Effect of Pressure on Structural, Elastic and Electronic Properties of Perovskite PbTiO3

We study the effect of pressure on Structural, elastic and electronic properties of Cubic and Tetragonal Perovskite using density function theory. The equilibrium parameters obtained are in good agreement with the available literature both experimental and theoretical. We found out that there is transition from tetragonal to cubic at a pressure of around 30GPa. Both crystals are stable in the pressure range of this study (0 – 50 GPa), and the stability increases with increasing pressure. The bulk modulus (B), Young modulus (E) and Shear modulus (G) all increase with increasing pressure. The band-gap increases and decrease around (X-Gamma) and (M-Gamma) for the case of Cubic and decrease for the case of Tetragonal Crystal around (X-Gamma), (Z-Gamma) and (Z-X) which converges at pressure of around 30GPa

The Effect of Varying Soot Concentration and Relative Humidity on Visibility and Particle Size Distribution in Urban Atmosphere

This research used extracted extinction coefficients and common mode radii of urban aerosols to carry out visibility simulations at corresponding spectral wavelengths from 0.4-0.8µm from the improved version of the Optical Properties of Aerosols and Clouds (OPAC 4.0) data at eight relative humidities (RH) (0%, 50%, 70%, 80%, 90%, 95%, 98% and 99% RH). Five models of the urban aerosols used comprised of insoluble (INSO), Water-soluble (WASO) and Soot (Black Carbon). From the average concentration set up by OPAC 4.0, the concentrations of the Soot (Black Carbon) were varied by external mixing. The Angstrom exponent (α), the curvature (α2) and the urban atmospheric turbidity (β) were obtained from the regression analysis of the first and second order polynomial of Kaufman’s representation of the Koschmieder equation for atmospheric visibility. The mean exponents of the aerosol size growth curve (µ) were determined from the aerosol effective hygroscopic growth ( ) while the humidification factors (γ) were determined from the visibility enhancement factors f(RH,λ). With µ and γ, the mean exponents of aerosol size distributions (υ) were determined for all the models. It was observed that at varying Soot (Black Carbon) concentrations and RH there were non-linear relationships between them and visibilities. The values of α > 1 showed the presence of fine mode particles from the WASO part of the aerosol mixture and α2 being positive indicated bimodal aerosol particle distributions. Additionally, visibility deterioration is predicted because of the increase in turbidity (β) with the variation of Soot and RH

Isochronous and Unexpected Behavior for Complex-Valued Non-linear Oscillators with Parametric Excitation

Usually oscillators with periodic excitations show a periodic motion with frequency equal to the forcing one. A complex-valued nonlinear oscillator under parametric excitation is investigated by an asymptotic perturbation method based on Fourier expansion and time rescaling. Four differential equations for two nonlinearly coupled oscillators are derived. Approximate solutions are obtained and their stability is discussed. We found that the resulting motion is periodic with a frequency equal to the forcing one, if appropriate inequalities are satisfied and then for a large parameter range. The system is isochronous because periodic solutions are possible in a well-defined phase region and not only for certain discrete values. Moreover, we demonstrate that if we insert a gyroscopic term the motion can be always periodic for a well-defined parameter range but with a frequency different from the forcing frequency. Analytic approximate solutions are checked by numerical integration

Physical model of dimensional regularization II: complex dimensions, non-scalar fields and the cosmological constant

In an earlier paper on the foundations of dimensional regularization, I formulated a model of a scalar quantum field whose propagator exhibits short-distance power-law screening with real positive exponent.  In this paper, I heuristically generalize the model so that the propagator exhibits power-law screening at short distance with complex exponent.  I further extend the model to Abelian gauge fields and Dirac spinors.  As an unexpected byproduct, the spinor case leads to interesting extensions of the “bag” boundary conditions for the Dirac and Weyl equations.  If the world really had complex dimension, it might explain in a natural way why the preponderance of observed fundamental interactions are renormalizable; and why the non-renormalizability of quantum gravity, which balances dimensional-regularization poles against a very weak coupling constant, is both acceptable and too small to be observed under ordinary circumstances. It might also motivate the famous factor of 10-120 between the observed cosmological constant and naïve dimensional analysis

Confinement and Asymptotic Freedom in a Purely Geometric Framework

The most important properties of strong interactions, confinement and asymptotic freedom, can be explained in a purely geometric way, using a non-local modification of the general relativity. At the same time, the dichotomy matter-field of the Einstein equation is eliminated and the physical world is described only by means of a unified field. Hadrons can be identified with “strong” black holes. The uncertainty principle emerges naturally in this model as consequence of the non-local modification of the General Relativity

On a Peculiar Attractor for Weakly Nonlinear Oscillators with a Two Period Quasiperiodic Forcing

We study a very peculiar nonlinear oscillator with an external two period quasiperiodic excitation, being the golden mean the ratio between the two frequencies. The two period quasi periodic forcing is characterized by an infinite frequencies number. As a consequence, we find that the motion settles down in a two period quasi periodic atttractor for a wide excitation amplitude range. The competition between the two frequencies does not produce a closed curve but fills a well defined phase space region in the Poincarè section. This attractor somehow resembles strange nonchaotic attractors because both are characterized by quasiperiodic forcing. Using a suitable perturbation method, we can understand the new attractor most important characteristics and find an approximate solution for its dynamical behavior. Numerical simulations are used to check out the analytical investigation

Hidden mass and dark matter

It is shown that the substance which is impossible to record in any spectra of electromagnetic radiation, which manifests itself in space only through gravity, cannot be considered a new, previously unknown type of matter – "black matter". The fundamental, unsolvable problems with this approach are demonstrated. The unrecorded substance is a common baryonic substance that makes up the "hidden mass". It has been hypothesized that the bulk of the hidden mass consists of asteroids composed of solid hydrogen. Their formation took place as a result of explosions of the first generation stars (the population III stars) during the gravitational compression of hydrogen clouds in the warm-hot phase, accompanied by self-cooling due to losses associated with electromagnetic radiation. The paper shows at what ratios of physical parameters a similar process is triggered and its physical essence is explained. The possibility of yet another previously unknown direction of spontaneous gravitational compression is shown: compression with self-heating of small mass clouds, resulting in the formation of structures with a degenerate electron gas, including unstable ones. A separate chapter of this work is devoted to a discussion of the problems of the hot Universe model, on which the Big Bang model and the ΛCDM model are based

Evaluation of Computed Tomography doses in three medical diagnostic centres in Kano

Computed tomography (CT), is an X-ray procedure that generates high quality cross-sectional images of the body, and by comparison to other radiological diagnosis, the use of CT in medical diagnosis delivers radiation doses to patients that are higher than those from other radiological procedures. Lack of optimized protocols could be an additional source of increased dose in developing countries. The aim of this study is to conduct radiation doses survey for head, chest and abdomen CT examinations of patients in three selected CT Diagnostics centers in Kano city. Detailed were obtained for 144 CT examinations for adult patients only. The results from the three Diagnostics centers (hospitals) were compared with each other as well as with the IAEA guidance level for this particular investigation.  Survey of radiation doses were carried out by calculating Volume dose index (CTDIvol), and dose length product (DLP) using the SPSS software program. The study showed that the mean DLP of the one Diagnostics center (hospital) is 1522.6 mGy.cm which is far much higher than the two other diagnostic centers Mohammed Abdullahi Wase which stands at 661.0 mGy.cm, Providian medical diagnostic center which stand at 1121.3 mGy.cm as well as higher than the IAEA level which is 527 mGy.cm. The study showed that the mean CTDIvol for patients in AKTH is 38.6 mGy which again is higher than the two other diagnostic centers Mohammed Addullahi Wase which is 9.5 mGy, Providian medical diagnostic center is 9.6 mGy though, it is less than the IAEA level which is 47.0 mGy. This study showed that there is an urgent need for optimizing patient doses in Kano city CT examinations. This can be ensured by providing training and retraining for workers and conducting quality control measurements and preventive maintenance regularly so as to detect any unnecessary outflow of ionization radiation early enough before they negatively affect the image which may necessitate re-imaging and then increase patients’ dose

Superconducting State Parameters of IN(1-x)Tl(x) Binary Alloys

A universal model potential of Fiohais et al. with five local field correction functions due to Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used for the first time to study the superconducting state parameters viz. electron-phonon coupling strength, Coulomb pseudopotential, transition temperature, isotope effect exponent and effective interaction strength of binary alloys. Very strong effect of the various local field correction functions is established from the present study. The comparison with other such theoretical values is promising, which confirms the applicability of model potential in clarifying the superconducting natures of binary mixture

Curvature and the Electromagnetic Field

Maxwell’s equations are derived from the curvature tensor and a vector potential. The results are combined with Einstein’s equations.  Complete solutions to the resulting equation yield simultaneous solutions to both Einstein’s and Maxwell’s equations. This is a classical theoretical unification of electromagnetism and gravitation