bluuebunny/crossref_metadata_2025 huggingface dataset:
Do leptons and quarks have a common origin?
Authors: Pilot Chris
Published: April 2011

The fermionic gauge fields associated with the Q and S symmetries of the superconformal group may describe leptons and quarks once they are broken. Curiously enough they have the correct number of degrees of freedom (although not within the usual SUe(3) framework) and come in pairs, which may be an expression of SU(2) weak charge. We assume a subcanonical k1/2 behaviour for neutrinos and u, c, and t quarks. We also show how masses must be assumed for the construction of higher than bilinear forms in the neutrino and electron fields.
Performance of various integral equation formulations for numerical solution of scattering by impedance objects
Authors: Sebak A. A. , Shafai L.
Published: April 2011

Impedance boundary conditions are used to formulate integral equations for imperfectly conducting and coated objects. Both electric and magnetic type integral equations are obtained and used to formulate a combined integral equation. The accuracy of the solutions using these methods is studied and the superiority of the combined form is pointed out. The problem of internal resonances is also investigated. For both electric and magnetic integral equations, the inaccuracy of the solutions near the resonances increases with increasing surface impedance. The combined formulation is found to give stable solutions throughout. It is then used to generate scattering data for various objects, and the effect of the object parameters and the field polarization on the results is discussed.
Gravitational repulsion in the Einstein-zero-mass scalar theory
Authors: Krori K. D. , Sarmah J. C. , Goswami D.
Published: April 2011

In this paper we extend a recent work by McGruder by investigating gravitational repulsion in the Einstein-zero-mass scalar theory. We notice that in the presence of a scalar field, gravitational repulsion is possible for particle velocities lower than those required in the pure Einstein (Schwarzschild) field. The zero-mass scalar field has acquired particular importance recently because of a suggestion by Weinberg and Wilczek that there should exist a pseudoscalar boson, the so-called axion, of negligible mass. The work of Peccei and Quinn has lent further support to the idea of axions.
Mean excitation energies for stopping powers in various materials composed of elements hydrogen through argon
Authors: Wilson J. W. , Xu Y. J. , Kamaratos E. , Chang C. K.
Published: April 2011

The basic model of Lindhard and Scharff, known as the local plasma model, is utilized to study the effects of the chemical and physical state of the medium on its stopping power. Unlike previous work with the local plasma model, in which individual electron shifts in the plasma frequency were estimated empirically, the Pines correction derived for a degenerate Fermi gas is shown herein to provide a reasonable estimate even on the atomic scale. Thus, the model is moved to a completely theoretical base requiring no empirical adjustments, adjustments characteristic of past applications. The principal remaining error is in the overestimation of the low-energy absorption properties characteristic of the plasma model in the region of the atomic discrete spectrum, although higher energy phenomena are accurately represented and even excitation-to-ionization ratios are given with fair accuracy. Mean excitation energies for covalently bonded gases and solids, ionic gases and crystals, and metals are calculated using first-order models of the bonded states for which reasonable agreement with the recently evaluated data of Seltzer and Berger is obtained. Hence the methods described herein allow reasonable estimates of mean excitation energy for any physical–chemical combination of material media for stopping power applications.
Line broadening by focusing
Authors: Brito Adelsindo Liberato de , Jabs Arthur
Published: April 2011

We point out that the spectral width of a quasimonochromatic light beam broadens when the beam is focused. A quantitative formula for this broadening is derived from classical wave theory. The effect is shown to explain some experiments on laser beams done by Panarella which he explained using the ad hoc hypothesis that the frequency of the photons changes along with the intensity of the light beam. The line broadening by focusing might also contribute to gas ionization by incident light when the ionization potential is well above the mean photon energy. Remarks are made on some direct applications of the Heisenberg relations in comparison with our treatment.
Transient interference gratings and holograms in dyed plastic
Authors: Calixto Sergio , Lessard R. A.
Published: April 2011

Transient diffraction gratings were holographically made in dyed plastic by absorbing laser light. Mean energy values of 40 mJ/cm2 absorbed in a 3-mm thick layer were needed to make gratings that lasted about 10 s. The writing beams and a reading one of different wavelength were simultaneously made to fall on the plastic: the reading beam was diffracted by the grating, which produced transient diffracted beams of sufficient intensity to be seen by the naked eye or to be stored permanently by conventional photographic methods. Curves showing diffraction efficiency versus exposure with grating frequency as a parameter are presented. Applications to real-time single and double exposure holography are also discussed.
A three-body Gaussian model of solid helium
Authors: Locke Douglas P.
Published: April 2011

A simple, analytic set of three-body models is used to calculate ground state energies and single-particle distribution functions for solid 3He and 4He. Reasonable agreement with other models and experiments over a wide range of molar bolumes (10 cm3 to the liquid transition) is demonstrated.
Total and photoelectric cross sections in some rare-earth elements
Authors: Lingam S. Chandra , Babu K. Suresh , Reddy D. V. Krishna
Published: April 2011

Total photon cross sections for four rare-earth elements, Y, Gd, Dy, and Er, were measured at photon energies of 30.85, 32.1, 36.9, 52, 72.1, 81.0, 84.3, and 145.5 keV using a good geometrical setup and a single-channel scintillation spectrometer. The results of some of the elements are new. The measured total photon cross sections are compared with the theoretical compilations of Storm and Israel and the available data of earlier investigations. The scattering cross sections obtained by interpolation using the values of Hubbell et al. were subtracted from the measured total photon cross sections to obtain the total photoelectric cross sections. The total photoelectric cross sections thus derived are compared with the latest theoretical compilations of Scofield.
Quasi-Bloch functions as basis functions in graded mixed crystals
Authors: Morrow Richard A.
Published: April 2011

Approximate eigenfunctions of the one-electron Hamiltonian for slowly graded mixed crystals are sought in the spirit of the Wentzell–Kramers–Brillouin (WKB) method. First-order differential equations for these quasi-Bloch functions are derived and a condition for their validity is presented. As input we require the Bloch functions that would be present should the grading function be held constant, a condition under which the virtual crystal potential is strictly periodic and uniform. It is also shown how our results reduce to the standard WKB ones when the periodic potential is removed.
Lattice dynamics of KCN and NaCN in the antiferroelectric phase III
Authors: Fracassi Pier Francesco , Klein Michael L.
Published: April 2011

Lattice dynamics calculations are reported for the k = 0 modes of the ordered antiferroelectric phase III of solid potassium and sodium cyanides. The calculations are based on an interionic potential including electrostatic, dispersive, and repulsive interactions. The effect of these interactions on the librational modes of the system is discussed, and the results are compared with the observed Raman spectra for both materials.
Infrared spectra of GaxIn1−xSe
Authors: Saintonge G. , Brebner J. L.
Published: April 2011

Single crystals of GaxIn1−xSe have been grown in our laboratory by the Bridgman method for x ≤ 0.20 and x ≥ 0.75. Reflectivity measurements in the far infrared, with [Formula: see text], have shown that these alloys have a two-mode behaviour except for x = 0.982 where only the GaSe-like oscillator is visible. A Kramers–Kronig analysis enabled us to obtain a first evaluation of the transverse optic (TO) and longitudinal optic (LO) frequencies of the observed modes. Aχ2 fit of the reflectivity calculated from the factorized model of the dielectric constant produced a more accurate determination for these frequencies along with their respective damping constants and ε0 and εx. Reflectivity measurements for [Formula: see text] were made on indium-rich samples, but only in InSe were the results different from those for[Formula: see text]. These are interpreted as a contamination of the [Formula: see text] mode by the E′ modes, normally visible with [Formula: see text] A model proposed by Jahne for the behaviour of optical phonons in alloy systems is applied to this study and finally a review of the criteria for the one-mode and two-mode behaviour, applied to the GaxIn1−x Se system, is given.
Monopole charge quantization and the Aharonov–Bohm effect
Authors: Kunstatter G.
Published: April 2011

We present a simple derivation of the Dirac monopole charge quantization condition, making explicit use of the Aharonov–Bohm effect. Since only the asymptotic field lines of the monopole play a crucial role, this derivation clearly shows that the quantization condition must hold unless the electrically charged particle and the monopole exchange new long-range forces. In particular, this implies that Cabrera's monopole event would be consistent with Fairbank's observations of free quarks only if the monopole carried long-range (unconfined) colour-magnetic fields.
A Fourier transform treatment of the quantum mechanical two-level system in an applied electric field. I. Single field case
Authors: Grindlay J. , Mizia J.
Published: April 2011

Fourier transform techniques are used to obtain an approximate expression for the response of a quantum mechanical two-level system to a small monochromatic applied electric field. A comparison with the results of a numerical integration of the differential equations shows that the approximation is equally satisfactory close to and far from resonance. The method is easily extended to two or more applied fields.
Possible identification of sharp features in the Voyager far-infrared spectra of Jupiter and Saturn
Authors: McKellar A. R. W.
Published: April 2011

Sharp spectral features have been observed in the far-infrared spectra of Jupiter and Saturn as recorded by the Voyager spacecraft missions. These features, which occur very close to the S(0) and S(1) transition frequencies of H2, have recently been analyzed in detail by Gautier, Marten, Baluteau, and Bachet, but there has not been a fully satisfactory explanation for their origin. It is proposed here that the features, and particularly an absorption maximum at 350.5 cm−1, may be due to bound (H2)2 van der Waals dimers in the upper atmospheres of the giant planets.
Generalized isospin sum rule: an application to magnetic transitions
Authors: Montgomery John A. , Yoo Kwang-Bock , Überall Herbert , Bosco B.
Published: April 2011

Energy-weighted sum rules with separated isospin contributions for arbitrary operators and multipolarities are developed for photonuclear and electron-scattering transitions. The Kurath sum rule is contained as a special case. Applying the sum rule to magnetic dipole transitions, ensuing numerical predictions for non-self-conjugate nuclei are compared with experimental results.
Altitude dependence of the vibrational distribution of in the nightglow and the possible effects of vibrational excitation in the formation of O(1S)
Authors: McDade I. C. , Llewellyn E. J. , Greer R. G. H. , Witt G.
Published: April 2011

A simple vibrational relaxation model that reproduces the observed vibrational distribution of the [Formula: see text] Herzberg II bands in the terrestrial nightglow is used to derive the altitude profiles of the fractional populations in the individual vibrational levels. Through consideration of these profiles it is shown that if [Formula: see text] is the Barth precursor of O(1S) in the nightglow then, at least in the terrestrial atmosphere, the higher vibrational levels appear to be more effective in the Barth transfer step than the lower vibrational levels.
Pair potentials and the bonding energy of d-band metals
Authors: MacDonald A. H. , Taylor Roger
Published: April 2011

A method for decomposing the bonding energy of d-band metals into a sum of pairwise interactions between transition metal ions is presented. The dependence of these pair potentials on the configuration of the ions is examined by evaluating them for several model d-band perfect crystals (sc, bcc, Fcc, and hcp). The results indicate that these pair interactions are not extremely sensitive to the ionic configuration. This suggests that parameterizing the variation of the total energy with ionic configuration in terms of pair potentials may be meaningful for some purposes in transition metals. On the basis of our model calculations, we obtain a pairlike approximate expression for the bonding energy.
A dilatometric study of magnetic phase transitions in erbium
Authors: Genossar J. , Steinitz M. O. , Fawcett E.
Published: April 2011

As a result of a dilatometric investigation with a resolution of better than five parts per million, we can state that the Néel transition in erbium is second order. Results at the other phase transitions of erbium are also presented.
A channeling study of vacancy – solute atom complexes in irradiated aluminum crystals
Authors: Swanson M. L. , Howe L. M. , Moore J. A. , Quenneville A. F.
Published: April 2011

The irradiation-induced evolution of vacancy – solute atom complexes in Al–Sn and Al–In crystals was studied by ion channeling. The backscattering yields from host and solute atoms near the [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] channels were measured in these alloys to determine the positions of the solute atoms in the lattice. During annealing near 200 K following 4He+ irradiation at 35 K, the solute atoms trapped vacancies, thus becoming displaced from substitutional lattice sites into the characteristic interstitial positions (1/3, 1/6, 1/6)a0, (1/4, 1/4, l/4)a0, and (1/2, 1/2, 1/2)a0 surrounded by three, four, and six vacancies, respectively. Subsequent irradiation at 70 K reduced the size of these vacancy clusters. The evolution and the decay of these vacancy – solute atom complexes were measured quantitatively during irradiation and annealing.
An inverse scattering study of sinh–Gordon dynamics
Authors: Enns R. H. , Rangnekar S. S.
Published: April 2011

An inverse scattering study of sinh–Gordon dynamics is carried out for a simple illustrative example. Specifically, using an expansion approach, the complete spatial and temporal evolution of the sinh–Gordon solution in laboratory coordinates is obtained. The analytic results are in good agreement with numerical simulation.
Effects of internal potential barriers on the photocurrent decay in semiconductors
Authors: Tin C. C. , Weichman F. L.
Published: April 2011

Transient photocurrent decay experiments were carried out to study the effects of internal potential barriers, which could be due to filled traps and metallic inclusions, on the detrapping process in semiconductors. Experiments were carried out with single crystals of Cu2O, annealed in various ways, because of the ease in inducing large defects in this material. It was found that samples of Cu2O with different defect structures had different values of trapping parameters. These different values are explained in terms of barrier formation at the trapping centres. For those samples of Cu2O that contain copper precipitates, the presence of asymmetrical barriers is proposed in order to explain the difference in the trapping parameters when compared with the standard type of Cu2O.The field dependent behaviour of the detrapping time in samples of Cu2O that do not contain copper precipitates could be explained by the presence of both the Poole–Frenkel effect and the photo-impact ionization of the traps. Those samples that contain copper precipitates do not show any field dependent behaviour of the detrapping process, probably owing to the formation of internal space charge regions.
Photoconductivity of monocrystals of CdIn2S4
Authors: Vincent A. B. , Rodríguez C. E. , Joshi N. V.
Published: April 2011

Photoconductivity spectra of monocrystals of CdIn2S4, some of which were annealed in a sulphur-rich atmosphere, have been studied in order to understand the origin of the high photosensitivity. It is found that sulphur enriched CdIn2S4 shows a high photoresponse. The data presented explain observed discrepancies in the band gap values. An origin for the slow photoresponse is also examined.
The field of an accelerating black hole embedded in a magnetic universe
Authors: Krori K. D. , Barua Madhumita
Published: April 2011

In this paper, we investigate the field of an accelerating black hole embedded in a magnetic universe and present some interesting properties of the field with respect to the trapping of uncharged and charged test particles and their absorption into the black hole.
Some properties of a-Si: C films prepared by vacuum deposition with simultaneous substrate bombardment by electrons
Authors: Brodie D. E. , Moore C. J. L.
Published: April 2011

Films of a-Si:C have been prepared by vacuum deposition while the substrate was simultaneously bombarded with 1000-V electrons. Some film properties (electrical, optical) are compared for films deposited both with and without electron beam irradiation. It is concluded that the effect of the electron beam irradiation is to produce a film with a structure closer to that of an ideal random network. Some of the films are photoconducting and have undoped electrical characteristics similar to those of a-Si:H.
Effect of anisotropic tunneling through Coulomb barriers on the electron capture in semiconductors
Authors: El-Wahidy E. F.
Published: April 2011

The capture rate of hot electrons by negatively charged gold centres in n-Ge at T = 77 K is considered for the anisotropic model. Making use of the adiabatic approximation, the angular dependence of the electron tunneling factor through the Coulomb barrier surrounding the centre is determined. It is found that, for the anisotropic case, the tunneling factor is determined mainly by the smaller transverse effective mass of the electron. The obtained anisotropic tunneling factor is then used in studying the field dependence of the capture rate when the main mechanism of energy relaxation is due to electron scattering by acoustic phonons. A comparison with the isotropic case is given.
Pinwheel and herringbone structures of planar rotors with anisotropic interactions on a triangular lattice with vacancies
Authors: Harris A. B. , Mouritsen O. G. , Berlinsky A. J.
Published: April 2011

A variety of theoretical techniques, including Monte Carlo (MC), mean field theory, and spin-wave theory, are used to analyze the phase diagram of a system of planar rotors on a triangular lattice with vacancies. A simple anisotropic interaction, which mimics the electric quadrupole–quadrupole interaction for diatomic molecules confined to rotate in the plane of the surface, induces a herringbone-ordered structure for the pure (x = 1) system, whereas for x ≈ 0.75, if the vacancies are free to move, a 2 × 2 pinwheel structure is favored. For x = 0.75, MC calculations give a continuous transition with Ising exponents in agreement with renormalization group predictions for this universality class, the Heisenberg model with corner-type cubic anisotropy. Mean field theory gives the unexpected result that the pinwheel phase is stable only along the herringbone-disordered state coexistence line in the temperature versus chemical potential phase diagram. Spin-wave theory is used to show that there is, in fact, a finite domain of stability for the pinwheel phase, and a complete phase diagram, which encompasses all available information, is conjectured.
Study of a model for the main phase transition of lipid bilayers using the Kikuchi cluster method
Authors: Stein-Barana Alzira M. , Cabrera G. G. , Zuckermann M. J.
Published: April 2011

The statistical mechanics of Doniach's two-state lattice model for the main gel – liquid crystal phase transition of phospholipid bilayers is treated in a similar manner to order–disorder transformations in binary alloys and magnetic systems, using the cluster variation method developed by Kikuchi. Indeed, the analogy holds better for the latter system, since the entropy difference between the two states gives rise to an effective temperature-dependent field. This effective field vanishes at the first-order phase transition, whose latent heat is associated with the discontinuity in the order parameter.We use Kikuchi's approximation with the inclusion of triangle bond correlations, and pair and site probabilities in the expression for free energy. We assume that the lipid chains only interact through nearest neighbour pair potentials and that triangle correlations are important for approximate counting of allowed states. Two long-range order parameters and a short-range order parameter are introduced in the formulation of the theory. Both long-range order parameters are discontinuous at the transition temperature. Numerical results for the physical quantities are presented and discussed with respect to earlier work.
A study of the occurrence of dynamically unstable conditions in the middle atmosphere
Authors: Hamilton Kevin
Published: April 2011

There has recently been a great deal of interest in the possibility that vertically propagating internal gravity waves may be dissipated by small-scale convective or shear instabilities in the upper stratosphere and mesosphere. In the present study, a very simple analysis of about 3000 rocket soundings of temperature and wind at several stations between 8°N and 59°N was conducted in order to obtain quantitative estimates of the frequency of occurrence of dynamically unstable conditions as a function of height, latitude, and season. It was found that in about one-third of the profiles, the local Richardson number dropped below 0.25 at some level near the stratopause. From the results, it appears that gravity wave "breaking" generally occurs at considerably higher altitudes in the tropics than in midlatitudes. There is also a fairly clear indication of higher wave breaking levels in summer than in winter, at least at high latitudes.
A vibrational and rotational analysis of the band system of HDCO
Authors: Clouthier D. J. , Craig A. M. , Birss F. W.
Published: April 2011

The vibronic bands of the [Formula: see text] system of HDCO have been identified by magnetic rotation and absorption spectroscopy. Rotational analyses have been carried out for four bands. The excited state geometry and a Coriolis perturbation in the 210 band are discussed.
Cylindrical magnetosonic shocks in a collisional plasma
Authors: Sarma S. N. , Bujarbarua S.
Published: April 2011

We have investigated the nonlinear propagation of magnetosonic waves in a cylindrical plasma column. Taking into account the finite resistivity, thermal conductivity, and the generalized Ohm's law, it has been shown that such a propagation is governed by a modified Korteweg–DeVries–Burgers equation. The early time shock like solution of this equation is obtained and discussed.
A numerical method for diffusion, attachment, and recombination coefficients in uv ionized gases
Authors: Shammas S. , Seguin H. J. J.
Published: April 2011

A numerical technique is established for analyzing the experimental data from photoplasma density measurements. The simultaneous effects and relative importance of photo-ionization, diffusion, attachment, and recombination are considered for a typical laser media. The results suggest that the initial diffusion of electrons plays an important role in uv preionized CO2 laser systems. The effects of gas mixture and pressure on the generation and penetration of uv radiation for a spark source is also determined.
Gas ionization by focused laser beams
Authors: Brito A. L. de
Published: April 2011

It is shown that the effect of line broadening by focusing may contribute considerably to the observed laser-induced ionization of gases even when the ionization energy of the gas molecules is well above the mean photon energy of the laser radiation.
Observables in
Authors: Rustgi M. L. , Nunemaker R. D. , Vyas R.
Published: April 2011

A summary of the results obtained by the authors on the cross section, polarization, and asymmetry function for [Formula: see text] at medium and low gamma-ray energies is presented. The results on the disintegration of the oriented deuterons by unpolarized gamma rays illustrate the differences arising in two of the observables from the use of two different nucleon–nucleon potentials.
Photonuclear reactions in few-body systems: recent results, current program, and future plans at the Massachusetts Institute of Technology Bates Laboratory
Authors: Matthews J. L.
Published: April 2011

An outline is presented of the ongoing research on photonuclear reactions in few-body systems at the Bates 750-MeV electron accelerator laboratory.
A measurement of the neutron–proton capture differential cross section at extreme centre-of-mass angles at En = 61 MeV
Authors: Ninane A. , Dupont C. , Leleux P. , Lipnik P. , Macq P.
Published: April 2011

The differential cross section for neutron–proton capture was measured at extreme centre-of-mass angles for a neutron energy of 61 MeV. The experimental setup is described. The 0° cross section favourably compares with previous experiments.
A neutron scattering study of spin dynamics in the one-dimensional paramagnet CsMnBr3
Authors: Gaulin B. D. , Collins M. F.
Published: April 2011

CsMnBr3 is a quasi-one-dimensional Heisenberg antiferromagnet. We present results of the magnetic inelastic response of CsMnBr3 across the magnetic Brillouin zone by neutron scattering techniques. Well-defined spin-wave modes, characteristic of one-dimensional magnetic insulators, are found over most of the zone in the paramagnetic phase at 15 K. The zone centre response is not sharp, but peaks in the scattering function S(k, ω) are found. No excitation branch going to zero energy at zero wavevector is found. At small wavevectors there is a mode with energy 1.7 ± 0.2 meV and we use it to identify planar anisotropy in this system. The mid-zone response as a function of temperature is analyzed in terms of a generalized Langevin equation approach (Mori formulation) to the dynamics of the one-dimensional Heisenberg antiferromagnet. The theory contains no adjustable parameters. Our results are compared with two truncation schemes of the theory. We report qualitative agreement with the theories, including the observation of upwards renormalization of spin-wave energy with temperature. Quantitative agreement is less than good for either truncation scheme.
Electrodeless breakdown of gas in slightly conducting glass bulbs
Authors: Curzon F. L. , Parfeniuk D. A. , Friedmann D. E.
Published: April 2011

A model is presented that accounts for the effect of conduction currents on the electrodeless breakdown of gas contained in glass bulbs immersed in 60-Hz alternating fields that are either linearly or circularly polarized. It is suggested that photoconductivity of the glass, induced by photons from the breakdown plasmas, significantly affects the dependence of the breakdown frequency on the applied field strength.
Group actions as applied to symmetry breaking in hexagonal crystals with space group P63/m
Authors: Morra Rose M. , Armstrong Robin L.
Published: April 2011

A procedure is outlined that allows one to predict the possible low-symmetry space groups for a commensurate phase transition associated with a broken symmetry. By considering each irreducible representation of the high-symmetry space group and using a subduction procedure involving the theory of group actions, one may determine a complete set of representative order parameters and their little groups. Each little group can be identified as a possible space group for the low-symmetry phase. The method is used to deduce all possible broken symmetries of space group P63/m that can result from a phase transition associated with one of the symmetry points in the Brillouin zone. As a specific application of the resulting tables of possible order parameters and associated low-symmetry space groups, changes in the X nuclear quadrupole resonance spectrum due to structural phase transitions in hexagonal AX3 crystals with the high-symmetry space group P63/m are considered.
Orientational ordering in solid ortho–para H2 mixtures and analogy with a spin glass
Authors: Harris A. Brooks , Meyer Horst
Published: April 2011

A review is presented of our understanding of the orientational ordering in solid hydrogen, where ortho-H2 molecules are subject to anisotropic electric quadrupole–quadrupole interactions. This review pertains to solid H2 at low pressures and is concerned mostly with NMR experiments. After a discussion of the phase transition from the disordered hexagonal close-packed (hep) to the long-range ordered cubic phase, a description is given of experimental investigations of the ordering in the hep phase for ortho concentrations X < 0.53. This ordering appears to take place continuously as the temperature decreases. The question as to whether or not this phase is to be called a quadrupolar glass phase is addressed, and comparison is made with the orientational freezing in other compounds. A theoretical analysis is given to show that the ortho–para mixture is the analog of a spin glass in a random field for which no phase transition is expected.
Diffusion coefficient of a protein in a fluid membrane: numerical calculation
Authors: Wiegel F. W. , Heringa J. R.
Published: April 2011

The drag force on an integral membrane protein is usually calculated with an asymptotic formula by Saffman. We have calculated this force by numerically solving the linearized Navier–Stokes equation. The results show that Saffman's formula is accurate within a few percent relative error for the usual range of parameter values. The mathematical equivalence of diffusion in an inhomogeneous membrane with the effective conduction of an inhomogeneous conductor is used to find a relation for the effective diffusion coefficient of a protein in an inhomogeneous membrane.
Far-infrared absorption in liquid nitrogen: a theoretical study
Authors: Joslin C. G. , Singh S. , Gray C. G.
Published: April 2011

We present a simple theory of the far-infrared collision-induced absorption spectrum of liquid nitrogen. Assuming a quadrupolar induction mechanism, and neglecting the small anisotropy in the N2 intermolecular potential, we represent the spectral profile as the convolution of a single-molecule free-rotation spectrum with an intermolecular translational component. Information theory is used to estimate the least-biased form for the latter, based on our knowledge of its zeroth and second spectral moments (the calculation of M0tr and M2tr is illustrated in the Appendix). In this way we avoid the need to make questionable assumptions about the system dynamics. Our theory contains no adjustable parameters, yet the computed line shapes are in excellent agreement with the available experimental data. Absolute intensities are underestimated by about 40%.
Cooperative fluorescence by three-level atoms in a strong excitation field
Authors: Freedhoff Helen S.
Published: April 2011

When a system of two-level atoms interacts with a very intense field, the phenomena associated with superradiance do not appear in the fluorescent radiation. The question has been raised, "Can pumping by an intense field inhibit the occurrence of superradiance in the fluorescence of a system of three-level atoms to the third (nonresonant) level?" In this paper, we calculate the fluorescence spectrum of 2 three-level atoms. We find that superradiance, while absent in that part of the radiation corresponding to resonance fluoresence, is present in the radiation to the nonresonant level.
A simple eigenvalue formula for the quartic anharmonic oscillator
Authors: Hall Richard L.
Published: April 2011

The eigenvalues Enl(λ) of the Hamiltonian H = −Δ + r2 + λr4 are analysed with the help of "potential envelopes" and "kinetic potentials." The result is the following simple approximate eigenvalue formiula:[Formula: see text]where E ≥ P = (4n + 2l − 1) and Q = 3(An + Bl − C)4/322/3. E is a lower bound to Enl if (A, B, C) = (1, 1/2, 1/4) and a good approximation if (A, B, C) = (1.125, 0.509, 0.218).
Side bands in collective resonance fluorescence
Authors: Zaidi H. R.
Published: April 2011

The fluorescence spectrum of a system of strongly driven atoms, contained in a region that is small compared with the wavelength, is calculated using a screened interaction model. Coulomb dipole–dipole interaction is neglected, but a Markov approximation is not made. The side bands at ω′ = ω ± Ω and ω ± 2Ω are investigated in detail (ω′(ω) is the emitted photon (pump field) frequency; Ω is the Rabi frequency). The intensity and line width of the side bands at ω ± 2Ω is reduced owing to S breaking in our model. Non-Markovian corrections split the side band at ω ± Ω.
Stable, tough, adherent Langmuir–Blodgett films: Preparation and structure of ordered, true monolayers of a phthalocyanine
Authors: Kovacs G. J. , Vincett P. S. , Sharp J. H.
Published: April 2011

The first clear evidence for the preparation of true Langmuir–Blodgett (LB) monolayers and built-up multilayers of a lightly substituted phthalocyanine (Pc) is reported. It is shown that the LB films are well ordered and thermally and structurally stable, and that the structure is very similar to that of crystals of the unsubstituted Pc. The films are tough, adherent, and ultrathin (~17 Å). Layers of this type may permit the first really practical electronic devices that contain (insulating) LB films.
Inflationary early universe cosmology in a generalized theory of gravitation
Authors: Moffat J. W. , Vincent D.
Published: April 2011

A solution of the field equations of the nonsymmetric theory of gravitation for the early universe starts with a far-from-equilibrium state and generates perturbations whose evolution is consistent with galaxy formation.
Critical anomalies in EPR spectra near the ferroelectric phase transition in tris-sarcosine calcium chloride crystals
Authors: Jerzak S. , Fujimoto M.
Published: April 2011

A comparative EPR study with various paramagnetic probes of iron-group elements has been carried out on the ferroelectric phase transition in tris-sarcosine calcium chloride (TSCC) crystals. These ions have yielded complementary results, and one probe was found to be insufficient to obtain necessary information about the transition mechanism. While the soft-mode vector is inferred from the VO++ spectra, either Cr+++ or Fe+++ ions are best suited to observe the critical phenomena near the transition temperature (Tc ~ 130 K). A critical broadening above Tc and an asymmetrical splitting below Tc are observed in the Cr+++ and Fe+++ spectra. The Mn++ spectra are unique in that the order–parameter fluctuation appears only slightly in the line widths above Tc, while the critical region below Tc is characterized by the coexistence of para- and ferroelectric phases. The critical slowing-down effect in the EPR line widths is found to be consistent with that observed in dielectric measurements, suggesting that sarcosine dipoles in TSCC crystals are associated with the elementary dipole for spontaneous polarization.
Detection of copper precipitates in Cu2O by NMR
Authors: Hughes D. G. , Mohanty S. , Pandey L. , Weichman F. L.
Published: April 2011

Weak 63Cu NMR signals characteristic of metallic copper have been found in three type-C Cu2O crystals, but not in types A and B. This is in accordance with presently accepted models of these materials. The resonances are asymmetric in two of the three crystals. One shows skin-depth effects, implying particle sizes [Formula: see text], the other shows some second-order quadrupole broadening, presumably associated with strains or surface effects. From the areas under the absorption curves, mass concentrations of copper precipitates ranging from 0.023 to 0.034% are deduced. However, the smallest value is found from an asymmetric resonance where significant loss of signal must have occurred. The data are not inconsistent with a concentration of about 0.034% for all three crystals. For type-A and -B material, an upper limit of 3–7 ppm can be placed on the concentration, depending on the assumed contribution of the satellites to the resonance. 63Cu resonances associated with the transitions between Zeeman-split ± 1/2 quadrupole states in Cu2O were troublesome, since they overlapped the metal resonance at many sample orientations. Strong Cu2O signals, observed at one orientation, indicated that part of the crystal must have grown with {111} faces.
Dipole oscillator strength distributions and properties for SO2, CS2, and OCS
Authors: Kumar Ashok , Meath William J.
Published: April 2011

Dipole oscillator strength distributions have been constructed and used to evaluate integrated oscillator strengths, and a variety of dipole oscillator strength properties, for ground state SO2, CS2, and OCS. Each distribution has been constructed by using experimental and theoretical photoabsorption cross sections and by subjecting the resulting dipole oscillator strength data to constraints provided by the Thomas–Reiche–Kuhn sum rule and molar refractivity data for the relevant dilute gases. The discussion includes graphical presentations of how various spectral regions of the dipole oscillator strength distributions contribute to the more important dipole properties.
On the effective Lagrangian for scalar electrodynamics
Authors: Chowdhury Abul Mansur , McKeon Gerry
Published: April 2011

The one-loop effective Lagrangian in scalar electrodynamics is computed using an expansion to second order in the external electromagnetic field and a WKB-type approximation. Quantum fluctuations of both the scalar and vector fields about background scalar and electromagnetic fields are considered.
Wave–particle interaction and enhanced precipitation of charged particles
Authors: Singh R. N. , Prasad R.
Published: April 2011

In addition to parallel electric fields, the distortions in the geomagnetic field have been considered in the study of resonant whistler wave interaction with gyrating charged particles. Mead axisymmetric distortions in the geomagnetic field have been considered and new expressions for the inhomogeneity parameter, αd, have been obtained. Considering the diffusion of charged particles in pitch angle, the variation in the precipitating electron flux under varying magnetospheric conditions has been computed. The variation in the distribution of trapped charged particles is shown to play an important role in controlling the electron flux precipitated into the lower ionosphere.
Diffraction of a plane electromagnetic wave by a parallel plate grating with dielectric loading: the case of transverse magnetic incidence
Authors: Kobayashi Kazuya
Published: April 2011

Wave scattering and diffraction problems concerning objects with complex cross sections have been widely investigated so far with the advance of electronic computers. In this paper, a periodically placed parallel plate grating with dielectric loading is considered, and the problem of diffraction of a TM polarized plane wave is analyzed with the aid of the Wiener–Hopf technique. Introducing the Fourier transform pair for the unknown scattered field and applying boundary conditions in the transform domain, one can formulate this problem as the single Wiener–Hopf equation. This functional equation is then solved by a decomposition procedure and a rigorous solution is obtained. Furthermore, approximate solutions are derived by applying the modified residue calculus technique. Based on the above analysis, several numerical examples are given and the characteristics of this grating are discussed.
Rapidity distributions and rapidity–gap correlations in multiparticle production at 50 and 400 GeV/c
Authors: Ahmad S. , Ahrar H. , Zafar M. , Shafi M.
Published: April 2011

Results on the single particle rapidity distributions and rapidity–gap correlations among hadrons produced in 50 GeV/c π−-meson and 400 GeV/c proton collisions with emulsion nuclei have been investigated. Study of the rapidity distributions reveals that the projectile fragmentation is mass independent and the target fragmentation depends upon the target mass. From the rapidity–gap distributions, we find evidence for short-range correlations that indicate that the secondary particles are produced via cluster formations and each cluster should consist of at least three charged particles.
Coulomb excitation of 133Cs with protons
Authors: Singh K. P. , Tayal D. C. , Arora B. K. , Cheema T. S. , Hans H. S.
Published: April 2011

Protons of energy 3.2–4.2 MeV have been used to Coulomb excite the states in 133Cs. The thick-target gamma-ray yields and the angular distributions were measured using a 50 cm3 Ge(Li) detector. The measurements were used to extract the reduced transition probabilities, B (E2) and B(M1), and multipole mixing ratios (δ) for the various transitions. A spin assignment has been made to the 871.8 keV level on the basis of angular distribution data. The results obtained have been compared with those of other authors.
Electric field gradient for nontransitional dilute alloys of aluminium
Authors: Raj S. D. , Prakash S. , Singh J.
Published: April 2011

The electric field gradient (q) and asymmetry parameter (η) are calculated for nontransitional dilute alloys of Al. The nonlocal model potential is used to evaluate the valence-effect contribution and the elastic continuum model is adopted to evaluate the size-effect contribution. Although the nonlocality of the model potential greatly modifies the valence-effect contribution, the valence effect alone does not explain the observed values of q and η. The size-effect contribution is found to be larger than the valence-effect contribution. The calculated and experimental values of q and η are found to be in close agreement for almost all the alloys, and these are found to be correlated to the magnitudes of effective charges on impurities. A comparison of q and η for Cu and Al alloys is also presented.
Thermoluminescence, fluorescence, and optical absorption studies on single crystals of rubidium iodide doped with Eu2+
Authors: Tan K. L. , Sapru S. , Sastry S. B. S.
Published: April 2011

Thermoluminescence, optical absorption, and fluorescence studies on the RbI:Eu2+ system indicate that the Eu2+ ions act as donors on irradiation and thereby convert to the Eu3+ ions. On thermal and (or) optical treatment the electrons released are captured back. The integrated light intensity of the system is an order of magnitude higher than that of the undoped samples. Fluorescence measurements show an emission around 2.83 eV. Thermoluminescence emission spectra give two emission bands peaking around 2.48 and 2.83 eV. A tentative energy band diagram is suggested explaining these emissions. Excitation of irradiated samples with F light is used to support this model.
Characteristics of clusters produced in particle–nucleus interactions at 24, 50, and 400 GeV
Authors: Khushnood H. , Shakeel A. , Irfan M. , Shafi M.
Published: April 2011

Some useful and interesting characteristics of clusters produced in 24 and 400 GeV p–nucleus and 50 GeV π−–nucleus interactions have been investigated. The maximum number of charged shower pions constituting a cluster is three at 24 GeV, whereas at 50 GeV and beyond, this number is observed to be four. Further, the results reveal that the cluster size is independent of the star size, nature, and energy of the incident hadron beyond 50 GeV projectile energy. This observation is in accord with the "big hadron" approach suggested for explaining multiparticle production where the centre of the nucleus is visualized to behave like a "big hadron" and the interaction is envisaged to proceed via hadron – "big hadron" collisions.
Electron attachment to amides studied by low-pressure chemical ionization and electron swarms: comparison of the gas and liquid phase
Authors: Tran-Thi T. H. , Koulkès-Pujo A. M.
Published: April 2011

The low-pressure chemical ionization and electron swarm techniques were used to determine the density effect of the environment in the case of electron attachment to four linear or cyclic, primary or substituted amides: N-methylacetamide, dimethylacetamide, pyrrolidone, and N-methylpyrrolidone. The results are compared with those obtained previously for the same compounds in polar liquid phases, where they have been used either as solutes or as solvating media. From this comparison, the electron attachment scheme proposed for the dense gas phase was extended to the liquid phase.
Ondes electromagnétiques de surface en géométrie cylindrique. Les modes de révolution d'ordre supérieur
Authors: Zepp G. , Wick A. , Ritoux G. , Fabre G. , Billaud M.
Published: April 2011

We have studied the revolution electromagnetic surface wave modes of high order (TM, TE) propagating at the surface of a circular cross-sectional metallic cylinder coated with two dielectrics. We have determined precise analytical expressions of attenuation factor and power localization ratio.
On different formulas for the Tc of an impure anisotropic superconductor
Authors: Ashraf M. , Carbotte J. P.
Published: April 2011

Exact numerical solutions of the Eliashberg equations are obtained for several representative metals, from which the impurity dependence of the critical temperature of an anisotropic superconductor is determined. The exact results are used to assess the accuracy of some of the simple, approximate, but analytic, formulas now available in the literature. All are found to be, at best, semiquantitative. An attempt is made to improve on the available formulas by deriving a new one based on the original quantitative work of Leavens and Carbotte for pure metals. While our final analytic formula should be useful for many purposes, it is still found that for accurate quantitative work the full equations are preferable.
Induced rototranslational absorption spectra of the D2–Ar–He mixture
Authors: Barnabei M. , Buontempo U. , Codastefano P. , Maselli P.
Published: April 2011

The rototranslational absorption spectrum of the D2–Ar–He mixture at 165 K has been measured at different helium concentrations. By subtracting the Ar–He and D2–He contributions from the D2–Ar–He spectrum it is possible to derive the spectrum due to the D2–Ar pairs only. The density effects on the pair spectrum are compared with those previously observed in D2–Ar spectra.
Statistical mechanics of quantum one-dimensional damped harmonic oscillator
Authors: Borges E. N. M. , Borges O. N. , Ribeiro L. A. Amarante
Published: April 2011

We calculate the thermal correlation functions of the one-dimensional damped harmonic oscillator in contact with a reservoir, in an exact form by applying Green's function method. In this way the thermal fluctuations are incorporated in the Caldirola–Kanai Hamiltonian.