Assessment of geogenic natural radionuclides contents of soil samples collected from Ogun State, Southwestern Nigeria.

Background: Natural radionuclides are always present in the environment. Human exposure to the background radiation is inevitable. It is therefore important to assess health risk associated with these radionuclides. Materials and Methods: The distribution of natural radionuclides 238U, 232Th and 40K in soil samples collected from all the twenty (20) local Governments headquarter areas in Ogun state, Nigeria were determined by gamma spectroscopy using a high-purity germanium detector. The measured concentrations were used in estimating the radiological risk pose to people living in these communities. Results: The activity concentrations measured ranged between 3 ± 1 Bqkg-1(Otta) to 27 ± 6 Bqkg-1(Odeda) for 238U, 10 ± 1 Bqkg-1(Otta) to 126 ± 6 Bqkg-1(Ijebu Igbo) for 232Th and 7 ± 6 Bqkg-1(Aiyetoro) to 497 ± 1 Bqkg-1(Odeda) for 40K. The mean radium equivalent calculated was 77.6 Bqkg-1 which is lower than 370 Bqkg-1 of the world average and the hazard indices calculated were lower than unity. Conclusion: The absorbed rate and annual effective dose estimated for most of the locations are in good agreement with world average values except for Akomoje, Ake-Abeokuta, Ogere, Ijebu-Igbo and Odeda

Assessment of geogenic natural radionuclide contents of soil samples collected from Ogun State, South western, Nigeria

Background: Natural radionuclides are always present in the environment. Human exposure to the background radia�on is inevitable. It is therefore important to assess health risk associated with these radionuclides. Materials and Methods: The distribu�on of natural radionuclides 238U, 232Th and 40K in soil samples collected from all the twenty (20) local Governments headquarter areas in Ogun state, Nigeria were determined by gamma spectroscopy using a high-purity germanium detector. The measured concentra�ons were used in es�ma�ng the radiological risk pose to people living in these communi�es. Results: The ac�vity concentra�ons measured ranged between 3 ± 1 Bqkg-1(O0a) to 27 ± 6 Bqkg-1(odeda) for 238U, 10 ± 1 Bqkg-1(O0a) to 126 ± 6 Bqkg-1(Ijebu Igbo) for 232Th and 7 ± 6 Bqkg-1(Aiyetoro) to 497 ± 1 Bqkg-1(Odeda) for 40K. The mean radium equivalent calculated was 77.6 Bqkg-1 which is lower than 370 Bqkg-1 of the world average and the hazard indices calculated were lower than unity. Conclusion: The absorbed rate and annual effec�ve dose es�mated for most of the loca�ons are in good agreement with world average values except for Akomoje, Ake-Abeokuta, Ogere, Ijebu-Igbo and Odeda

Isotropic representation of noncommutative 2D harmonic oscillator

We show that 2D noncommutative harmonic oscillator has an isotropic representation in terms of commutative coordinates. The noncommutativity in the new mode, induces energy level splitting, and is equivalent to an external magnetic field effect. The equivalence of the spectra of the isotropic and anisotropic representation is traced back to the existence of SU(2) invariance of the noncommutative model.Comment: 15 pages, RevTex4, no figures; article format, improved version of the previous paper; new references and aknowledgements adde

Transition Prediction in Hypersonic Boundary Layers Using Receptivity and Freestream Spectra

Boundary-layer transition in hypersonic flows over a straight cone can be predicted using measured freestream spectra, receptivity, and threshold values for the wall pressure fluctuations at the transition onset points. Simulations are performed for hypersonic boundary-layer flows over a 7-degree half-angle straight cone with varying bluntness at a freestream Mach number of 10. The steady and the unsteady flow fields are obtained by solving the two-dimensional Navier-Stokes equations in axisymmetric coordinates using a 5th-order accurate weighted essentially non-oscillatory (WENO) scheme for space discretization and using a third-order total-variation-diminishing (TVD) Runge-Kutta scheme for time integration. The calculated N-factors at the transition onset location increase gradually with increasing unit Reynolds numbers for flow over a sharp cone and remain almost the same for flow over a blunt cone. The receptivity coefficient increases slightly with increasing unit Reynolds numbers. They are on the order of 4 for a sharp cone and are on the order of 1 for a blunt cone. The location of transition onset predicted from the simulation including the freestream spectrum, receptivity, and the linear and the weakly nonlinear evolutions yields a solution close to the measured onset location for the sharp cone. The simulations over-predict transition onset by about twenty percent for the blunt cone

Spatial Stability of Incompressible Attachment-Line Flow

Linear stability analysis of incompressible attachment-line flow is presented within the spatial framework. The system of perturbation equations is solved using spectral collocation. This system has been solved in the past using the temporal approach and the current results are shown to be in excellent agreement with neutral temporal calculations. Results amenable to direct comparison with experiments are then presented for the case of zero suction. The global solution method utilized for solving the eigenproblem yields, aside from the well-understood primary mode, the full spectrum of least-damped waves. Of those, a new mode, well separated from the continuous spectrum is singled out and discussed. Further, relaxation of the condition of decaying perturbations in the far-field results in the appearance of sinusoidal modes akin to those found in the classical Orr-Sommerfeld problem. Finally, the continuous spectrum is demonstrated to be amenable to asymptotic analysis. Expressions are derived for the location, in parameter space, of the continuous spectrum, as well as for the limiting cases of practical interest. In the large Reynolds number limit the continuous spectrum is demonstrated to be identical to that of the Orr-Sommerfeld equation

Interacting new generalized Chaplygin gas

We have presented a model in which the new generalized Chaplygin gas interacts with matter. We find that there exists a stable scaling solution at late times in the evolution of the universe. Moreover, the phantom crossing scenario is observed in this model.Comment: 16 pages, 6 figures, accepted for publication in Int. J. Theor. Phy

International Review and Advisory Committee

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