Search results for "Statistical"

Theoretical study of Fe doping and oxidation–reduction influence on the photorefractive effect in BaTiO_3

1993

We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+–Fe3+, Fe3+–Fe4+, VO••–VO•, and VO•-VOx. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation–reduction treatments, and measurement parameters.

Testing international dental maturation scoring system and population-specific Demirjian versions on Saudi sub-population

2013

Objectives: The purpose of this study was to test the applicability of the Demirjian method and revised versions for estimating chronological age (CA) from dental age (DA) in a sample of children. Study Design: A sample of 252 individuals of known age (4 to 14 yrs), sex (males: 125, females: 127), and ethnicity (Saudi) was collected. Each individual was aged using the original Demirjian method and revised versions, including Saudi, Kuwaiti, Belgian, and revised international curves. The differences between dental age and chronological age were analyzed using paired sample t-tests with Bonferroni corrections and multinomial regression tests at the 0.05 level of significance. Results: The res…

Prevalence of lip lesions in an Indian population

2014

Objectives: Lip lesions are a frequent cause of consultation in dentistry, as they comprise a signifi cant proportion of the oral lesions. The aim of the present study was to identify the different lip lesions and determine their prevalence in an Indian population. Material and methods: 5231 patients visiting a Department of Oral Medicine and Radiology were examined for the presence of different lip lesions during the period from October, 2011 to May, 2013. The statistical analysis was done using Chi-square test and p<0.05 was considered to be statistically signifi cant. Results: The age of the patients ranged from 8-70 years with a mean age of 32.6 years. The prevalence of lip lesions was …

FAST OSCILLATING MIGRATIONS IN A PREDATOR-PREY MODEL

1996

The aim of this paper is to give a method which permits us to describe how individual properties can emerge at the population level, in population dynamics. We consider interacting populations. In order to take into account the spatial or behavioral heterogeneity, we subdivide each population into subpopulations. A given subpopulation corresponds to those individuals having the same behavior and who are in a homogeneous environment. Furthermore, we assume that the migration process is faster than the growth and interaction processes. Therefore, we must study models with many variables coupled together into large scaled differential systems. Firstly, our method permits us to reduce these co…

Time evolution of non-lethal infectious diseases: a semi-continuous approach.

2005

A model describing the dynamics related to the spreading of non-lethal infectious diseases in a fixed-size population is proposed. The model consists of a non-linear delay-differential equation describing the time evolution of the increment in the number of infectious individuals and depends upon a limited number of parameters. Predictions are in good qualitative agreement with data on influenza.

Comparison of non-Markovianity criteria in a qubit system under random external fields

2013

We give the map representing the evolution of a qubit under the action of non-dissipative random external fields. From this map we construct the corresponding master equation that in turn allows us to phenomenologically introduce population damping of the qubit system. We then compare, in this system, the time-regions when non-Markovianity is present on the basis of different criteria both for the non-dissipative and dissipative case. We show that the adopted criteria agree both in the non-dissipative case and in the presence of population damping.

Establishing Equivalence or Non-Inferiority in Clinical Trials

2012

Background: An increasing number of clinical trials are being performed to show the absence of relevant differences between the effects of two treatments. The primary care physician makes use of the results of so-called equivalence studies, at least indirectly, practically every day. Equally important are active control clinical trials in which the efficacy of a new treatment has to be proven through demonstrating non-inferiority as compared to a standard treatment. Methods: Explanation of basic principles and statistical techniques with reference to the original literature; selective searches in the medical literature. Results: First of all, a suitable distributional parameter must be chos…

Dimensional Latent Structure of Relationship Quality: Results of Three Representative Population Samples

2015

One central issue for every latent construct in psychology (e.g., relationship quality) is its latent nature: Differences in intelligence, for example, are traditionally considered to be dimensional (e.g., when quantifying intelligence by a standardized test score) rather than categorical (distinguishing different categories such as intelligent vs. unintelligent). When considering a categorical construct, such as Down syndrome, on the other hand, the characteristic is qualitative (groups are classified by existence or absence of an extra chromosome) rather than quantitative (varying degrees of Down syndrome). The group bound together by the possession of a certain characteristic (disease, d…

Statistical methods for the evaluation of university systems

2011

Coarse-Graining Intermolecular Interactions in Dispersions of Highly Charged Colloids

2012

International audience; Effective pair potentials between charged colloids, obtained from Monte Carlo simulations of two single colloids in a closed cell at the primitive model level, are shown to reproduce accurately the structure of aqueous salt-free colloidal dispersions, as determined from full primitive model simulations by Linse et al. (Linse, P.; Lobaskin, V. Electrostatic Attraction and Phase Separation in Solutions of Like-Charged Colloidal Particles. Phys. Rev. Lett.1999, 83, 4208). Excellent agreement is obtained even when ion-ion correlations are important and is in principle not limited to spherical particles, providing a potential route to coarse-grained colloidal interactions…