On Shirokov's “One New Effect of the Einsteinian theory of Gravitation”

In this note we study M.F. Shirokov's One New Effect of Einstein's theory of Gravitation in the Kerr field. We confine ourselves to a circular trajectory (r=const) in the plane=/2. In the limit that terms of the second order and higher ina/r (a is the angular momentum per unit mass) are negligible we find an additional shift betweenT andT _r (orT ) of amount –(8a/r)(m/r) ^3/2. Thus vibrations lie further behindr(or) vibrations in this case than in the Schwarzschild field.     

Ring-opening polymerization of ε-caprolactone by lithium piperazinyl-aminephenolate complexes: synthesis, characterization and kinetic studies

A series of lithium complexes were prepared from 2(N-piperazinyl-N'-methyl)-2-methylene-4-R'-6-R-phenols ([ONN](RR')) and characterized through elemental analysis, (1)H and (13)C{(1)H} NMR spectroscopy, and X-ray crystallography. Treatment of the ligands with n-butyllithium afforded {Li[ONN](RR')}(3) [R = Me, R' = (t)Bu, (1); R = R' = (t)Bu (2); R = R' = (t)Am, (3), (t)Am = C(CH(3))(2)CH(2)CH(3)], with trimetallic structures in the solid-state as shown by single-crystal X-ray diffraction. The reactivity of these complexes in the ring-opening polymerization of ε-caprolactone (ε-CL), as well as the influences of monomer concentration, monomer/Li molar ratio, polymerization temperature and time, was studied. Rates of polymerization were first order with respect to both monomer and lithium concentrations, and activation energies for the reactions were determined. MALDI-TOF MS analysis revealed that transesterification had occurred during the polymerization.     

Efficient and robust estimation for autoregressive regression models using shape mixtures of skewt normal distribution

Multiple linear regression model based on normally distributed and uncorrelated errors is a popular statistical tool with application in various fields. But these assumptions of normality and no serial correlation are hardly met in real life. Hence, this study considers the linear regression time series model for series with outliers and autocorrelated errors. These autocorrelated errors are represented by a covariance-stationary autoregressive process where the independent innovations are driven by shape mixture of skew-t normal distribution. The shape mixture of skew-t normal distribution is a flexible extension of the skew-t normal with an additional shape parameter that controls skewness and kurtosis. With this error model, stochastic modeling of multiple outliers is possible with an adaptive robust maximum likelihood estimation of all the parameters. An Expectation Conditional Maximization Either algorithm is developed to carryout the maximum likelihood estimation. We derive asymptotic standard errors of the estimators through an information-based approximation. The performance of the estimation procedure developed is evaluated through Monte Carlo simulations and real life data analysis.

     

Heavy metal levels and physico--chemical quality of potable water supply in Warri, Nigeria

The interaction between man's activities and the environment is gaining world wide attention. Warri an oil producing community in Delta State of Nigeria is faced with environmental oil pollution. Since open and underground water bodies are regarded as final recipients of most environmental pollutants, this study sought to provide data on the levels of the physico-chemical parameters and contaminants in Warri metropolitan water supply. This study investigated the cadmium, lead and chromium using Atomic Absorption Spectrophotometer, physico-chemical properties such as pH, temperature, total suspended solid TSS, total dissolved solid TDS, electrical conductivity EC, biological oxygen demand BOD, dissolved oxygen DO, chemical oxygen demand COD, and total coliform count of potable water sources in Warri. Ekpan River was found to have 1.2 mg/L of cadmium, 1.0 mg/L of chromium, 1.20 mg/L of lead and 2.0 mg/L of manganese. The heavy metals levels and the pollution parameters were lowest in the borehole water samples, except pH which is more acidic in borehole water samples and conductivity which is more in well water samples in all the sampling stations. Some of the parameters were above WHO standards.     

Charged fluid sphere in general relativity

In this paper a solution for the interior metric of a uniformly charged static fluid sphere has been obtained. The model sphere obtained has a physically reasonable equation of state. It is found that both the central density and the pressure become infinite when=2/5(1+). Here=m ₀/r ₀: =Q ₀ ² /r ₀ ² m ₀,r ₀ andQ ₀ are, respectively, the mass, radius, and charge of the sphere. In the limit0 the solution becomes identical to the Adler solution.     

Charged static fluid spheres in Einstein-Cartan theory

We give exact interior solutions of the Einstein-Cartan equations describing charged perfect fluid distribution in general relativity. Results previously unknown for the uncharged case are deduced and we find that the pressure is discontinuous at the boundary of the fluid sphere.     

Students’ degree project as an efficient test discriminator

The problem is considered of determining how a degree examination project, which consumes a very significant proportion of the time of the student and his supervisor, affects his overall degree performance, and discriminates among students of varying performance, particularly at the university level. A survey sampling method for data collection and techniques for analysis are discussed, and results show the degree project to be a poor discriminator.     

Orange Peel Biomass-derived Carbon Supported Cu Electrocatalysts Active in the CO2-Reduction to Formic Acid

We report a green, wet chemistry approach towards the production of C-supported Cu electrocatalysts active in the CO₂ reduction to formic acid. We use citrus peels as a C support precursor and as a source of reducing agents for the Cu cations. We show that orange peel is a suitable starting material compared to lemon peel for the one-pot hydrothermal synthesis of Cu nanostructures affording better Cu dispersion as well as productivity and selectivity towards formic acid. We rationalize this finding in terms of the beneficial chemical composition of the orange peel, which favors both the reduction of the Cu precursor as well as the carbon matrix. This work demonstrates new viable opportunities for the reuse of citrus waste on a rational basis.