bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and Magnetism in the Layered CMR Manganites La2-2xSr1+2xMn2O7 (x= 0·3, 0·4)
Authors: Argyriou D. N. , Mitchell J. F. , Jorgensen J. D. , Goodenough J. B. , Radaelli P. G. , Cox D. E. , Bordallo H. N.
Published: June 2013

In this paper we describe a detailed neutron diffraction investigation of the
crystal and magnetic structure of two layered CMR manganites
La1·2Sr1·8Mn2O7
(x = 0·4) and
La1·4Sr1·6Mn2O7
(x = 0·3). In these materials of reduced
dimensionality compared to the 3D perovskites, we find competing effects
between charge-lattice and spin degrees of freedom. These effects can be
investigated by studying the behaviour of crystal and magnetic structure as a
function of temperature, composition and hydrostatic pressure. We find
opposite lattice responses to the onset of charge delocalisation and magnetic
ordering in these two layered compounds. Below the insulator-to-metal
transition (TIM), the lattice response suggests that charge is transferred to
d3z2-r2
orbitals in
La1·2Sr1·8Mn2O7
and to
dx2-y2
orbitals in
La1·4Sr1·6Mn2O7.
We argue that these changes are too large to be due to chemical differences.
Instead we suggest that the orbital configuration of the Mn ion below TIM is
sensitive to electronic doping. In
La1·2Sr1·8Mn2O7
we find that the lattice response at TIM to be driven by lattice displacements
that relax below TIM, consistent with polaronic degrees of freedom. We also
note that the competition between super- and double-exchange to be significant
in reduced dimensions. This is manifested in the change in the sign of the
apical Mn-O bond compressibilities above and below TIM. Finally, we describe
the magnetic structure of these two different layered manganites. We find that
electronic doping also results in significant changes to the ordered
arrangement of Mn spins. Interestingly the magnetism in reduced dimensions in
these materials can be varied from relative simple structures that show
ferromagnetic inter-bilayer coupling as observed in
La1·2Sr1·8Mn2O7
to structures with antiferromagnetic inter-bilayer coupling as found in
La1·4Sr1·6Mn2O7.
Estimation of the Properties of Quarks. I. Vector Quark?Quark Interaction
Authors: Smith GB , Tassie LJ
Published: June 2013

From the sum rules for hadron scattering, the nucleon form factors, and the masses of the hadrons, the properties of quarks are estimated as: 2 Ge V Jc2 ;:; quark mass ;:; 30 Ge V Jc2, 0�1 fm ;:; range of the quark-quark interaction ;:; 0�25 fm. The hadrons are described by a relativistic independent quark model using the Dirac equation with a potential energy term for the effective interaction.
Estimation of the Properties of Quarks. II. Scalar Quark?Quark Interaction
Authors: Smith GB
Published: June 2013

Describing the hadrons by a relativistic independent quark model, using the Dirac equation with a scalar potential for the effective interaction, the range of the quark-quark interaction is found to lie between O� 3 and 0�4 fm. The hadronic spectrum is shown to be independent of the quark mass and the form of the quark-quark interaction.
On the Calculation of Neutron Tunnelling Cross Sections
Authors: May RM , Nicholls IR
Published: June 2013

We present an accurate expression for the matrix element for neutron tunnelling reactions using Hulthen wavefunctions for both initial and final neutron states and a Hulthen form for the neutron-binding potential (previous work is confined to asymptotic neutron wavefunctions and zero-range potentials).
Dislocation Dipoles in Elastically Anisotropic Crystals
Authors: Forwood CT , Humble P
Published: June 2013

The major features of the images of dislocation dipoles obtained by two-beam electron microscopy which enable dipoles to be identified and distinguished from other defects are discussed. The positions of stable equilibrium of dipoles in various f.c.c. and b.c.c. materials have been derived using linear anisotropic elasticity.
18 cm Observations of Galactic OH from Longitudes 128° to 300°
Authors: Manchester RN , Robinson BJ , Goss WM
Published: June 2013

Observations have been made of 18 cm OR emission and/or absorption for 12 sources between galactic longitudes 128� and 300�. The OR is seen in emission in five of the sources, and the four Stokes parameters of the emission profiles have been measured. A new type of strong wideband OR emission has been found near III = 284�. There are two sources where weak emission at 1612 MHz accompanies absorption on the other three lines.
Quasi-Stellar Objects in the Parkes 2700 MHz Survey: The Selected Regions and the ±4° Declination Zone
Authors: Bolton JG , Wall JV
Published: June 2013

One hundred and thirty�two quasi�stellar objects or possible quasi.stellar objeots have been found in the first areas of the Parkes 2700 MHz survey. Identifi� oations for 36 of these have a.1ready been published and 67 have been oonfirmed by spectrosoopy or two�oolour photography. Relationships between the various radio and optioa.l pa.ra.meters are briefly disoussed.
A Multilevel Formalism for Neutron Elastic Scattering Cross Sections
Authors: Clayton E
Published: June 2013

An extension of the Feshbach, Porter, and Weisskopf formalism has been developed for neutron elastic scattering. The emphasis in this paper is on resonanceresonance interference and explicit use of the background R matrix. The results of this formulation are compared with experimental data in the resonance region for the nuclides 238U, 197Au, and 23Na.
A Dynamic Model of the Slater K.D.P. Ferroelectric
Authors: Irvine RD
Published: June 2013

Several dynamical models of the Slater K.D.P. model of a ferroelectric are studied and, following Glauber, master equations are derived for the time development of these models. A computer simulation of the models is used to study the solutions to these equations, and to compare the equilibrium results with Lieb's exact solution of the equilibrium case. Excellent agreement is obtained in one case.
Monte Carlo Investigations of Non-Equilibrium Effects at High Values of E/p in Swarm Experiments in Hydrogen
Authors: Folkard MA , Haydon SC
Published: June 2013

The results of a Monte Carlo computer simulation of the properties of electrons in a gas at pressure p sUbjected to a constant electric field E are presented for E /p = 350 V cm -1 torr-1 in hydrogen. Evidence is provided that the spatial growth of ionization is essentially non-equilibrium in these circumstances and that the general form of the predicted growth of currents is consistent with experiment.
Disturbance Daily Variation During the IGY
Authors: Petersons HF
Published: June 2013

The disturbance daily variation field SD, was studied for the three seasons using lGY data from 50 observatories. Equivalent external and internal electric current systems which could account for the SD field were obtained by the method of spherical harmonic analysis. The external current systems were found to be only approximately symmetrical about the geomagnetic equator
Short Communications Temperature Profiles in Some Heat Conduction Problems with Spherical Symmetry
Authors: Brown A , Downes GL
Published: June 2013

Temperature profiles are known for several composite systems involving a sphere losing heat into an infinite surrounding medium. Lovering (1935, 1936) considered the diffusion of heat from a sphere into a cooler medium with the same thermal properties, i.e. the same conductivity K and diffusivity k. The initial temperatures of the two bodies were assumed constant.
Computation of Geomagnetic L Coordinates
Authors: Schaeffer RC
Published: June 2013

The study of the distribution of geomagnetically trapped charged particles is aided by the introduction of a parameter L which is a function of the magnitude of the magnetic field and an integral invariant of the particle motion evaluated between the mirror points of the particle trajectory, which are referred to here as absolute conjugate points of the field (McIlwain 1961).
Quantization of Lagrangians for Charges in an External Field
Authors: Hayes CF , Craig CD
Published: June 2013

Generally Lagrangians in classical mechanics depend on the coordinates and velocities of the particles at one instant of time. Obviously such an approach assumes that all interactions are instantaneous, and hence that the field has an infinite velocity
keV Resonance Neutron Capture in Iron
Authors: Kenny MJ
Published: June 2013

Resonance behaviour has been observed at a number of neutron energies between 5 and 90 keY. Transition intensities show strong fluctuations with neutron energy. The presence of p- and/or d-wave capture is inferred from the occurrence of transitions to high spin states. A distribution of reduced widths for low spin states suggests some departure from statistical processes, particularly for the strongest transitions.
Inelastic Collisions in the Townsend?Huxley Diffusion Experiment
Authors: Francey JLA , Stewart PK
Published: June 2013

The Boltzmann equation, including density gradients, is solved for the electron distribution function in the Townsend-Huxley experiment. Elastic and inelastic collisions with constant cross sections are assumed to occur, the inelastic energy loss per collision being small compared with the mean energy. The inelastic energy loss and the electron mean energy are calculated and tabulated over a range of values of EIP.
Some Identifications for Weak Sources in the Parkes Catalogue for Declinations +20° to ?20°
Authors: Bolton JG , Wall JV , Shimmins AJ
Published: June 2013

Accurate positions and flux densities at 2700 MHz have been measured for 156 weak sources in the Parkes catalogue for declinations 0� to +20� and 0� to -20�. Identifications are suggested for 22 of the sources, 6 with galaxies and 16 with possible quasi. stellar objects.
The Effects of Cylindrical Geometry on Normal Ionizing Shock Waves
Authors: Blackburn TR , Brennan MH
Published: June 2013

Most of the theoretical work on the characteristics of normal ionizing shock waves, as exemplified by the work of Taussig (1967), has been restricted to a onedimensional model. Only Woods (1965) has attempted to include the effects of cylindrical geometry. However, the complexity of the problem in cylindrical geometry forced Woods to ignore the radial dependence of the azimuthal drive field bo? which he took to be given by the relation (his equation (3�
The Parkes 2700 MHz Survey. Catalogue for 03h, 11h, 19h, and 23h Zone, Declinations ?33° to ?75°
Authors: Shimmins AJ
Published: June 2013

A catalogue of 618 extragalactic radio sources obtained from a sky survey at 2700 MHz is presented. The area of 0�42 sr covers four southern zones of R.A. 03h to 04h , II h to 12h , 19h to 20h , and 23h to 00h, between Dec. -330 and -75�, with a region omitted in the llh zone which is close to the galactic plane. The catalogue is complete to a limiting flux density of 0�32 f.u. at 2700 MHz and is thought to be 90% complete at a flux density of 0�20 f.u. The positions are accurate to 15" arc or slightly better in both coordinates for sources stronger than 0�32 f.u.; the flux densities of the weaker sources are accurate to 0�02 f.u., and for sources stronger than 1 f.u. the accuracy is 3%.
Capture of 10?100 keV Neutrons in Isotopes of Titanium
Authors: Broomhall GJ
Published: June 2013

Gamma ray spectra are presented as functions of neutron energy for capture of 10?100 keV neutrons in natural titanium. The spectra are dominated by transitions to the first, third, and fifth excited states of 49Ti which show strong fluctuations with neutron energy. The nature of these fluctuations and their relation to the nature of the capture process is discussed. A small but measurable strength in the transition to the 7/2? ground state of 49Ti has been observed and this is interpreted as evidence for the existence of a d-wave resonance in the reaction 48Ti(n, ?)49Ti at 39 keV. Transitions at 8260 and 8380 keV are assigned to capture in 47Ti.
The Effect of a Temperature Gradient in a Single Crystal on E.P.R. Line Shape and Width
Authors: Ja YH
Published: June 2013

Temperature is an important parameter in electron paramagnetic resonance experiments and studies at different temperatures can give a great deal of useful information about the investigated spin system and its interaction with its environment. Generally speaking, all of the parameters in the spin-Hamiltonian, such as the g factor, hyperfine interaction constants, etc., are independent of the temperature to a first-order approximation, but the line shape, line width, and spin-lattice relaxation time are quite sensitive to temperature changes. However, e.p.r. studies in many natural or synthetic crystals with very low concentrations of paramagnetic impurity-ions indicate that the line width ?H and the line shape are virtually independent of the temperature T (provided T is not too low), while the crystal-field parameters in the spin-Hamiltonian, such as D and E, show a considerable variation with temperature. The former comes about because the line widths in such cases depend mainly on the mosaic structure (Shaltiel and Low 1961; Wenzel and Kim 1965) and the local distortions (mechanical or electrical strains) (Wenzel and Kim 1965) of the crystal lattice which are practically independent of the temperature. The latter is mainly due to the shrinkage or expansion of the crystal which changes the interactions between the paramagnetic ion and its neighbouring ions.
Solutions of the Relativistic Two-Body Problem. I. Classical Mechanics
Authors: Cook JL
Published: June 2013

The chief difficulty of lack of simultaneity of events in all Lorentz frames in relativistic mechanics is overcome using a proper time calibration method. The electromagnetic and gravitational point source interactions are derived. A Lagrangian and Hamiltonian formalism is shown to be valid. The mechanics can be quantized easily. Relativistic corrections are applied to the problem of planetary motion, a model for the relativistic Coulomb interaction is explored, and the relativistic harmonic oscillator is evaluated.
Reaction Matrix Approach to the Inverse Problem
Authors: Cook JL
Published: June 2013

The problem of inverting the calculation of cross sections to one of determining interaction potentials from cross sections is dealt with using the reaction matrix approach. The experimentally obtained resonance parameters are utilized to calculate constants which are coefficients of expansion of the potential in terms of known functions.
Time Direction of Information Propagation and Cosmology
Authors: Pegg DT
Published: June 2013

In conventional electrodynamic theory, the advanced potential solution of Maxwell's equations is discarded on the ad hoc basis that information can be received from the past only and not from the future. This difficulty is overcome by the Wheeler?Feynman absorber theory, but unfortunately the existence of a completely retarded solution in this theory requires a steady-state universe. In the present paper conventional electrodynamics is used to obtain a condition which, if satisfied, allows information to be received from the past only, and ensures that the retarded potential is the only consistent solution. The condition is that a function Ua of the future structure of the universe is infinite, while the corresponding function Ur of the past structure is finite. Of the currently acceptable cosmological models, only the steady-state, the open big-bang, and the Eddington-Lema�tre models satisfy this condition. In these models there is no need for an ad hoc reason for the preclusion of advanced potentials.
A Note on the Adler?Adler Resonance Formalism
Authors: Cook JL
Published: June 2013

Over restricted energy ranges, the Adler?Adler method. of parameterizing resonance cross sections is in general the exact result of inverting the channel matrix. This provides a simple analytical form for the cross section which can be used in reactor physics calculations.
A Method for Inverting the Channel Matrix in R-Matrix Theory
Authors: Bertram WK
Published: June 2013

A technique is presented for inverting the channel matrix which occurs in R-matrix theory. The collision matrix is expressed in a form which does not involve matrix inversions; it is evaluated by the application of a recurrence relation. The connection between this method and the level matrix formalism is examined.
Larmor Radius and Collisional Effects on the Dynamic Stability of a Composite Medium
Authors: Bhatia PK , Steiner JM
Published: June 2013

The combined effects of a finite ion Larmor radius and collisions with neutral atoms on the dynamic stability of a composite medium are investigated. The stability analysis has been carried out for a semi-infinite composite medium of variable density in the presence and absence of a uniform streaming motion. Wave propagations transverse to the direction of the uniform horizontal magnetic field have been considered. It is found that the effects of the collisions as well as the finite ion Larmor radius are stabilizing on both streaming and non-streaming composite media.
Propagation of Electromagnetic Waves in a Weakly Ionized Warm Magneto-plasma
Authors: Misra SP , Shukla PK , Misra KD
Published: June 2013

Modified wave equations for a weakly ionized warm magnetoplasma are obtained by linearizing Maxwell's equations with the help of the equation of state and the conservation equations for mass, momentum, and energy. The expressions derived for the refractive index for oblique and normal wave propagation from solutions of the equation of motion and from the modified wave equations are found to be equivalent. The results are used to study wave propagation in the ionosphere and the magnetosphere.
Polarized Radio Emission from Five Supernova Remnants
Authors: Milne DK
Published: June 2013

Maps are presented of the polarization and total power emission at 2700 MHz from five southern supernova remnants: MSH09?32, 10?53, 14?63, 15?52, and 15?56. Observations of 14?63 and 15?06 at 1410 MHz are also presented.
The Effect of Clustering on the Measurement of the Mobility of Potassium Ions in Nitrogen Gas
Authors: McDaniel EW
Published: June 2013

McDaniel and Martin (1971) have suggested that the zero-field reduced mobility of (unclustered) K+ ions in nitrogen at room temperature and low pressures (~ 0�1 torr) is accurately enough known to be useful in pressure calibration of drift tubes and other types of apparatus employed in atomic collision experiments, where the uncertainty in the value of the gas pressure frequently represents the largest source of error in the measurements. Elford (1971) has questioned the validity of this suggestion on the grounds that he has observed a very slight, explicit dependence of the reduced mobility of K+ ions on the gas pressure in drift tube experiments with nitrogen and other gases. Although this pressure effect cannot be reconciled with existing mobility theory (McDaniel and Mason 1972), Elford believes the effect to be real and hence maintains that in fact the true mobility of unclustered K+ ions in nitrogen is not accurately known. The purpose of this communication is to point out that Elford's experiments with nitrogen were conducted at pressures sufficiently high that significant clustering of nitrogen molecules with his K+ ions inevitably occurred and that consequently the suggestion of McDaniel and Martin (1971) is not weakened by his findings.
Numerical Study of a Model Three-Body System
Authors: Dodd LR
Published: June 2013

An investigation is made of the properties of a simple three-body system consisting of three particles moving in one dimension and interacting through d-function potentials. The exact equations of three-particle scattering theory for this system are reduced without approximation to a set of three coupled one-dimensional integral equations which are solved numerically for a wide range of different potential strengths and particle masses. For the special case of identical particles the numerical solutions are compared with the exact solutions found previously by the author. The method of solution for general values of the parameters, which is based on computing the eigenvalue trajectories of the kernel of the scattering equations, allows a. systematic search for three-body bound states. In the case of nuclear or atomic-like configurations, a unique symmetric bound state is found and its binding energy computed. For molecular configurations, where there are two identical heavy particles interacting by the exchange of a third light particle, several excited states of both positive and negative parity are found and a comparison is made of their binding energies with the predictions of the adiabatic approximation. A reaction matrix formulation of the exact equations is used to calculate the probabilities of elastic and rearrangement scattering below the threshold for breakup. When the particles are identical, there is no elastic or rearrangement scattering in the backward direction. However, for particles of different mass or potentials of unequal strength, all kinematically possible scattering processes occur and the scattering properties of the model are quite complex. In particular an interesting feature of the calculations is the appearance of cusps in the elastic cross sections at the rearrangement threshold.
Observations of the Radio Source PKS 0123?01 at 5000, 408, and 80 MHz
Authors: Schilizzi RT , Lockhart IA , Wall JV
Published: June 2013

Observations of PKS 0123?01 (3C 40) have been made at 5000, 408, and 80 MHz with telescopes of comparable beamwidth. The value of the spectral index for the frequency intervals 5000?408 and 408?80 MHz has been calculated for a grid of points covering the source spaced at approximately half-beamwidth intervals. For both frequency intervals the spectrum of emission is found to be significantly steeper for the regions of the source furthest from the associated galaxies NGC 545?547 than for the regions nearest the galaxies. Some implications of this result are discussed. The age and energy requirements of the source have also been estimated.
Calculations with Reaction Matrices in the p?f Shell
Authors: Comins HN , Hewitt RGL
Published: June 2013

Elements of the shell-model reaction matrix have been calculated for the p-f shell with an exact treatment of the Pauli operator. These elements have been used in straightforward calculations of the energy levels of 42Ca and 42Sc and the binding energy of 40Ca.
Oscillatory Convection in a Viscoelastic Fluid Layer in Hydromagnetics
Authors: Bhatia PK , Steiner JM
Published: June 2013

A study is made of the overstable mode of convection in an infinite horizontal layer of a viscoelastic fluid, heated from below, in the presence of a magnetic field. It is shown first that the problem is characterized by a variational principle. Proper solutions are then obtained for the case of two rigid boundaries using the variational method. It is found that the magnetic field has a stabilizing effect on the thermally induced overstability in a viscoelastic fluid, as in the case of an ordinary viscous fluid. The thermodynamic significance of the variational principle is also considered.
On Gravitational Aberrations in Stellar Images
Authors: Cook MW
Published: June 2013

On the basis of a cosmological model which is fundamentally of the Friedmann expanding type with a spherically symmetric inhomogeneity superimposed, a study is made of three gravitational aberrations of purely relativistic origin observed in the images of stellar objects: (1) the "gravitational lens" effect, (2) a dispersion effect whereby a point source would produce a diffuse image, and (3) an 'apparent systematic motion of all light sources towards (or away from) the inhomogeneity. Admissable inhomogeneities in the model must satisfy PU ? 2�104 Mpc, where P is the ratio of the average density of matter within the inhomogeneity to the average density of the universe and U is its diameter in megaparsecs. The assumption is also made that the paths of light rays are described by the null-geodesic equations of the space-time under consideration.
A Discussion of Laser Conditions and the Use of Polarized Nuclei in Grasers
Authors: Hora H , Wilson GVH , George EP
Published: June 2013

A high frequency limitation is derived for y-ray lasers (grasers) from the conditions for the laser threshold. At low temperatures, the use of polarized nuclei should facilitate the roduction and observation of graser action using 'Q switching' by magnetic rotation of the polarization axis.
Ohmic Heating and Ionization Measurements for an Axial Discharge in Hydrogen
Authors: Cross RC , Blackwell BD
Published: June 2013

Experimental results are presented on the heating effect and rate of ionization produced by an axial discharge (~1O kA) in hydrogen gas at filling pressures of 25--400 mTorr. The electron temperature remains very low (about 1�5 eV) even at ohmic heating power levels as high as 200 MWm-3 ? The results are compared with a theoretical model which assumes that the only energy loss mechanism is ionization of neutral particles. The importance of other loss mechanisms, including convection, conduction and radiation, is also discussed.
The Equilibrium Statistical Mechanics of a One-dimensional Self-gravitational System
Authors: Monaghan JJ
Published: June 2013

The configurational integral and the single-particle and pair distributions for a one-dimensional gravitating system are calculated using approximate methods. The Helmholtz free energy and single-particle distributions are in good agreement with the exact analytical results. The pair distribution is new and shows that, in the Vlasov limit, it is approximately the product of two oneparticle distributions. The method may be easily extended to more general systems.
The Effect of Ionization and Recombination on the Resistivity of a Partially Ionized Plasma in a Magnetic Field
Authors: Mathers CD , Cramer NF
Published: June 2013

The generalized Ohm's law for a partially ionized magnetized plasma composed of ions, electrons and neutral atoms is calculated. The plasma is modelled by a three-fluid treatment, with elastic collisions between all three species, as well as inelastic ionization and recombination collisions being taken into account. Ionization is assumed to be due to electron-atom impacts, and recombination is assumed to be due to three-body electron-electron-atom collisions. The resistivity is calculated, and it is shown that the major effect of ionization and recombination is to reduce the resistivity for currents perpendicular to the magnetic field under typical laboratory conditions. However, this resistivity is still greater than Coulomb resistivity, owing to plasma-neutral gas friction.
The Accuracy of Frequency Standards disseminated by HF Radio Paths through the Ionosphere
Authors: Heron ML , Rose RJ
Published: June 2013

The 12 MHz VNG standard frequency transmitted from Lyndhurst has been phase compared with a local standard at Townsville over a total of 54 days. The Doppler shift introduced by the one ionospheric reflection has a diurnal trend which is predictable from the ionosphere parameters fo F2 and M3000F. The optimum time of day for frequency dissemination using VNG 12 is between 1100 and 1530 h. Faster fluctuations generally obscure the diurnal trend, however, and an accuracy of � 0�1 Hz on the 12 MHz carrier is attainable only by averaging the incoming frequency over a 1 h period. Spectral analysis of the fluctuations in frequency show significant spectral amplitudes down to short periods of about 1 min where the time resolution of the measurements provides a cutoff.
A Lagrangian with Higher Derivatives for Arbitrary Spin Fields
Authors: Jeffery EA
Published: June 2013

A Lagrangian that generalizes the Dirac spin t Lagrangian is given. This contains up to 2jth order derivatives for spin j, but can be readily quantized for free fields. Noether's theorem is generalized and the results are shown to conform with other known quantization procedures for arbitrary spin particles. Use of the higher derivative Lagrangian overcomes some of the difficulties encountered by others in rigorously deriving a covariant Feynman propagator.
Equations for Pulsar Magnetospheres with Particle Inertia
Authors: Burman RR , Mestel L
Published: June 2013

This note deals with steadily rotating nonaxisymmetric pulsar magnetospheres, with the effects of particle inertia fully incorporated. It is pointed out that the equations of motion for the component species of a relativistically streaming nondissipative plasma can be considerably simplified by using the steady-rotation constraint together with a fluxoid conservation law and Endean's Bernoulli-type integral.
An Investigation of the Composition of a Hydrogen Plasma using Magnetoacoustic Oscillations
Authors: Brennan MH , Jessup BL , Jones IR
Published: June 2013

This paper reports on the use of observations of magnetoacoustic oscillations to determine the radial particle density and temperature profiles in a hydrogen plasma. The observations comprise measurements, at a number of frequencies, of the radial variations of the oscillation amplitude and of the total flux in the plasma. The analysis allows the determination of radial profiles of the ion and atom number densities.
Some Algebraic Techniques for obtaining Low-temperature Series Expansions
Authors: Enting IG
Published: June 2013

It is shown that low-temperature series expansions for lattice models in statistical mechanics can be obtained from a consideration of only connected strong subgraphs of the lattice. This general result is used as the basis of a linked-cluster form of the method of partial generating functions and also as the basis for extending the finite lattice method of series expansion to low-temperature series.
A Discussion of Radio Wavelength Radiation Generated by Gyrosynchrotron and Langmuir-wave Processes
Authors: Robinson RD
Published: June 2013

Synchrotron and Langmuir-wave emission processes are compared, with special emphasis being placed on metre wavelength radiation from the solar corona. Numerical calculations are presented which relate to brightness temperature, circular polarization and source structure. It is found that both gyrosynchrotron and Langmuir processes can produce brightness temperatures up to ~ 2-3 GK; larger temperatures require induced Langmuir-wave emission. It is further shown that gyrosynchrotron source positions observed at different frequencies may have a dispersion in height within an inhomogeneous background medium. Although many observations may be explained excIusivelyby. one of the two processes, there are numerous circumstances in which both processes are equally likely.
A 30 MHz Map of the Whole Sky
Authors: Cane HV
Published: June 2013

A 30 MHz map of the whole sky has been produced by combining medium resolution surveys of both hemispheres. The map is useful for studying large-scale galactic features away from the galactic plane.
Propagation Effects on the Polarization of Pulsar Radio Emission
Authors: Melrose DB
Published: June 2013

The properties of the natural wave modes of a pulsar magnetosphere are derived in a simple way by appealing to the 'low-density limit'. The properties are evaluated explicitly for a general version of the cold plasma model which includes relativistic streaming motions, and it is argued that this model is probably adequate for pulsar magnetospheres. The observed circular polarization in pulsar radio emission could arise as a propagation effect; the conditions under which initially linear polarization could be converted into partially circularly polarized radiation are summarized. The observed 'orthogonal modes' of polarization could be due to components in the two natural modes having slightly different ray paths. The angular separation of the two rays is found to be a strong function of frequency (!!(), ~ 4 x 108 ne/ /2), and it is suggested that a study of the frequency dependence of 'orthogonal modes' could provide useful information.
Use of Nuclear Techniques in the Characterization of Chrome Black Solar Absorber Surfaces
Authors: Switkowski ZE , Heggie JCP , Clark GJ , Petty RJ
Published: June 2013

A set of electrodeposited chrome black solar absorbers has been subjected to ion beam analysis in an attempt to determine the concentration depth profiles of the major elemental constituents. Chromium distributions were obtained using the 5 2Cr(p, )i)53Mn nuclear reaction, which is resonant at Ep = 1005�2 ke V. The possibility was investigated of inferring oxygen distributions from the )i-ray lineshapes (measured with a Ge(Li) detector) of the direct capture reaction 160(p, )i)17F. Concentration profiles were also obtained for fluorine and sodium contaminants in some chrome blacks. Complete experimental details are given of the various nuclear techniques used. The results of these measurements are discussed in terms of the microscopic physical features of the selective surfaces and are related to the known photothermal properties of the surfaces.
Theoretical Analysis of Plasmon Dispersion in Simple Metals
Authors: Jewsbury Peter
Published: June 2013

The dielectric response of an electron gas has been investigated with a view to understanding the small momentum behaviour of the plasmon peak in inelastic electron energy loss spectra. It is shown that the lifetime of the plasmon and the width of the incident beam both contribute to the apparent flattening of the plasmon dispersion which has been seen to occur in some metals (magnesium, aluminium, indium) for plasmon wavevectors less than ~O�5 A -1. Expressions, beyond the random phase approximation, are derived for the dispersion coefficients up to fourth order in the plasmon wavevector. Good agreement with experiment is obtained.
On the Functional Form of the Transition Probabilities in the Monte Carlo Method as Used in Statistical Mechanics
Authors: Johnson CHJ
Published: June 2013

The transition probabilities W in the traditional Monte Carlo simulation process used in statistical mechanics are shown to satisfy a linear functional equation. General classes of solution to this equation are presented. A simple one-particle mean-field Ising model of a ferromagnet is used in an analytical comparison of the various possible forms of W.
Kinematic Diffusion of Scalar Quantities in Turbulent Velocity Fields
Authors: Lerche I
Published: June 2013

From Kraichnan's direct interaction approximation the normal mode equations are set up for a scalar quantity diffusing kinematically under a turbulent velocity field which is statistically homogeneous and stationary. It is demonstrated: (i) that the mean scalar field responds only to the symmetric part of the velocity turbulence tensor; (ii) that the Kraichnan equation describing the normal mode behaviour is a singular nonlinear integral equation; (iii) that for velocity turbulence which is switched on and off infinitely rapidly the normal modes of the mean scalar field decay in time at a rate which is always greater than that obtaining in the absence of the turbulent velocity field. The motivation underlying these calculations is the problem of particle transport in turbulent astrophysical situations such as the interstellar medium. In such cases the effective Reynolds number is normally large compared with unity, so that expansion approximations for small Reynolds number are apparently not completely free of error.
Meson Mass Formulae in SU(5)
Authors: Anderson Ronald , Joshi GC
Published: June 2013

We present first-order mass formulae for mesons in broken SU(5) and, using the upsilon mass as input, we estimate the masses of the new JP = 0-, 1- and 2+ mesons. We find that the masses of the 0- states exceed those of the corresponding 1- states for single b quark mesons, and that a rather large IS0 - 3S1 splitting occurs for the upsilon family.
Heavy-ion Elastic Collisions and the Nuclear Surface Diffuseness
Authors: Mohr CBO
Published: June 2013

Taking the magnitude of the elements of the S matrix and the nuclear phases to be of Woods-Saxon form in the variable I with width parameter LI, we find that the form of the scattering amplitude components f+(B) and f-(B) is specified by the parameters LI+ and LI- such that LI is closely the geometric mean of LI+ and LI-. Many angular distributions have been analysed into f+(B) and f-(B) to obtain LI+ and LI- and hence LI, the angular momentum diffuseness, from which the nuclear surface diffuseness is obtained, so reducing an ambiguity in the nuclear potential. The case of light ions incident on heavy ions has also been investigated.
A Cylindrical Pulsar Magnetosphere Model with Particle Inertia
Authors: Burman RR , Mestel L
Published: June 2013

An investigation is made of the equations to a steadily rotating nonaxisymmetric pulsar magnetosphere model, with the effects of particle inertia fully incorporated but with no dissipative forces. As an illustrative example the basic theory is applied to a 'cylindrical pulsar' model, in which quantities do not vary parallel to the rotation axis. It is shown that Endean's Bernoulli-type integral imposes severe constraints on particle motion, indicating that, in a realistic model, dissipation (e.g. by radiation damping) may play an essential role.
Neutron and Proton Capture by 6Li
Authors: Barker FC
Published: June 2013

The 6Li(n, y) and 6Li(p, y) cross sections at low energies are calculated by means of a direct-capture potential model and the results are compared with experimental data. Potential depths chosen to fit 6Li(n, n) and 6Li(n, ex) data are also used for the 6Li + P system. Standard values of the potential parameters and spectroscopic factors give cross sections that are too small for both the (n, y) and (p, y) reactions. However, modified values of these parameters that fit the (n, y) cross section also give good agreement with the (p, y) cross section.
The 7Be(p, ?)8B Cross Section at Low Energies
Authors: Barker FC
Published: June 2013

The nonresonant part of the 7Be(p, )I)8B cross section at low energies is recalculated by means of a direct-capture potential model, using parameter values determined by fitting 7Li(n, n)7Li and 7Li(n, )I)8Li data. Standard values of the potential parameters and spectroscopic factors give values of the 7Li(n,)I) cross section that are too large. Modified values that fit the thermal-neutron capture cross section predict 7Be(p,)I) cross sections that are much less than the experimental values. Also, shell model calculations predict resonant 7Be(p,)I) cross sections that are smaller than the experimental values. It is suggested that the accepted experimental values of the 7Be(p, )I) cross section may be too large, perhaps due partly to an overlarge accepted value for the 7Li(d, p)8Li cross section, which has been used for normalization purposes. A decrease in the 7Be(p,)I) cross section would reduce the calculated detection rate of solar neutrinos and lessen the discrepancy with the measured value.
The Momentum Transfer Cross Section for Electrons in Mercury Vapour from 0·1 to 5 eV
Authors: Elford MT
Published: June 2013

The momentum transfer cross section for electrons in mercury vapour has been derived over the energy range 0�1-5 eV from the drift velocity data of Elford (1980). The cross section has a resonance at 0�5 eV with a maximum value of 180 A 2 (1� 8 x 10-18 m2). It is shown that previous cross sections derived either from experimental data or obtained by ab initio calculations are incompatible with the drift velocity data.
Electric Quadrupole Excitation of the First Excited State of 11B
Authors: Fewell MP , Spear RH , Zabel TH , Baxter AM
Published: June 2013

The Coulomb excitation of backscattered llB projectiles has been used to measure the reduced E2 transition probability B(E2; 3/2--+ 1/2-) between the 3/2- ground state and the 1/2- first excited state of llB. It is found that B(E2;3/2--+1/2-) = 2�1�0�4 e2 fm4, which agrees with shell model predictions but is a factor of 10 larger than the prediction of the core-excitation model.
Static Quadrupole Moment of the First Excited State of 28Si
Authors: Spear RH , Fewell MP
Published: June 2013

The reorientation effect in Coulomb excitation has been used to measure the static quadrupole moment Q2+ and B(E2;0+->2+) for the 1�779 MeV first excited state of 28Si. The results obtained are Q2+ = +15�5�3�4 efm2 and B(E2;0+->2+) = 326�20 e2fm4 ? The value obtained for Q2+ confirms the results of other recent determinations using the reorientation effect, and the B(E2; 0+ -> 2 +) value is in excellent agreement with the mean value deduced from previous lifetime determinations. Shell model and Hartree-Fock calculations of Q2+ both give a good account of the experimental result.
Internal Degrees of Freedom and Anelasticity in Glasses
Authors: Smith DA , Cookson P
Published: June 2013

An extension of the AHV-Phillips model is proposed which describes the anelastic and timedependent behaviour of glasses over a range of temperatures. The model assumes the existence of g;roups of atoms with two or more metastable locations in the matrix. Transitions between these locations are assumed to be thermally activated, and the parameters of the potential seen by such groups are assumed to be continuously distributed. The active groups are a realization of internal degrees of freedom in the sense of irreversible thermodynamics. The thermodynamic description is particularly convenient when strain couplings are involved, since Maxwell relations determine the internal contribution ,to the stress in terms of the strain dependence of the internal potentials. Several consequences of the model, such as time-dependent heat capacities, time-varying stress-strain relations etc., are investigated and found to be consistent with existing experiments. In particular, Wiedmann's elastic after-effect measurements of 1886 can be fitted and lead to values of 0�6-0�9 eV for the width of the distribution of energy barriers. However, the predicted ultrasonic attenuation from active groups conflicts with experiment, and reasons for this are discussed.
Hyperbolic Motion in Gravitational Theories
Authors: Davidson W
Published: June 2013

The equation of motion of a high speed test particle in the field of a spherical mass is discussed for a parametric range of gravitational theories, including general relativity. It is shown how in principle such hyperbolic orbits may discriminate between these theories.
On the Interface Structure in a Simple Cubic Ising System
Authors: Johnson CHJ
Published: June 2013

An examination of the delocalization of the interface in a three-dimensional simple cubic lattice-gas Ising system as a function of the temperature is made using cluster models formulated in terms of the low-order lattice correlations of the Ising system. By regarding the cluster as a sample from the infinite system, the lattice correlations used in the analysis may be computed in a self-consistent manner by taking the correlations defined for the cluster as estimates of the corresponding correlations for the infinite system: The important result to come from the present analysis is that, provided the cluster properly samples the three-dimensional nature of the infinite system, a comparatively small cluster, while not actually yielding an interface critical temperature, can be made to realize a good representation of the interface delocalization as a function of temperature.
Thick Target Gamma Yields from Fluorine
Authors: Kenny MJ
Published: June 2013

Yields have been measured of prompt y rays emitted when protons bombard a thick target containing fluorine for energies between 1?75 and 2?75 MeV. The results help to remove discrepancies in previous data. The yields are very high and the high energy y rays are easily identified. Absolute intensities have been obtained to an accuracy of � 10%. The results help to establish a data base for the quantitative analysis of fluorine.
Elastic Scattering of 152Eu ? Rays by Tungsten
Authors: Taylor RB , Teansomprasong P , Whittingham IB
Published: June 2013

Differential cross sections for the elastic scattering of 344, 444, 779, 964, 1086, 1112 and 1408 keY y rays by tungsten have been measured for six scattering angles ranging from 7� to 45� and are compared with theoretical cross sections for Rayleigh plus nuclear-Thomson plus, for the 1408 keY case, Delbriick scattering. For small momentum transfers the experimental results are in best agreement with cross sections computed using the Hartree-Fock form factor Rayleigh amplitudes, but at large momentum transfers the experimental results lie below these theoretical cross sections and also those computed using both the 'exact' Rayleigh amplitudes of Kissel and Pratt and the Dirac point-Coulomb form factor amplitudes. Inclusion of the Papatzacos and Mork Delbruck amplitudes at 1408 keY reduces the difference between experimental and theoretical cross sections for scattering angles less than 25�, but worsens the situation for larger angles.:
Oscillator Strengths, Transition Probabilities and Lifetimes involving 2p3p States in OV
Authors: Glass R
Published: June 2013

Configuration interaction wavefunctions are used to calculate energy separations, wavelengths, oscillator strengths (length and velocity forms), transition probabilities (length form) and lifetimes for absorption transitions to the 2p3p 1.3L [L = 0, 1,2] states for 0 V. omparison with recent beam-foil experimental data is generally good. A common set of radial functions is used.
Multiple Scattering in Neutron Polarization Analysis
Authors: Wells P , Cywinski R
Published: June 2013

An analytical method of correcting measured neutron polarization analysis spectra for .multiple scattering effects is presented. The multiple scattering corrections are applicable to any general instrumental and specimen geometries, and have been evaluated within the elastic quasi-isotropic scattering approximation. The results are appropriate for specimens where the total attenuation of the incident neutron beam is smalland where the multiple scattering is no more than about 20% of the total scattered intensity. Specific results have been calculated for the geometry of the LONGPOL polarization analysis instrument at the AAEC Research Establishment, and the theoretical predictions have been tested by examination of the neutron spin-dependent cross sections of a vanadium standard specimen measured using LONGPOL. Finally, the use of the analytical multiple scattering corrections is illustrated by reference to some recent measurements of spin-dependent cros-s sections-of anMnCu alloy obtained on LONGPOL
Theory of Coaxial Wave Guides with Dielectric and Magnetic Discontinuities
Authors: Wilhelm HE , DuBow JB , Singh P
Published: June 2013

Analytical solutions are derived for the electromagnetic E, Hand T waves in coaxial wave guides of inner radius a and outer radius b and of infinite length, which are filled in the direction of propagation z with media of different electric permittivity 8 and magnetic permeabilityjz such that: 8 = 8b Il = III for - CIJ ~ Z < - d; 8 = 82, Il = 112 for - d < z < +d; 8 = 83, Il = 113 for +d < z ~ + CIJ. The power reflection and transmission coefficients of the E, Hand T waves are given as a function of frequency Q) and the guide parameters 81, Ill, a, band d. It is shown that the reflection and transmission coefficients exhibit a periodic fine structure in the frequency space above the 'cutoff frequency as a result of the spatial eigenvalue nature of the field solutions. The theory presented provides analytical foundations for the measurement of the frequency-dependent electric permittivity and magnetic permeability of samples in coaxial wave guides.