Showing papers in "Canadian Journal of Physics in 2000"
TL;DR: In this paper, two standard physics problems are solved in terms of the Lambert W − function, to show the applicability of this recently defined function to physics, and the problems solved concern Wien's displacement law and the fringing fields of a capacitor, the latter problem being representative of some problems solved using conformal transformations.
Abstract: Two standard physics problems are solved in terms of the Lambert W function, to show the applicability of this recently defined function to physics. Other applications of the function are cited, but not described. The problems solved concern Wien's displacement law and the fringing fields of a capacitor, the latter problem being representative of some problems solved using conformal transformations. The physical content of the solutions remains unchanged, but they gain a new elegance and convenience. PACS No.: 41.10F
271 citations
TL;DR: In this paper, the authors consider different options for the search for possible variations of the fundamental constants in both time and space in the range 1081010 years and give a brief overview of the results obtained with several methods.
Abstract: We consider different options for the search for possible variations of the fundamental constants. We give a brief overview of the results obtained with several methods. We discuss their advantages and disadvantages with respect to simultaneous variations of all constants in both time and space in the range 1081010 years. We also suggest a few possibilities for the laboratory search. Particularly, we propose some experiments with the hyperfine structure of hydrogen, deuterium, and ytterbium171 and of some atoms with a small magnetic moment. Other suggestions are for some measurements of the fine structure associated with the ground state. Special attention is paid to the interpretation of the hfs measurements in terms of variations of the fundamental constants. PACS No.: 31.30G
95 citations
TL;DR: In this article, the authors examine the development in terms of the knowledge of teaching at U.S. universities and find that some physicists are focusing their research effort on physics education research (PER).
Abstract: At a number of U.S. universities, some physicists are focusing their research effort on physics education research (PER). This paper examines this development in terms of the knowledge of teaching ...
87 citations
TL;DR: In this paper, the potential energy has been calculated over a wide range of internuclear distance for 28 lowest molecular states of LiCs, 32 lowest states of NaCs, and 30 lowest state of KCs molecules.
Abstract: The potential energy has been calculated over a wide range of internuclear distance for 28 lowest molecular states of LiCs, 32 lowest states of NaCs, and 30 lowest states of KCs molecules. This calculation is done by using an ab initio method based on nonempirical pseudopotentials, parameterized l-dependent polarization potentials, and full valence configuration interaction calculations. Extensive tables of energy values versus internuclear distance are displayed at the following address http://hplasim2.univ-lyon1.fr/allouche. Molecular spectroscopic constants have been derived for the bound states with regular shape. PACS Nos.: 31.15Ar, 31.25-u
82 citations
TL;DR: Evaluation of the neutron fluence generated by the February 23, 1956 solar particle event for an aluminum-water shield- target configuration is compared with the LAHET Monte Carlo calculation for the same shield-target configuration.
Abstract: A low-energy neutron transport algorithm for use in space-radiation protection is developed. The algorithm is based upon a multiple energy group analysis of the straight ahead Boltzmann equation utilizing a mean value theorem for integrals. The algorithm developed is then verified by using a collocation method solution on the same straight ahead Boltzmann equation. This algorithm was then coupled to the existing NASA Langley HZETRN (high charge and energy transport) code through the evaporation source term. Evaluation of the neutron fluence generated by the February 23, 1956 solar particle event for an aluminum-water shield-target configuration is then compared with the LAHET Monte Carlo calculation for the same shield-target configuration. The algorithm developed showed a great improvement in results over the unmodified HZETRN solution. A bidirectional modification of the evaporation source produced further improvement of the fluence.
50 citations
TL;DR: In this article, the effect of radiation on the forced convection flow of an optically dense incompressible fluid along a heated horizontal stretching surface was determined, and the boundary-layer equations were transformed to ordinary differential equations containing a radiation parameter R*, velocity exponent parameter M, Prandtl number P r, and surface temperature parameter θ ω.
Abstract: We determine the effect of radiation on the forced convection flow of an optically dense incompressible fluid along a heated horizontal stretching surface. The boundary-layer equations are transformed to ordinary differential equations containing a radiation parameter R*, velocity exponent parameter M, Prandtl number P r, and surface temperature parameter θ ω. The effect of these parameters are studied. Graphical results for the velocity and temperature are presented and discussed. PACS Nos.: 44.40+a, 47.27-i
36 citations
TL;DR: A brief summary of underlying principles governing ultrathin film magnetic nanostructures and magnetoelectronics is presented in this paper, based more on physical intuition than on rather complex physical and mathematical models in order to bring this new and rapidly expanding field to a broad audience.
Abstract: A brief summary of underlying principles governing ultrathin film magnetic nanostructures and magnetoelectronics will be presented The presentation will be based more on physical intuition than on rather complex physical and mathematical models in order to bring this new and rapidly expanding field to a broad audience The success of this field has been based on the ability to create new structures in which interfaces play a crucial role Three major phenomena have strongly affected progress in the development of new magnetic materials based on ultrathin films: (a) interface anisotropies; ( b) interlayer exchange coupling; and (c) magneto-electron transport The great progress in the study of ultrathin film multilayers and films patterned with submicrometre lateral geometries has led to a new class of electronic devices whose operation is based upon the spin-polarized character of the electronic carriers "Magnetoelectronics and spintronics" are terms used to mark the development of very small spin-polarized electronic devices Some latest developments in magnetic sensors and magnetic RAM will be presented to emphasize the importance of spintronics in the emerging technologies of the 21st century
36 citations
TL;DR: Ball milling is an important method for the preparation of materials both for the investigation of fundamental physical properties and for a number of possible commercial applications as discussed by the authors, and it has been used in many applications.
Abstract: Ball milling is an important method for the preparation of materials both for the investigation of fundamental physical properties and for a number of possible commercial applications. In the prese...
32 citations
TL;DR: In this paper, the PMMA organic polymer laser ablation for several values of the energy flux of the XeCl laser was investigated and the results seem to support the model of volume superheating, which is associated with bubble creation, bubble association and subsequent burst.
Abstract: We present results related to the PMMA organic polymer laser ablation for several values of the energy flux of the XeCl laser. These results seem to support the model of volume superheating, which is associated with bubble creation, bubble association, and subsequent burst. It is shown that the laser ablation mode correlates well with the generated acoustic wave and the noise imposed on it that is detected by a sensitive pressure transducer located in the back of the sample.PACS Nos.: 72.20; 72.60; 42.62 cf; 81:05
31 citations
TL;DR: In this article, the behavior of cosmic rays observed by three stations during a time of high-speed solar-wind (HSSW) events was studied and the influence of the IMF (interplanetary magnetic field) associated with HSSW was also studied.
Abstract: We have studied the behavior of cosmic rays observed by three stations during a time of high-speed solar-wind (HSSW) events. These stations cover the median rigidity range 16-164 GV. The influence of the IMF (interplanetary magnetic field) associated with HSSW has also been studied. Our analysis covers the period 1967-1986. Both the cosmic-ray intensity and geomagnetic activity are enhanced by coronal-mass-ejection events. The IMF magnitude and fluctuation are responsible for the depression of cosmic-ray intensity during HSSW events. This depression is rigidity dependent. Low-energy cosmic rays suffer more intensity depression. The rigidity spectrum of the cosmic-ray intensity decreases is dependent upon the phase of the solar cycle. It was steeper during the period 1979-1980. The power exponent is dependent upon the magnetic state of the solar cycle in support of the prediction of the drift model. PACS Nos.: 96.50Ci, 96.40-z
27 citations
TL;DR: An all-fiber 1.48 µm generator based on a LD-pumped Yb-doped double-clad laser and cascaded Raman wavelength converter has been developed in this article.
Abstract: An all-fiber 1.48 µm generator based on a LD-pumped Yb-doped double-clad laser and cascaded Raman wavelength converter has been developed. Second-order Raman Stokes radiation was generated in a phosphosilicate-fiber resonator formed by two pairs of Bragg gratings. The Yb-doped double-clad fiber laser was pumped by seven laser diodes combined via a low-loss fused fiber coupler and provided 4.4 W at 1.06 µm at the input of the Raman converter. A slope efficiency of the Raman converter of 40% with respect to the power emitted by the double-clad Yb laser has been achieved. We obtained an output power of 1.5 W with a total optical-to-optical efficiency of 21%. It was found that four-wave mixing, initiated in the fiber by the high-intensity light, results in spectral broadening of the 1.48 µm radiation and leaking of the first-Stokes radiation from the resonator formed by the 1.24 µm Bragg gratings, thus reducing the efficiency of the first-to-second-Stokes conversion.PACS No.: 42.55Wd
TL;DR: Experimental results have shown that P-doped fiber is the most radiation-sensitive of the fibers tested and that dose rates have no influence on a fiber optic dosimeter operating at this wavelength.
Abstract: Ge-doped, P-doped, normal single-mode (SM) and multimode (MM) optical fibers were exposed to Cobalt-60 gamma radiation at dose rates of 0.5 and 3.0 Gy/min, typical radiotherapy dose rates. A CCD-based fiber optic spectrometer was used to measure the real-time absorption spectra of these fibers in the visible region. Experimental results have shown that P-doped fiber is the most radiation-sensitive of the fibers tested. At the wavelength of 502 nm, the radiation-induced loss in P-doped fiber shows a linear relationship with the total dose with no dose-rate dependence. This indicates that dose rates have no influence on a fiber optic dosimeter operating at this wavelength. The radiation-induced losses in normal MM fibers, Ge-doped MM fibers, and Ge-doped SM fibers are shownto be dose-rate dependent. PACS No.: 42.62nBe, 42.81-i
TL;DR: The fluid analogy is extended to time-dependent phenomena, in particular, to the analysis of cellular pattern evolution in the course of spreading to measure tissue surface tension and viscoelastic properties.
Abstract: Early embryonic development is characterized by spectacular morphogenetic processes such as sorting or spreading of tissues. Analogy between viscoelastic fluids and certain properties of embryonic tissues turned out to be useful in interpreting some aspects of these morphogenetic phenomena. In accordance with the differential adhesion hypothesis, the values of tissue-specific surface tensions have been shown to be consistent with the equilibrium configurations such tissues reach in the course of sorting and spreading. A method to measure tissue surface tension and viscoelastic properties is described. Notions like the Laplace's equation relating surface tension to radii of curvature, or the Kelvin model of viscoelasticity are used to analyze the results of these measurements. The fluid analogy is extended to time-dependent phenomena, in particular, to the analysis of cellular pattern evolution in the course of spreading. On the basis of recent experimental findings, we demonstrate that the kinetics of spr...
TL;DR: A simplified version of a previously proposed model is presented and used to illustrate the salient features of the motion of a slowly rotating curling rock as mentioned in this paper, and a one-parameter model was presented.
Abstract: A simplified version of a previously proposed model is presented and used to illustrate the salient features of the motion of a slowly rotating curling rock. A one-parameter model is presented. Ana...
TL;DR: In this paper, the shifted 1/N expansion method for constrained quantum mechanical systems with spherically symmetric potentials was formulated and applied to constrained HPC systems with bounded sparseness.
Abstract: In this paper we formulate the shifted 1/N expansion method for constrained quantum mechanical systems with spherically symmetric potentials. As an example, we apply our technique to the confined H...
TL;DR: In this paper, the effect of radiation on forced convection flow of a micropolar fluid over a horizontal plate was investigated and the governing nonsimilar boundary-layer equations were solved using the cubic spline col...
Abstract: We determine the effect of radiation on forced convection flow of a micropolar fluid over a horizontal plate. The governing nonsimilar boundary-layer equations are solved using the cubic spline col...
TL;DR: In this paper, a theoretical study of the pulsed electromagnetic radiation from a vertical magnetic dipole placed on a plane-conducting earth is presented, where the application of a Laplace transformation in time and a Fourier transformation in the two orthogonal, horizontal, spatial components leads, under consideration of initial, boundary, and transition conditions, to an integral representation of the solution of the wave equation in frequency space.
Abstract: A theoretical study of the pulsed electromagnetic radiation from a vertical magnetic dipole placed on a plane-conducting earth is presented. The application of a Laplace transformation in time and a Fourier transformation in the two orthogonal, horizontal, spatial components leads, under consideration of initial, boundary, and transition conditions, to an integral representation of the solution of the wave equation in frequency space. A modified Cagniard method is then used to derive closed-form expressions for the magnetic Hertz vector anywhere above the conducting earth. The method is used to perform numeric calculations of the magnetic Hertz vector, for different source-receiver distances, as well as different values of the earth's conductivity and permittivity. PACS Nos.: 41.20Jb, 42.25Bs, 42.25Gy, 44.05+e
TL;DR: In this paper, the relativistic configuration-interaction method and perturbation theory were used to evaluate the second order hyperfine splitting in lithium-like ions, and the nuclear magnetization distribution effect on the interelectronic interaction correction of the first order in 1/Z was evaluated.
Abstract: The interelectronic-interaction corrections of the second order in 1/Z to the ground-state hyperfine splitting in lithiumlike ions are evaluated. The calculations are performed by using the relativistic configuration-interaction method and perturbation theory. In addition, the nuclear magnetization distribution effect on the interelectronic-interaction correction of the first order in 1/Z is evaluated within the single-particle nuclear model. The calculations provide an improvement in the theoretical predictions for the hyperfine splitting in lithiumlike ions. PACS Nos.: 31.30Gs, 31.30Jv
TL;DR: In this article, the optical properties of Tm3+-doped KY3F10 were examined for the first time and the laser possibilities offered by Tm 3+doped k-thulium ion were examined.
Abstract: We examine the laser possibilities offered by Tm3+-doped KY3F10. After crystal growth and X-ray diffraction analysis, the optical properties of thulium ions in KY3F10 are determined for the first t...
TL;DR: In this article, the I'1Πg outer well state of HD has been studied using a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, where rovibronic levels are populated and probed by pulsed lasers.
Abstract: We report on a study of the I'1Πg outer well state of HD. Via a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, rovibronic levels (v = 0-2, J = 1-4) are populated and probed by pulsed lasers. Level energies are measured with an accuracy of 0.03 cm-1. Due to gerade-ungerade symmetry breaking, the long-range behavior of the I' potential in HD deviates from that of H2 and D2. When this deviation is taken into account a semi-empirical potential for the I'1Πg state may be constructed, resulting in better agreement with the observed level energies than derived from an adiabatic ab initio potential. With this new potential it is predicted that the I' well can sustain only 4 vibrational levels, with the v = 3 level having a binding energy of 1.38(3) cm-1. PACS Nos.: 33.80.Rv, 34.20.Cf, 33.20.Ni, 31.50.+w
TL;DR: In this paper, the authors report on the observation of coherent excitation and spectroscopy performed using Ramsey's method of separated excitation fields on a single trapped and laser cooled ion of strontium.
Abstract: We report on the observation of coherent excitation and spectroscopy performed using Ramsey's method of separated excitation fields on a single trapped and laser cooled ion of strontium. Single pulse Rabi excitation studies of the ion have shown linewidths approaching the transform limited value. Studies of transition rate versus pulse duration have shown a quadratic initial increase in transition rate with a duration consistent with coherent excitation and a rapid loss of Rabi oscillations, consistent with the concept of a dephasing of the thermally populated trap oscillator states as the excitation evolves. When two-pulse Ramsey excitation is applied to the single ion, fringe widths down to a linewidth of 840 Hz (FWHM) were observed with measured fringe contrasts consistent with a probe laser linewidth of 500 Hz.PACS Nos.: 32.80Qk, 32.30Jc, 06.30Ft
TL;DR: In this article, the steady laminar flow of an incompressible viscous electrically conducting non-Newtonian fluid of second grade impinging normal to a plane wall with heat transfer is investigated.
Abstract: The steady laminar flow of an incompressible viscous electrically conducting non-Newtonian fluid of second grade impinging normal to a plane wall with heat transfer is investigated. An externally applied uniform magnetic field is applied normal to the wall, which is maintained at a constant temperature. A numerical solution for the governing momentum and energy equations is obtained. The effect of the characteristics of the non-Newtonian fluid and the magnetic field on both the flow and heat transfer is outlined. PACS Nos.: 47.50 and 47.15
TL;DR: In this paper, the authors evaluate three two-loop three-point scalar integrals, with five and six massless propagators, with specific external kinematic configurations (two legs on-shell), and four three-loop two-point integrals.
Abstract: The well-known D-dimensional Feynman integrals were shown, by Halliday and Ricotta, to be capable of undergoing analytic continuation into the domain of negative values for the dimension of space-time. Furthermore, this could be identified with Grassmannian integration in positive dimensions. From this possibility follows the concept of negative-dimensional integration for loop integrals in field theories. Using this technique, we evaluate three two-loop three-point scalar integrals, with five and six massless propagators, with specific external kinematic configurations (two legs on-shell), and four three-loop two-point scalar integrals. These results are given for arbitrary exponents of propagators and dimension, in Euclidean space, and the particular cases compared to results published in the literature. PACS Nos.: 02.90+p, 11.15Bt, 12.38Bx
TL;DR: In this paper, a nonperturbative method for tracing light rays in a transparent refractive medium in the general relativistic environment is presented, which allows for numerical analysis of a nonlinear superposition of gravitational and refractive lensing, when neither of the two effects can be treated as a small perturbation.
Abstract: The frequency-sensitive extremum principle for propagation of light rays in the geometrical optics regime is used to develop a nonperturbative method for tracing light rays in a transparent refractive medium in the general relativistic environment. The general formulation of the theory is given first; it allows for the numerical analysis of a nonlinear superposition of gravitational and refractive lensing, when neither of the two effects can be treated as a small perturbation. The scope of the general theory is gradually narrowed to the Schwarzschild field, the spherical symmetry of the refractive properties of the medium, and the small deflection regime approximation. A simple, analytically solvable example of deflection of light rays by a mass embedded in a refractive medium is considered in detail; in a vacuum, deflection of light rays by the Sun is reproduced.PACS Nos.: 42.15-i, 04.20-q, 98.90+s
TL;DR: In this article, a second quantized theory of spin-1/2 tachyons in the time-energy representation is proposed, which is Lorentz invariant without inverting the spin-statistics relationship and without introducing indefinite pseudotachyonic states.
Abstract: Dirac spinors for spin-1/2 free tachyons are derived from the Dirac and Klein-Gordon equations in terms of the standard helicity representation of the Poincare group and superluminal transformations (SLTs). It is shown that the proposed theory of second quantization is Lorentz invariant without inverting the spin-statistics relationship and without introducing indefinite pseudotachyonic states. Second quantized theory of spin-1/2 tachyons in the time-energy representation shows that tachyons are localized in time and that the most natural space for the description of tachyons is T4-space. It has been emphasized that on passing from R4-space (bradyons) to T4-space (tachyons) via either, i.e., complex or real SLTs, tachyons behave in T4-space exactly as bradyons do in R4-space. T4-space can be visualized as an internal space for a subluminal observer while R4-space appears as an internal space for a superluminal observer. PACS Nos.: 14.80K, 03.30t
TL;DR: In this paper, the results of Raman scattering experiments on single crystals of La2xSrxCuO4 (La214) as a function of temperature and doping were reported.
Abstract: We report the results of Raman scattering experiments on single crystals of La2xSrxCuO4 (La214) as a function of temperature and doping. In underdoped compounds low-energy B1g spectral weight is depleted in association with the opening of a pseudogap on regions of the Fermi surface located near (±π, 0) and (0, ±π).The magnitude of the depletion increases with decreasing doping, and in the most underdoped samples, with decreasing temperature.The spectral weight that is lost at low energies (ω 800 cm1) is transferred to the higher energy region normally occupied by multimagnon scattering. From the normal-state B2g spectra we have determined the scattering rate Γ(ω,T) of qausiparticles located near the diagonal directions in k-space. In underdoped compounds, Γ(ω,T) is suppressed at low temperatures for energies less than Eg(x) 800 cm1. The doping dependence of both the two-magnon scattering and the scattering rate suppression suggest that the pseudogap is characterized by an energy scale Eg ~ J, where J i...
TL;DR: In this paper, a review highlights the developments that have taken place in the field of high-resolution Raman spectroscopy of gases from the pioneering studies of Stoicheff and Welsh in the early fifties to the early nineties.
Abstract: This review highlights the developments that have taken place in the field of high-resolution Raman spectroscopy of gases from the pioneering studies of Stoicheff and Welsh in the early fifties to ...
TL;DR: In this article, the average multiplicities of the emitted secondary charged particles for total disintegration were investigated and the results showed that the multiplicity distributions of relativistic charged particles agree with the Gaussion distribution.
Abstract: The interactions of 4.5 A GeV/c 24Mg and 32S nuclei with emulsion were studied. The experimental inelastic mean free path for these interactions is compared with theoretically calculated values. The average multiplicities of the emitted secondary charged particles for total disintegration were investigated. Total disintegration events are analysed to investigate the characteristics of secondary charged particles produced in such collisions. The results show that the multiplicity distributions of relativistic charged particles agree with the Gaussion distribution. The average multiplicity of grey and black particles is in good agreement with the prediction of the fireball model. The probabilty of total disintegration of Ag(Br) nuclei by different projectiles is nearly independent of the incident energy. PACS No.: 25.70
TL;DR: In this paper, a small polaron hopping theory was used to analyze the DC electrical conductivity of glasses containing iron chloride and confirmed nonadiabatic hopping regime between Fe ions.
Abstract: DC electrical conductivity measurements of Fe2O3K2OP2O5 glasses containing iron chloride have been carried out in the temperature range from room temperature to 360°C. The DC conductivity was analyzed in terms of small polaron hopping theory. The hopping regime between Fe ions was confirmed to be nonadiabatic. The increase in the conductivity was of the same order of magnitude as the change in the pre-exponential factor upon increasing the FeCl3 content. The decrease in the activation energy with increasing FeCl3 content was interpreted in terms of a decrease in the distance between the iron sites. The increase in electrical conductivity was ascribed to the difference in the activation energy. The variation in the conductivity parameters was interpreted in terms of the structural changes that take place upon increasing the FeCl3 content of the glasses. PACS No.72.20Ee
TL;DR: In this paper, the authors report results obtained with the Maryland Physics Expectations (MPEX) survey in: (a) a course for students who have not previously taken a second course in physics in high school; (b) physics for the life sciences; (c) honors physics; and (d), physics for engineers.
Abstract: We report results obtained with the Maryland Physics Expectations (MPEX) survey in: (a) a course for students who have not previously taken a second course in physics in high school; (b) physics for the life sciences; (c) honors physics; and (d) physics for engineers. Comparing the responses with a group of experienced teachers Redish et al. call the ``expert group'', we find that (i) overall, agreement with experts decreased after the two semesters of instruction, and (ii) there were significant differences between the response patterns for students in the first two courses, compared with the last two. The data suggest that the context of learning, i.e., a program in physical science versus one in the life sciences must be taken into account in research on students' beliefs about learning physics. PACS No.: 01.40Fk