bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating the accuracy of the Agricultural Production Systems Simulator (APSIM) simulating growth, development, and herbage nutritive characteristics of forage crops grown in the south-eastern dairy regions of Australia
Authors: Pembleton K. G. , Rawnsley R. P. , Jacobs J. L. , Mickan F. J. , O'Brien G. N. , Cullen B. R. , Ramilan T.
Published: June 2013

Pasture-based dairy farms are a complex system involving interactions between soils, pastures, forage crops, and livestock as well as the economic and social aspects of the business. Consequently, biophysical and farm systems models are becoming important tools to study pasture-based dairy systems. However, there is currently a paucity of modelling tools available for the simulation of one key component of the system—forage crops. This study evaluated the accuracy of the Agricultural Production Systems Simulator (APSIM) in simulating dry matter (DM) yield, phenology, and herbage nutritive characteristics of forage crops grown in the dairy regions of south-eastern Australia. Simulation results were compared with data for forage wheat (Triticum aestivum L.), oats (Avena sativa L.), forage rape (Brassica napus L.), forage sorghum (Sorghum bicolor (L.) Moench), and maize (Zea mays L.) collated from previous field research and demonstration activities undertaken across the dairy regions of south-eastern Australia. This study showed that APSIM adequately predicted the DM yield of forage crops, as evidenced by the range of values for the coefficient of determination (0.58–0.95), correlation coefficient (0.76–0.94), and bias correction factor (0.97–1.00). Crop phenology for maize, forage wheat, and oats was predicted with similar accuracy to forage crop DM yield, whereas the phenology of forage rape and forage sorghum was poorly predicted (R2 values 0.38 and 0.80, correlation coefficient 0.62 and –0.90, and bias correction factors 0.67 and 0.28, respectively). Herbage nutritive characteristics for all crop species were poorly predicted. While the selection of a model to explore an aspect of agricultural production will depend on the specific problem being addressed, the performance of APSIM in simulating forage crop DM yield and, in many cases, crop phenology, coupled with its ease of use, open access, and science-based mechanistic methods of simulating agricultural and crop processes, makes it an ideal model for exploring the influence of management and environment on forage crops grown on dairy farms in south-eastern Australia. Potential future model developments and improvements are discussed in the context of the results of this validation analysis.
Theoretical Answers to Some Experimental Questions about Gaseous Ion Transport
Authors: Viehland Larry A.
Published: June 2013

It is shown that the diffusion coefficients parallel to the electric field in
an ion swarm experiment are greater than the perpendicular diffusion
coefficients at low values of E/N, the ratio of the
electric field strength to the gas number density, but that at high
E/N the two are approximately equal or the inequality is
reversed. For electron swarms the inequalities are the reverse of those for
ion swarms, unless there is a significant Ramsauer minimum in the
momentum-transfer cross section. A second point is that for many
ion–atom systems the zero-field mobility is not close to its
polarisation limit even when the gas temperature is 4.35 K. It is also shown
that the unusual mobilities observed for Ar+ ions in He
gas at 4.35 K are not due to quantum-mechanical (resonant scattering) effects
as postulated by the experimenters. Finally, it is shown that it is possible
to compute gaseous ion transport coefficients for molecular ions from a
knowledge of the fundamental interaction potentials rather than from assumed
models for the cross sections.
Quantitative Theory and Accurate Experiments: Low-energy Electron Scattering by He and H2 as Case Studies
Authors: Nesbet Robert K.
Published: June 2013

Accurate low-energy electron scattering data are needed in many fields of
physics. However, accurate experiments are difficult to design and to carry
out. By 1967 low-energy electron–He cross sections had been measured by
two different techniques, designed to provide accurate data. Unfortunately,
the data differed by amounts well outside the estimated error bars. Despite
the relative simplicity of the He atom, decisive theoretical calculations on
the e–He system could not be done with methods available in 1967. After
a decade of development of theoretical methodology it became possible in 1979
to carry out calculations with absolute estimates of residual error limits.
The results were found to agree closely with the momentum transfer cross
section deduced from electron swarm data and with recent beam data by improved
techniques, but were inconsistent with the original beam data of 1965. More
recently, a similar conflict exists between data measured for electron-impact
vibrational excitation of the hydrogen molecule by electron swarm and beam
techniques. This conflict has persisted despite great progress in beam
scattering techniques and in theoretical methods. A brief review of the
relevant electron scattering theory will be given.
Magnetism and Neutron Scattering
Authors: Hicks T. J.
Published: June 2013

Magnetic neutron scattering is very closely connected to the fundamental
magnetic quantities of magnetisation and susceptibility. This is because, to a
very high degree of approximation which becomes exact at long neutron
wavelengths, the interaction of the neutron magnetic dipole moment is with the
local magnetic induction in the magnetic material. The strength of neutron
scattering for the investigation of magnetic materials lies in this and the
facility of the technique to probe Fourier components of the moment and the
susceptibility with wavelengths down to atomic distances, as well as to probe
susceptibility fluctuation time scales the same as those that are thermally
excited. This paper provides a concise account of the formal connection
between neutron scattering cross sections and more familiar bulk magnetic
parameters.
Planetary-scale Coherent Structures of Tropical Moist Convection
Authors: Yano Jun-Ichi
Published: June 2013

Two competing pictures for planetary-scale moist convective coherency in the
tropical atmosphere exist. The nonlinear turbulent picture emphasises the
scaling nature of the system, whereas the traditional picture emphasises the
characteristic scales associated with the variability. Some idealised
simulations were performed as an initial attempt to reconcile these two
competing pictures.
Application of DFT and EMS to the Study of Strained Organic Molecules
Authors: Adcock W. , Brunger M. J. , Michalewicz M. T. , Winkler D. A.
Published: June 2013

Electron momentum spectroscopy (EMS) studies of the valence shells of
[1.1.1]propellane, 1,3-butadiene, ethylene oxide and cubane are
reviewed. Binding energy spectra were measured in the energy regime of
3·5–46·5 eV over a range of different target electron
momenta, so that momentum distributions (MDs) could be determined for each ion
state. Each experimental electron momentum distribution is compared with those
calculated in the plane wave impulse approximation (PWIA) using both a
triple-? plus polarisation level self-consistent field (SCF) wave function
and a further range of basis sets as calculated using density functional
theory (DFT). A critical comparison between the experimental and theoretical
momentum distributions allows us to determine the ‘optimum’ wave
function for each molecule from the basis sets we studied. This
‘optimum’ wave function then allows us to investigate chemically
or biologically significant molecular properties of these molecules. EMS-DFT
also shows promise in elucidating the character of molecular orbitals and the
hybridisation state of atoms.
Optical Investigation of La1-xCaxMnO3 and La1-xLixMnO3
Authors: Lewis R. A. , Martin A. D. , Wang X. L. , Dou S. X.
Published: June 2013

An optical study has been made of
La0·7Ca0·3MnO3
and
La0·8Li0·2MnO3
in the infrared spectral region (100 cm-1 to 4000
cm-1). The transmission of all samples is negligible.
The photoconductive response is also unmeasurable. The data reported are
therefore restricted to reflectivity measurements. At room temperature, both
materials exhibit similar ‘bending’ and ‘stretching’
phonon modes, associated with the MnO6 octahedra, at
~330 and ~580 cm-1, respectively. The
‘external’ phonon mode observed at ~170
cm-1, corresponding to the (La,Ca/Li) cations
beating against the MnO6 octahedra, is slightly shifted
between the two materials, as would be expected on the basis of the different
compositions. At elevated temperature (~600°C) the intensity of the light
reflected decreases across the infrared spectrum, and the
‘stretching’ mode moves to lower energy.
Investigation of Lattice Effects in Rare Earth Manganites by 18O-isotope Exchange
Authors: Mahesh R. , Itoh M.
Published: June 2013

The strong coupling between the electron spin and lattice arising from the
Jahn-Teller effect of manganese ions plays an important role in the mechanism
of colossal magnetoresistance and related properties of the rare earth
manganites. The lattice effects in this class of oxides have been extensively
studied through the application of hydrostatic as well as chemical pressures
and magnetic fields. The recently observed giant 18O
isotope effect provides direct evidence for the formation of lattice polarons
in manganites. Here we report the preliminary results of our investigations on
a variety of normal as well as 18O isotope-exchanged
perovskite manganites exhibiting colossal magnetoresistance and charge
ordering. The observed isotope shift of
Tc as well as that of
Tco is correlated with the key
parameters controlling the lattice such as the Mn
3+ content, the average ionic radius of the A-site
cation ⟨rA⟩ , and the
A-site ionic size disorder σ2 .
Australian Journal of Physics Astrophysical Supplement
Authors: Goss WM , Shaver PA
Published: June 2013

Contour maps of 63 regions in the galactic plane are presented. The half-power beamwidth was 4' arc at 5000 MHz. Positions and composite flux densities are given for 206 sources.
Electron Energy-loss Spectra of the Alloys Al?Mg, Cd?Mg, and Cu?Ni
Authors: Hartley BM , Swan JB
Published: June 2013

Characteristic electron energy-loss spectra of the alloys AI-Mg, Cd-Mg, and Cu-Ni are presented. These spectra are interpreted in terms of expected changes in the band structures of the pure metals on alloying.
The Galactic Magnetic Field and Cosmic Rays
Authors: Piddington JH
Published: June 2013

The structure of the magnetic field of the Galaxy and other spiral systems and the inseparable problem of the origin of cosmic rays are examined: (1) A variety of evidence is used to show that the galactic field extends far beyond the disk and connects the disk field with a general field fixed in the local system of galaxies. (2) The coronal field extends beyond 10 kpc as an oblique helix which is constantly expanding, and has partially force�free characteristics.
On the Theory of Type II and Type III Solar Radio Bursts. II. Alternative Model
Authors: Melrose DB
Published: June 2013

It is argued that observational data on type III bursts point to the exciting agent for a burst being a bunch of fast electrons which experience no strong two� stream instability. Ways in which the two�stream instability might be suppressedare discussed.
Australian Journal of Physics Astrophysical Supplements
Authors: Landecker TL , Wielebinski R
Published: June 2013

A survey of the sky between S + 25� and S - 25� at 85 and 150 MHz is described, made with aerial beams 3.8� X 3.5� and 2.2� X 2.2�. Absolute measurements of aerial temperature are tabulated for points spaced 2�. A computer program is described which has enabled these results to be reduced to brightness temperatures, which are tabulated for the same points.
Calculation Of The 12C+a Capture Cross Section at Stellar Energies
Authors: Barker FC
Published: June 2013

The 12C(0:, y) 160 cross section is calculated at stellar energies, using R-matrix parameters obtained by fitting consistently the 12C+", scattering phase shifts and the ",-spectrum from 16N f:l-decay. This limits the 12C+", channel radius to the range 5-7 fm. The S-factor at Eo< = 400 keV is calculated to lie in the range 0�05-0,33 MeV.b.
Finite Rest Masses of Wave Quanta in Material Media
Authors: Cole KD
Published: June 2013

The equivalence of a dispersion relationship and Einstein's mass--energy relationship leads to the specification of a particle in a vacuurrt which is equivalent to a "photon" in a medium. The invariance of the rest mass of this particle leads to a formula for the Doppler effect which is good for all forms of waves whose quanta can be described by E = nw and p = nk. Applying dynamical equations to the equivalent particle in the case of a radiofrequency photon in a plasma around a star, a new gravitational redshift formula is deduced which reduces to the well-known expression in the appropriate limit. A new form of bending of photon trajectories in a gravitational field is also described. At frequencies near the plasma frequency Vp the bending is vp/4(v-vp} times that for light in a vacuum.
A Method for Determining the Electron Density Distribution about the F2 Peak of the Ionosphere
Authors: Dyson PL
Published: June 2013

A method is given for extending the analysis of topside ionograms to yield ionospheric electron density profiles down to and below hmax, the peak of the F2 layer, by analysis of the ground echoes. Calculations using model ionospheres indicate that the accuracy of the method is not seriously affected by the assumptions made or by the limited accuracy with which ionograms can be scaled.
Approximate Solutions of the Relativistic Gravitational Field Equations to Describe Clusters of Galaxies
Authors: Cook MW
Published: June 2013

Approximate solutions to the Einstein field equations are found which describe a spherically symmetric inhomogeneity in a general Robertson?Walker model, i.e. one with an arbitrary equation of state. The approximation hypothesis is that the pressure deviates only slightly from uniformity, and it is found that the density may have quite large local fluctuations, e.g. by a factor of 106 over a region 10-2 Mpc in diameter. Reference is made to observed data to determine which categories of stellar objects may be described by the results.
Compound Nucleus Formulation of Reaction Matrix Theory
Authors: Cook JL , Bertram WK
Published: June 2013

It is shown that multilevel resonance parameters for each element of the reaction matrix cannot be determined from available data. However, additional constraints may be introduced without affecting agreement with experiment. The Bohr compound nucleus hypothesis, which states that the modes of formation and decay of a compound nucleus are independent, is applied to the T-matrix and it is found, as in Newton's model, that the channel matrix can be inverted analytically to provide simple formulae for cross sections, for both the real Wigner?Eisenbud reaction matrix and Moldauer's complex reaction matrix. Wigner?Eisenbud theory leads directly to Newton's strong correlation model and its unacceptable consequences. Moldauer's theory does not, however, and can explain cross section behaviour adequately while being consistent with Bohr's hypothesis. Cross sections can be written as a sum of single level contributions, as in the Adler?Adler formulation. Finally, Moldauer's statistical theory is shown to be applicable, and expressions are derived for the �averaged cross sections as functions of the complex Moldauer resonance parameters.
The Radio Continuum of the Large Magellanic Cloud. II. Continuum Observations at 11 cm Wavelength
Authors: Broten NW
Published: June 2013

Contour diagrams are presented for the radio continuum brightness of the Large and Small Magellanic Clouds observed at a wavelength of 11 cm. The observations were made with the Parkes 64 m radio telescope, whose half-power beamwidth was 7'�35 arc.
On Magnetic Inhibition of Thermal Convection
Authors: Van der Borght R , Murphy JO , Spiegel EA
Published: June 2013

The effect of an imposed vertical magnetic field on convective transfer in a horizontal Boussinesq layer of fluid heated from below is studied in the mean field approximation. Solutions are found over a wide range of conditions, for free boundaries, by a combination of numerical and analytic techniques. Quantitative estimates are made of the significant modifications to the heat transfer which are brought about by the presence of the magnetic field. It is found that the general properties of nonlinear steady cellular convection seem to persist in the face of magnetic inhibition.
Australian Journal of Physics Astrophysical Supplements
Authors: Day GA , Caswell JL , Cooke DJ
Published: June 2013

The results of observations of the galactic plane in the longitude ranges 46� to 61� and 190� to 290� undertaken with the 64 m (210 ft) radio telescope of the Parkes Observatory are given in the form of contour maps and a list of 343 radio sources. At the observing frequency of 2700 MHz the half-power beamwidth was 8'�2 arc. Some individual sources are discussed in detail. The present results together with those already published complete the Parkes 11 cm survey of the galactic plane.
Quantum Electrodynamics of Particles with Arbitrary Spin
Authors: Green HS
Published: June 2013

A generalization of quantum electrodynamics is developed for particles of higher spin, with careful attention to the requirements of consistency, causality, unitarity and renormalizability. It is shown that field equations studied previously by the author are expressible in arbitrarily many different forms, which are equivalent in the absence of electromagnetic interactions, but not when electromagnetic coupling is introduced in a gauge-invariant way. A form is chosen which satisfies the requirements of causality. It is shown how to define a particle density, which is positive-definite in the subspace spanned by solutions of the field equation, and satisfies a Lorentz-invariant conservation law. The quantization and renormalization of the resulting electrodynamics is studied, and is found to require only minor modifications of the existing theory for particles of spin t.
A Balloon Investigation of Galactic ?-ray Lines with a High Resolution Ge(Li) Spectrometer
Authors: Yoshimori M , Watanabe H , Okudaira K , Hirasima Y , Murakami H
Published: June 2013

Galactic y-ray lines have been investigated with a balloon-borne Ge(Li) spectrometer. The galactic plane was surveyed over the longitudinal interval 40�_210�, but upper limits only were obtained for the intensities of y-ray lines from positron annihilation at 0�511 MeV and the nuclear decays of 2�Ne� (1� 634 MeV), 24Mg* (1�369 MeV), 28Si* (1� 779 MeV) and S6Pe� (0�847 MeV). These upper limits are of the order of 10-3 photons cm-2 S-l sct, which are consistent with measurements for other lines observed so far. A possible y-ray line feature at 400 keV, with a flux of (7 �4� 5 �4) x 10-3 photons cm-2 s-t, was detected when the Crab Nebula was in the field of view. This line seems to be identical with one reported by Leventhal et al. (1977), who suggested that it may originate from a gravitational redshift of the 0�511 MeV annihilation line produced near the surface of the neutron star.
Ratio of Sheath Thickness to Debye Length for a Slightly Ionized Continuum Plasma
Authors: A Hamilton John
Published: June 2013

The penetration of plasma sheaths for spherical probes in a slightly ionized continuum plasma has been computed for values of 8 (the ratio of ion to electron temperature) of 0�01 and 1�0 with pp (the ratio of probe radius to plasma Debye length) set at 5, 10, 20 and 30. Values of the potential drops at the sheath boundaries are presented.
Mode Coupling in the Solar Corona. VI. Direct Conversion of Langmuir Waves into o-mode Waves
Authors: Melrose DB
Published: June 2013

Fundamental plasma radiation can result from direct coupling of Langmuir waves into o-mode waves in an inhomogeneous magnetized plasma. The coupling occurs for Langmuir waves propagating nearly along the direction of increasing plasma density, and the resulting o-mode waves propagate towards lower plasma densities. An analytic theory for the coupling (which is of z-mode waves into o-mode waves) is developed using approximate solutions of the Booker quartic equation. The results are shown to agree with the results of numerical calculations for the 'Ellis window' in 'the generation of the z trace in the terrestrial ionosphere. This 'direct conversion' of Langmuir waves into o-mode waves is an alternative mechanism for fundamental plasma emission, possibly replacing or supplementing the more familiar scattering from the charge clouds around thermal ions. Possible applications of 'direct conversion' to various solar radio bursts are explored, but for none is it found to be more favourable than alternative mechanisms.
The Drift Velocity of Low Energy Electrons in Oxygen at 293 K
Authors: D Reid Ivan , W Crompton Robert
Published: June 2013

A new drift tube technique incorporating electron density sampling to locate the drifting electron swarms has been used to measure electron drift velocities in the range 0.14–1.4 Td. The data were obtained at several pressures from 0.2 to 0.5 kPa. The estimated accuracy ranges from 2% at 1.4 Td to 5% at 0.14 Td.
Parametric Instabilities in a Magnetized and Collisional Plasma
Authors: Phalswal DR , Dube Anil
Published: June 2013

The dispersion relation for a magnetized, collisional and hot plasma in the presence of a pump wave is developed for the case where the pump frequency Wo is large compared with the cyclotron frequency Wc and the plasma frequency Wp. Formulae for the growth rate, the damping rate for the free electron plasma wave and the threshold power are derived and discussed numerically under different conditions. It is found that in a hot plasma (for magnetic fields with wc/wp = 1 and 10) the threshold power PT is less than or greater than that in a cold plasma for the (Rew2)+ or (Rewz)_ modes respectively. In a weak magnetic field (wc/wp = 0�1), PT does not vary with the direction B of the magnetic field or the (Rewz)+ mode. However, PT for the (Rewz)_ mode is a minimum at B = 30� and 10� for c/wp = 1 and 10 respectively, and it becomes very large (105-107 times its value in a cold unmagnetized lasma) for wc/wp = 0�1. The results for the growth rate are found to be just the reverse of hose for the threshold power.
The Orbit?Lattice Interaction for Lanthanide Ions. II. Strain and Relaxation Time Predictions for Cubic Systems
Authors: Newman DJ
Published: June 2013

An analysis of dynamic crystal field data for cubic systems is carried out in order to assess the possible usefulness of the superposition model in understanding the results of lattice strain and spin-lattice relaxation experiments. The data used in this work are the electron paramagnetic resonance (EPR) results for strained cubic crystals obtained by Buisson, Baker and their coworkers, and the spinlattice relaxation results obtained by Buisson, Stapleton and their coworkers. A method of generalizing the superposition model to take into account long range electrostatic contributions without introducing additional unknown parameters is proposed, and shown to give consistent results. It is concluded that differences between bulk and local strains must be taken into account in any model of the dynamic crystal field, if it is to achieve success.
Mass Splitting of Beautiful Baryons in Broken SU(4) in the Non-strange Sector
Authors: Ahmad Mubarak , Sofi GQ
Published: June 2013

Broken SU(4) symmetry is exploited to derive mass relations between t + and t + baryons carrying nbeauty quantum numbers. These relations are obtained in the non-strange sector of SU(4). Weight diagrams are drawn to show the derived relations.
45Sc(p, p')45Sc and the Attainment of a Thermal Distribution of States in an Astrophysical Environment
Authors: Anderson MR , Kennett SR , Sevior ME , Sargood DG
Published: June 2013

Cross sections for inelastic scattering of protons by 45SC have been measured over the energy range Ep = 1?2-2? 5 MeV for protons leading to the second, third, fourth, sixth and eighth excited states of 45SC. Statistical model calculations are' in good agreement with the data. Further statistical model cross section calculations are used in an investigation of the part played by inelastic and superelastic scattering of protons in bringing about a thermal distribution of states in 45SCin a stellar interior under the conditions of explosive silicon burning. This mechanism is found to be effective for temperatures above 4? ?x 109 K
Spatially Homogeneous and Anisotropic Cosmological Models in Brans-Dicke Theory
Authors: Johri VB , Goswami GK
Published: June 2013

Spatially homogeneous and anisotropic cosmological models corresponding to Bianchi type I solutions of Brans-Dicke theory are investigated. The physical and geometrical properties of the models are discussed and compared with the corresponding relativistic models.
Photon Correlation Spectroscopy Using Optical Heterodyne Detection
Authors: C Fletcher Guy , I Harnett Julienne
Published: June 2013

The detection by optical heterodyning of laser light scattered from solutions of macromolecules offers significant improvement in statistical accuracy over the more usual self-beating method. Nevertheless the heterodyne technique is not commonly used because of the supposed ifficulties associated with stable and efficient mixing of the scattered light with a local oscillator beam. We have carried out an experimental comparison of several methods of mixing the two beams, using very dilute solutions of polystyrene latex spheres as scatterers. Experimental data are also presented for the apparent particle radius as a function of the local oscillator level, and are compared with theoretical predictions.
Thermosolutal Instability of a Hall Plasma
Authors: Sharma RC , Sharma KN
Published: June 2013

The thermosolutal convection in a layer of viscous plasma heated from below and subjected toa stable solute gradient is investigated in the presence of Hall currents. For the case of stationary convection, the stable solute gradient and the Hall currents are found to have stabilizing and destabilizing effects respectively on the system. The question of the onset of instability as overstability is also discussed
New Optical Identifications from the Parkes 2700 MHz Resurvey of the ± 4° Declination Zone
Authors: Savage Ann , Bolton JG , Trett Jenny
Published: June 2013

Identifications are suggested for 59 radio sources from the resurvey of declination zone �4�, 27 with galaxies and 32 with stellar objects; 19 of the latter are confirmed as quasi-stellar objects (QSOs). The identifications were made from the Palomar Sky Survey prints plus supplementary plates taken with the Palomar and U.K. Schmidt telescopes and the Anglo-Australian 3�9 m telescope.
GDR Contribution to Coulomb Excitation. II. 17O
Authors: Barker FC
Published: June 2013

The contribution to the Coulomb excitation of the first excited state of 170 due to virtual excitation of the giant dipole resonance (GDR) is calculated, using shell model wavefunctions for the ground and first excited states. A large value is obtained.
Thermodynamic Studies and Magnetic Ordering of Ni-Cr Alloys Close to the Critical Composition
Authors: Simpson MA , Smith TF
Published: June 2013

We report measurements of the specific heat capacity and the thermal expansion for Ni-Cr alloys in the vicinity of the magnetic ordering temperature TM and at lower temperatures. No evidence of a contribution due to the magnetic ordering is found in the specific heat capacity and only the indication of a small contribution in the thermal expansion near to T M for an Ni 11 at. % Cr alloy. A significant contribution of magnetic origin is seen for both quantities at lower temperatures. Values for the magnetic Grlineisen parameter yi, are derived from the specific heat capacity and thermal expansion data and compared with values of dIn TM/d In V obtained from direct easurements of dTM/dP. Both yi, and - d In TM/d In V are large and negative for weakly ferromagnetic alloys but differ numerically, whereas for paramagnetic alloys yi, is large and positive.
Orientation of He(21P) by Electron Impact Excitation and Polarization of the Radiative Decay
Authors: Golden DE , Steph NC
Published: June 2013

A general description of electron-photon angular correlations is given which relates the quantummechanical observables to the structure of the coherently excited state. The wavefunction is expressed in terms of magnetic sublevel amplitudes and state vectors. A semiclassical impact parameter model of orientation is introduced, the experimental considerations are discussed, and experimental results for the orientation and polarization fraction are reviewed.
Rotational and Vibrational Transitions in Molecular Collisions
Authors: Peter Toennies J
Published: June 2013

Recent progress in understanding collision processes involving rotational and vibrational excitation in collisions of atoms (ions) with molecules in terms of simple models is illustrated for two systems. Rotational excitation of N2 in collision with He at 27 meV can be explained by an optical model. A more quantitative agreement is achieved by cross sections calculated exactly for the model potential of Tang and Toennies. Vibrational excitation probabilities for resolved single mode excitation of CF4 in small angle 10 eV ion collisions follow a Poisson distribution indicating a breathing sphere forced oscillator behaviour
The Room Temperature Elastic Constants of Caesium Thiocyanate
Authors: Irving MA , Prawer S , Smith TF , Finlayson TR
Published: June 2013

The velocities of propagation of elastic waves in caesium thiocyanate have been measured along the three orthorhombic axes and normal to the (110), (011) and (101) planes using a double-transducer technique at 10 MHz. The velocities are found to be consistent with the orthorhombic crystal symmetry, and in favourable agreement with a recently published rigid-ion model calculation. The calculated elastic stiffness constants have values C11 = 18'9�0'7, C22 = 20�6�1�0, C33 = 28�1�1�6, C44 = 1'96�0'05, Css = 7�30�0�2, C66 = 3�04�0�07, C12 = 7'8�4'3, Cl3 = 14�8�4 and e23 = 6�3�4GPa. The calculated values for the adiabatic bulk modulus and the low temperature limiting value of the Debye temperature are 13�2 � 3�5 GPa and 132 K respectively
Method of Averaged Lagrangian for Precessional Rotation and Other Complementary Effects of Waves in Nonlinear Plasmas
Authors: Chakraborty B , Paul SN
Published: June 2013

The formalism of the averaged Lagrangian has been extended and developed to evaluate the intensitydependent precessional rotation and wave number shift of an elliptically polarized electromagnetic wave in unmagnetized cold relativistic plasmas; the results are identical to those of Arons and Max (1974) and others. Moreover, the expression for two intensity-induced nonlinear modulation frequencies for both the right and left circular polarization components of the wave have been derived. The mathematical technique developed here may be useful in the study of other types of nonlinearly evolved rotational corrections for motions in fluids, and so the possibilities of broadening the scope of this formalism are discussed.
Theory of Heavy-ion Elastic Collisions Revisited
Authors: Mohr CBO
Published: June 2013

The literature on the strong absorption theory of heavy-ion elastic collisions contains a discrepancy involving a singularity in the scattering amplitude at the critical angle qc. The formulae concerned have been carefully derived ab initio and the obscurity removed. The validity of the approximations for the scattering amplitude at angles less than and greater than qc has been examined. The insight gained has made it possible to investigate further the effect of refraction, and to consider the behaviour of the real part of the nuclear phase.
Molecular Dynamics of the Phase Transition in Deuteroammonium Chloride
Authors: Pandey Sadhana , Trikha SK
Published: June 2013

Computer simulation studies have been made to investigate the phase transition in ND4CI at low temperature. Two different types of potential have been used to represent the interaction between NDt and CI-: (i) the Lennard Jones potential and (ii). the twelfth inverse power or r -12 repulsive potential. The present study reveals the occurrence of a phase transition in N-D4CI in a well-defined region. The Lennard Jones potential appears to be more appropriate in depicting the two welldefined phases known as II and III in the literature. The energy pattern curves obtained in this study give us the nature of the rotational behaviour of ND:' before and after the transition at 249 K. The libration frequency of the NDt ion is estimated to be of the order of 130 em-1.
Refraction in Elastic Collisions of Heavy Ions
Authors: Mohr CBO
Published: June 2013

We attempt to improve our understanding of the processes of absorption and refraction in heavy-ion elastic collisions. The WKB method for a complex potential provides a link. The results account for certain observed features of the scattering angular distributions.
Low Energy Ion?Surface Interaction ? Atomic Physics in an Ordered Atom Environment
Authors: MacDonald RJ , O'Connor DJ
Published: June 2013

Ion-surface interactions have application within a number of areas of contemporary physics research. In particular, it is essential that an understanding of the interaction between an ion and a solid surface in a fusion reactor environment be achieved. A detailed understanding of the interaction is also essential for quantitative application of several of the modern methods of surface analysis currently available. It is unfortunate that the necessary level of understanding of the interac
Power and Momentum Relations in Rotating Magnetic Field Current Drive
Authors: Hugrass WN
Published: June 2013

The use of rotating magnetic fields (RMF) to drive steady currents in plasmas involves a transfer of energy and angular momentum from the radio frequency source feeding the rotating field coils to the plasma. The. power-torque relationships in RMF systems are discussed and the analogy between RMF current drive and the polyphase induction motor is explained. The general relationship between the energy and angular momentum transfer is utilized to calculate the efficiency of the RMF plasma current drive. It is found that relatively high efficiencies can be achieved in RMF current drive because of the low phase velocity and small slip between the rotating field and the electron fluid.
Poloidal Flow in Axisymmetric Pulsar Magnetospheres
Authors: Burman RR
Published: June 2013

This paper deals with dissipation-free flow in steadily rotating axisymmetric pulsar magnetospheres; for each species, relativistic inertia is balanced by the Lorentz force. Knowledge of integrals of the motion, including a complete integral for the limiting case of purely toroidal flow, is used to manipulate the fundamental electromagnetic and hydrodynamic equations into convenient forms. Consideration of the flow dynamics, incorporating plasma drift across the magnetic field and injection along it, provides the physical basis of a description of flow in which the poloidal motion is closely tied to the poloidal magnetic field lines (L. Mestel el al. to be published 1985). Particular attention is paid to flows whose toroidal part tends towards corotation as the symmetry axis is approached, and implications of the results for model building are discussed.
Symmetry of Terms in the Temperature Factor for Bragg Diffraction of X Rays or Neutrons
Authors: Mair SL
Published: June 2013

Terms in the anharmonic Debye-Waller factor, taken as a perturbation about the harmonic case to second order in the van Hove ordering parameter, are classified according to the point-group symmetry of the vibrating atom. The classification is valid for a fully interacting (many-body) crystal potential. It is pointed out that certain terms, which are symmetry-allowed for such a general crystal potential, are excluded if an effective one-particle potential is employed.
Reflection of Magnetoionic Waves from a Steep Density Gradient. I. Incident Extraordinary Mode
Authors: Hayes LM
Published: June 2013

Calculations ofthe relative magnitudes of the four secondary waves produced when a magneto ionic wave encounters an electron density discontinuity within an anisotropic plasma are presented. We identify the different conditions under which each of the secondary waves is the dominant mode, and determine some general properties of the reflection process.
X-ray Propagation in Strongly Magnetized Plasmas
Authors: Kirk JG , Cramer NF
Published: June 2013

A new treatment of the calculation of the dielectric tensor of a magnetized plasma in an extremely strong field, such as occurs in magnetized neutron stars, is presented. An accurate numerical scheme for the evaluation of the hermitian and antihermitian parts of the tensor is used to calculate the refractive index and absorption cross section for magnetic fields and plasma temperatures typical of pulsating X-ray sources and y-ray burst sources.
Evolution of Weak Solar Magnetic Fields
Authors: Zirin Harold
Published: June 2013

We review studies of the evolution of weak solar magnetic fields with the Big Bear videomagnetograph. To all detectable limits, the field is clumped in small elements. The size of the smallest detectable intranetwork elements is probably 3x 1015 Mx (==3x 107 Wb) and the field strength in these elements probably less than 10 G (1 G == 10--4 T). The general weak network fields are the remnants of ephemeral regions, which also playa role in field diffusion as proposed by Marsh. The intranetwork elements show a shorter lifetime and much more rapid motion than the network elements. In some cases they stream into existing network elements and may merge to form new elements, but many show no preferential motion to the network edges. Consonant with X-ray bright point counts, there appear to be fewer ephemeral regions in magnetically active areas.
Phonon Spectrum of Ternary Alloys
Authors: Nayak P
Published: June 2013

Recently measurements on the infrared and Raman scattering spectra of several quaternary alloy systems such as Ga 1 _ xAI xAs 1 _ yP y have been reported. Depending on the concentration, this system can be thought of as either a GaAs-rich quaternary, where GaAs is the host containing the two kinds of impurity Al and P, or as a GaP-rich quaternary, where GaP is the host and Al and As are two impurities. Thus, the properties of such systems can be simulated by a ternary alloy. The coherent potential approximation (CPA) for ternary alloys proposed by Scarfone (1973) is used to analyse the experimental data, assuming a single Einstein oscillator model for the host crystal. The theory, consisting of both diagonal and off-diagonal randomness, agrees well with the observed values, but fails to predict the observed pair modes.
Photoionisation Cross Sections of Chlorine Atoms and Molecules at 584 Å
Authors: van der Meer WJ , Butselaar RJ , de Lange CA
Published: June 2013

A recently developed modulation method is used to obtain cross sections for the photoionisation of ground state neutral to ground state ionic, atomic and molecular chlorine relative to that of the HCl + (X2n 1IZ,3IZ) +-- HCl(XI ~ +) transition at the He Ia wavelength. With the known absolute cross section of the latter process, determined by (e,2e) coincidence spectroscopy, the present ell,periments provide absolute photoionisation cross sections of the CI + epz,l,o) +-- Clep) and Cli (XZ n g, 1IZ,3 IZ) +-- Clz (X I ~ t) transitions. Relative cross sections, previously determined for the transitions to the additional Cl and Clz ionic states accessible with He Ia radiation, are used to obtain absolute cross sections for the Cl+(IDz, ISO) +-- Clep) and Cli(AZnu,1IZ,3IZ, BZ~t) +-- Clz(XI~t) ionisation processes.
Photoionisation and Auger Electron Emission from the Lithium Molecule: Calculations using Multicentre Numerical Continuum Functions
Authors: Larkins FP , Richards JA
Published: June 2013

A numerical method has been used for the generation of molecular continuum wavefunctions at the relaxed Hartree-Fock level associated with the photoionisation of the lithium molecule. Exchange between the continuum electron and the ion core is included, but L coupling is neglected. Cross sections for core and valence shell photoionisation have been calculated from threshold to 6�0 a. u. The results differ significantly in detail from previous multiple scattering calculations. Continuum phase shifts and the asymmetry parameters for the various processes are also reported. The molecular cross section values are compared with atomic cross sections calculated at the relaxed Hartree-Fock level. The Li2 molecular Auger transition rates are also calculated from first principles using the appropriate two-centre continuum functions. The results provide a basis for the reinterpretation of recent experimental findings of photoemission data for the lithium vapour system.
Quantum Electrodynamics in Strong Magnetic Fields. IV. Electron Self-energy
Authors: Parle AJ
Published: June 2013

The electron self-energy in a magnetic field is calculated with the effect of the field included exactly. A new representation of the wavefunctions and other quantities is defined, in which the mass operator has a particularly simple form. After renormalisation, the form of the mass operator allows corrections to the Dirac equation, wavefunctions, vertex function and the electron propagator close to the mass shell to be calculated to lowest order in the fine structure constant. The probability for an electron to change spin while remaining in the same Landau level is calculated, and is found to be much less than the probability of cyclotron emission.
Spectral Behaviour of Pulse Width in Pulsars
Authors: Slee OB , Bobra AD , Alurkar SK
Published: June 2013

The profiles of 24 pulsars have been measured with the Culgoora circular array at 80 and 160 MHz. The low-frequency profile widths have been combined with most of the published higher frequency widths to generate their pulse-width spectra. We find that:
Coulomb Excitation of the 41+ States of 194,196,198Pt
Authors: Fewell MP , Gyapong GJ , Spear RH
Published: June 2013

Probabilities for the Coulomb excitation of the 4t states of 194,196,198Pt by the backscattering of 4He, 12C and 160 ions are reported. Model-independent values of the matrix elements and (2 t II M(E2) 114t > are extracted. Agreement with previous measurements of these matrix elements is good. Values of {32 and {34 are determined for 194pt and compared with calculations of these quantities.
Acquisition of Powder Diffraction Data with Synchrotron Radiation
Authors: Cox DE , Toby BH , Eddy MM
Published: June 2013

During the past year, a dedicated triple-axis powder diffractometer has been in routine operation at the Brookhaven National Synchrotron Light Source as a user-oriented facility. The diffractometer is designed to allow easy interchange between energy-dispersive and monochromatic beam experiments. In the latter mode of operation, high resolution data have been collected for a variety of samples with the use of the crystal-analyser technique, and in several cases these data sets have been used successfully for structure solution and Rietveld refinement. Several aspects of data acquisition at a synchrotron beam-line are described, and some of the different types of scattering geometry which have been used are discussed. Simple expressions are given for the instrumental resolution function expressed as the angular variation of peak widths for each of these. The peak shapes observed for a reference sample of Si on the present triple-axis instrument are well described by the convolution of Gaussian and Lorentzian functions, and the angular dependence of the Gaussian component is in excellent agreement with the corresponding calculated instrumental function. One of the most important considerations for each type of experiment is the necessary compromise between intensity Ilnd resolution over a wide range of scattering angles, and some of the available options are discussed. In particular, the use of Ge(440) and LiF(400) analyser crystals gives a focussing minimum at relatively high angles (28 ::::: 50� at 1�54 A), a highly desirable feature for Rietveld analysis of complex structures. Absolute intensities from reference samples of Si and Ce02 are calculated for these and several other scattering configurations involving both fiat-plate and capillary geometry to illustrate this compromise.
FLRW Cosmological Models in Lyra's Manifold with Time Dependent Displacement Field
Authors: Beesham A
Published: June 2013

Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological models are derived in Lyra's manifold assuming a time dependent displacement field. The models obtained solve the singularity, entropy and horizon problems which exist in the standard models of cosmology based on Riemannian geometry. The asymptotic behaviour of the models is also examined.
Constructing Large-basis Meson Wavefunctions from Perturbative Cavity Dynamics
Authors: CL Hollenberg Lloyd , HJ McKellar Bruce
Published: June 2013

Amplitudes for the mixing of the meson valence ground state with O(g) states, I qqG}, are calculated using 51/2 quarks and 1+ (TE) gluon wavefunctions from perturbative c cavity dynamics. Bag parameters are obtained for increasing basis size by fitting to 7T-p and� K spectroscopy. The expected self-energy divergence appears to be regulated primarily by the strong coupling approaching zero. The K* and cf> masses are also calculated.
Baryon Structure and QCD: Nucleon Calculations
Authors: Burden CJ , Cahill RT , Praschifka J
Published: June 2013

We present numerical calculations for the structure and mass of the i + nucleon in the chiral limit, using a covariant, QCD based formalism developed previously. The three-body problem of quarks interacting'via gluon exchange is treated as a quark-diquark two-body problem. The nucleon mass and a nucleon-quark-diquark form factor are determined as a function of the one parameter, the diquark form factor normalisation, which can be determined by functional methods. The constituent mass the unpaired quark within the nucleon is estimated to be about 0.44 Gey.
Thermosolutal Instability of a Hall Plasma
Authors: Sharma RC , Sharma KN
Published: June 2013

The last sentence on p. 129 should read: Thus PI > 1, q > 1 and P2 < 1, i.e. K < V < 1] and K' < v, are sufficient conditions for the validity of the principle of exchange of stabilities, as it can be shown under these inequalities that CTI = o.
Uses of Spin-polarised Electrons in Fundamental Electron-Atom Collision Processes and the Analysis of Magnetic Microstructures
Authors: H Kelley Michael
Published: June 2013

Two experimental programs are discussed which exploit the use of polarised electrons for studies of fundamental processes and physical properties. In one program, collisions between spin�polarised electrons and optically pumped sodium atoms provide a very detailed characterisation of the spin-dependent interactions important in low-energy electron-atom collisions. The results of these measurements provide a critical test for the reliability of state-of-the�art electron scattering calculations. In the second program, the spin polarisation of secondary electrons ejected by high� energy electron impact is used to determine the magnetic structure of ferromagnetic materials with very high spatial resolution (-60 nm). This ability to perform such studies with high resolution has been exploited both in studies of the basic magnetic properties of ferromagnetic materials and in studies of how these basic properties affect the magnetic structure and performance of devices used for magnetic information storage.