A new package for fitting random effect models

Random effects have become a standard concept in statistical modelling over the last decades. They enter a wide range of applications by providing a simple tool to account for such problems as model misspecification, unobserved (latent) variables, unobserved heterogeneity, and the like. One of the most important model classes for the use of random effects is the generalized linear model. Aitkin (1999) noted that “the literature on random effects in generalized linear models is now extensive”, and this is certainly even more true today

lcc: an R package to estimate the concordance correlation, Pearson correlation and accuracy over time

Background and Objective: Observational studies and experiments in medicine, pharmacology and agronomy are often concerned with assessing whether different methods/raters produce similar values over the time when measuring a quantitative variable. This article aims to describe the statistical package lcc, for are, that can be used to estimate the extent of agreement between two (or more) methods over the time, and illustrate the developed methodology using three real examples. Methods: The longitudinal concordance correlation, longitudinal Pearson correlation, and longitudinal accuracy functions can be estimated based on fixed effects and variance components of the mixed-effects regression model. Inference is made through bootstrap confidence intervals and diagnostic can be done via plots, and statistical tests. Results: The main features of the package are estimation and inference about the extent of agreement using numerical and graphical summaries. Moreover, our approach accommodates both balanced and unbalanced experimental designs or observational studies, and allows for different within-group error structures, while allowing for the inclusion of covariates in the linear predictor to control systematic variations in the response. All examples show that our methodology is flexible and can be applied to many different data types. Conclusions: The lcc package, available on the CRAN repository, proved to be a useful tool to describe the agreement between two or more methods over time, allowing the detection of changes in the extent of agreement. The inclusion of different structures for the variance-covariance matrices of random effects and residuals makes the package flexible for working with different types of databases

Angular anisotropy of the fusion-fission and quasifission fragments

The anisotropy in the angular distribution of the fusion-fission and quasifission fragments for the $^{16}$O+$^{238}$U, $^{19}$F+$^{208}$Pb and $^{32}$S+$^{208}$Pb reactions is studied by analyzing the angular momentum distributions of the dinuclear system and compound nucleus which are formed after capture and complete fusion, respectively. The orientation angles of axial symmetry axes of colliding nuclei to the beam direction are taken into account for the calculation of the variance of the projection of the total spin onto the fission axis. It is shown that the deviation of the experimental angular anisotropy from the statistical model picture is connected with the contribution of the quasifission fragments which is dominant in the $^{32}$S+$^{208}$Pb reaction. Enhancement of anisotropy at low energies in the $^{16}$O+$^{238}$U reaction is connected with quasifission of the dinuclear system having low temperature and effective moment of inertia.Comment: 17 pages 8 figures. Submitted to Euro. Phys. Jour.

Influence of glyphosate on rhizosphere microorganisms and their ability to solubilise phosphate

Objective: To determine cowpea rhizosphere microor-ganisms with phosphate solubilizing potential in a soil treated with glyphosate. Methods: Four different con-centrations of glyphosate herbicides (0.00, 0.50, 1.00, and 3.00) were assayed. Cowpea seedlings were planted and later harvested after 30 days of germina-tion. Microorganisms from rhizosphere treated with glyphosate were cultured and identified using selective media Wakesman A and B agar. The activity of isolates were evaluated by Tricalcium phosphate solubilization and screening for phosphatase in a Pikovskaya me-dium.. Results: Bacillus cereus, Bacillus subtilis, Micrococ-cus luteus, Pseudomonas aeruginosa, Proteus mirabi-lis, Bacillus pumilis, Staphylococcus aureus, Aspergil-lus flavus, Rhizopus nigrifican, and Aspergillus sapro-phyiticus were obtained from the glyphosate treated soil. There was decrease in the bacterial and fungal population in the rhizosphere as glyphosate concentra-tion increased. The concentration of the solubilized Tricalcium phosphate ranged from 42.48 to 515.78gl-1. Micrococcus luteus, Bacillus subtilis, Proteus mirabi-lis, Aspergillus flavus, Aspergillus saprophyticus iso-lated at the different concentrations of glyphosate have increased phosphate solubilization with reduction in their pH. Proteus mirabilis showed the highest phos-phatase activity (23.157mM/min/ml) at 30hrs and As-pergillus saprophyticus showed highest phosphatase activity (35.263 mM/min/ml) at 72hrs. Bacillus sub-tilis had the lowest protein concentration (3.034mg/ml) at 12hrs. Conclusion: This study showed that these rhizosphere microorganisms when applied as inoculants into the soil at different concentration of glyphosate can help increase the availability of soluble phosphates