y el no cumplimiento del axioma conocido como de "invariancia a la replicación" o "Principio de Población de Dalton" en algunas de ellas. El alcance de las conclusiones se limita al comportamiento de las fórmulas sometidas a prueba (se encuentran entre las más conocidas) cuando son aplicadas a distribuciones de datos desagregados. En la segunda parte se propone un factor de corrección para las fórmulas de cálculo analizadas, de manera que satisfagan el Principio de Población.

Medida de concentración de Gini : Observaciones sobre las fórmulas de cálculo y el Principio de Población de Dalton. Propuesta de un factor de corrección

En la primera parte del presente trabajo se investigan diferentes formas de cálculo de la razón de concentración conocida como Coeficiente o Índice de Gini, y el no cumplimiento del axioma conocido como de "invariancia a la replicación" o "Principio de Población de Dalton" en algunas de ellas. El alcance de las conclusiones se limita al comportamiento de las fórmulas sometidas a prueba (se encuentran entre las más conocidas) cuando son aplicadas a distribuciones de datos desagregados. En la segunda parte se propone un factor de corrección para las fórmulas de cálculo analizadas, de manera que satisfagan el Principio de Población.

A non-perturbative renormalization group study of the stochastic NavierStokes equation

We study the renormalization group flow of the average action of the stochastic Navier-Stokes equation with power-law forcing. Using Galilean invariance, we introduce a nonperturbative approximation adapted to the zero-frequency sector of the theory in the parametric range of the Hölder exponent 4−2 ɛ of the forcing where real-space local interactions are relevant. In any spatial dimension d, we observe the convergence of the resulting renormalization group flow to a unique fixed point which yields a kinetic energy spectrum scaling in agreement with canonical dimension analysis. Kolmogorov's −5/3 law is, thus, recovered for ɛ=2 as also predicted by perturbative renormalization. At variance with the perturbative prediction, the −5/3 law emerges in the presence of a saturation in the ɛ dependence of the scaling dimension of the eddy diffusivity at ɛ=3/2 when, according to perturbative renormalization, the velocity field becomes infrared relevant.

Deep levels in a-plane, high Mg-content MgxZn1-xO epitaxial layers grown by molecular beam epitaxy

Deep level defects in n-type unintentionally doped a-plane MgxZn1−xO, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of MgxZn1−xO were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of Ec − 1.4 eV, 2.1 eV, 2.6 V, and Ev + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three states were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at Ec − 2.1 eV, Ev + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at Ev + 0.3 eV and Ec − 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the Ev + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the Ec − 1.4 eV and Ec − 2.6 eV levels in Mg alloyed samples.

Bandlimited Airy Pulses for Invariant Propagation in Single-Mode Fibers

By spectral analysis, and using joint time-frequency representations, we present the theoretical basis to design invariant bandlimited Airy pulses with an arbitrary degree of robustness and an arbitrary range of single-mode fiber chromatic dispersion. The numerically simulated examples confirm the theoretically predicted pulse partial invariance in the propagation of the pulse in the fiber.