bluuebunny/crossref_metadata_2025 huggingface dataset:
Boundary-layer Acceleration and Particle Mirroring in Pulsar Magnetospheres
Authors: Burman RR
Published: June 2013

Where the number density of a species becomes very small, inertial development of vorticity occurs; so a magnetospheric zone in which a species is contained must be enclosed by a vortical boundary layer. Where zones of corotating electrons and ions abut, there exists a large local non-corotational electric field, directed so as to force a merging of the electron and ion boundary layers. The poloidalaccelerations and azimuthal drift velocities generated in these layers are estimated here. Ions are accelerated to nonrelativistic or mildly relativistic poloidal speeds, then penetrate into the electron corotation zones where they are centrifugally decelerated as they travel approximately along magnetic field lines. They mirror between points above the stellar surface and the boundary layer, resumably moving to lower magnetic field lines until they reach the star. Electrons are accelerated to poloidal speeds that are relativistic for istances from the axis of rotation exceeding about 1/30 of the radius of the light cylinder. They enter the ion corotation zone where they are further accelerated as they travel approximately along outgoing portions of the closed magnetic field lines, and are then decelerated on ingoing portions. They mirror between the northern and southern boundary layers, presumably moving to lower magnetic field lines until they reach the star. The electrons in the outer parts of the ion.zone are very highly relativistic and emit gamma radiation which, in the case of the Crab pulsar, might create electron-positron pairs.
New Optical Identifications for Weak Sources from the Parkes 2700 MHz Catalogue
Authors: Bolton JG , Trett Jenny , Carignan Claude , Binette Luc
Published: June 2013

Optical identifications are suggested for 122 weak radio sources from the Parkes 2700 MHz catalogue. Optical positions have been measured for the proposed counterparts and for 81 previously suggested identifications.
The Effects of Broadening on the High Temperature Critical Susceptibility Exponent g
Authors: McKenna TJ , Wilson GVH , Campbell SJ , Chaplin DH , Wantenaar GHJ
Published: June 2013

A theoretical study of the effects of a distribution of ordering temperatures Tc on the high temperature critical susceptibility exponent y is described. Analytical and numerical solutions for yare derived for the fitting of broadened susceptibility data to the critical equation X = Xo{(T- Tc)/Tc}-'. Both least squares fitting and Kouvel-Fisher analyses are considered. Using a simple model for magnetically inhomogeneous material it is shown that the inclusion of the internal demagnetizing fields greatly reduces the effect of the broadening upon the deduced critical exponent. Theory is compared with experiment for the critical susceptibility of gadolinium.
A Southern Hemisphere Search for a Nonrandom Component in Cosmic Rays
Authors: Clay RW , Dawson BR
Published: June 2013

A search has been made for a nonrandom component in Southern Hemisphere cosmic radiation with energies greater than ~ 10'4 eV. We find no evidence to correspond to the positive effect reported in the Northern Hemisphere by Bhat et al.
Dicke Narrowing Reduction of the Doppler Contribution to a Line Width
Authors: McMahon DRA
Published: June 2013

In the simplest kinetic models of collisional narrowing or reduction of the Doppler contribution to a spectral line width, the narrowing process is related to the usual diffusion constant of transport theory. Dicke narrowing requires a correlation between the pre- and post-collisional absorber or emitter electric dipole moment. Pressure broadening on the other hand results from at least a partial destruction of this correlation so that in general pressure broadening and Dicke narrowing are statistically dependent on and correlated with each other. It follows that a spectroscopic diffusion constant is required. A classical phase description (which is easily converted to a semiclassical one) is used here to derive a kinetic equation for which the approximate line shape is obtained by It velocity moment method. The spectroscopic diffusion constant closely resembles the Chapman-Enskog first approximation for the diffusion constant but has mixed in an extra function (the memory) which represents the correlation between collision-induced changes of the dipole moment and velocity changes and the correlation between the pre- and post-collision electric dipole moment. Dicke narrowing can be used to obtain information about the line broadening amplitude SB(b, w) for strong velocity-changing collisions. The Galatry ('weak' collision) and 'strong' collision line-shape functions are obtained as different cutoff approximations in the velocity moment analysis. The present analysis, however, is not limited to specifically weak or strong collisions. The two line-shape formulae are shown to be virtually identical sufficiently far from the line centre and at sufficiently high densities. Convenient, approximate analytical formulae for the half-width are obtained using two different definitions.
Large Momentum Transfer Excitation of He(31P) by Electron Impact at 81· 2 eV Incident Energy
Authors: McAdams R , Williams JF
Published: June 2013

This paper reports measurements of helium A and X parameters for electron impact excitation of the 31 P state of helium at an incident energy of 81 �2 e V and at large momentum transfers. Comparison is made with previous 21P results and both sets of results show very similar trends. The data are also compared with a number of theoretical calculations but the agreement is not good.
The Infrared Absorption Spectrum of Water
Authors: Coker DF , Reimers JR , Watts RO
Published: June 2013

A combination of quantum calculations and Monte Carlo methods is used to predict the infrared absorption spectrum of the water monomer, water dimer and the pure liquid. Full quantum calculations using internal coordinates are used to fit three Morse oscillators to the fundamental and overtone vibrations of the water monomer. This intramolecular potential is then combined with an accurate intermolecular surface to calculate the dimer spectrum from a normal mode analysis and from classical trajectory studies. The liquid state spectrum is obtained using a Monte Carlo simulation program together with a sequence of normal mode analyses of representative molecular configurations. Results are in good agreement with available experimental data suggesting that the potential energy surfaces used are reasonably accurate.
A Hybrid Model for Charmed Meson Decays
Authors: M Gorman Richard , HJ McKellar Bruce
Published: June 2013

Two-body decays of the charmed mesons to both PP and PV final states are discussed, employing an effective Lagrangian formalism. We show that a hybrid model combining the pole model and the c-quark decay model provides a reasonable description of the amplitudes for these processes.
The Extremely Large Effective Coulomb Matrix Element of 66Ge?66Ga
Authors: Yap CT , Saw EL
Published: June 2013

A calculation using Nilsson wavefunctions and an effective one-body spheroidal Coulomb potential yields extremely large values for the Coulomb matrix element even for relatively small deformations of 66Ge.
Removal of Channelled Spectra Signatures in Fourier Spectroscopy
Authors: Grant KJ , Fisher P , Kosaka M , Martin AD
Published: June 2013

The presence of a plane, parallel-sided dielectric component in the optical path produces channeled spectra or signatures in conventional or Fourier transform spectroscopy respectively. These features are generally undesirable and a method of removing them based on scaling the zero path signature of the interferogram is described. Spectroscopic information concealed by the signatures is left intact. The method is applied to signatures arising from the diamond window of a Golay detector and the results presented for both the interferograms and the corresponding spectra.
Drift and Diffusion of Electrons in an Atomic Gas between Closely Spaced Electrodes. I. Theory for Elastic Electron?Atom Collisions
Authors: McMahon DRA
Published: June 2013

The solution of the two-term approximation for the Boltzmann equation for electron drift and diffusion in an atomic gas between closely spaced electrodes has been obtained with the neglect of energy losses by elastic collisions. Although the omission of elastic collision energy losses (equivalent to using an infinite atomic mass) may appear to be a drastic oversimplification it does approximate the real physical situation where the cathode and anode are separated by a distance less than the thickness of the so-called boundary layer. The theory may be used as a guide in developing future, more accurate analytic theories of electron swarms between closely spaced electrodes. The present work has some special advantages however not so far achieved with previous analytic work on electron transport in the boundary layer region. There is no restriction to special model momentum transfer cross sections and the results can be written in easily interpreted analytic forms. The effects of inelastic collisions, the subject of a second paper, can also be included. In an attempt to obtain a better physical understanding of boundary effects, the present paper studies the influence of electron reflections from the electrode surfaces. Expressions are obtained which eliminate the electrode sensitive terms and relate experimentally measurable quantities to the momentum transfer cross section alone.
Relativistic Corrections of Closed-shell Atomic Systems
Authors: Glass R
Published: June 2013

Analytical expressions for the relativistic energy associated with close,d-sheII atomic systems have been given by Hartmann and Clementi (1964). We derive a new set of analytical expressions and conclude that those of Hartmann and Clementi are in error.
Estimation of Single Crystal Integrated X-ray Intensity within a Designated (D?, D2?) Domain
Authors: McL Mathieson A
Published: June 2013

It is shown that measurement of the integrated intensity of a Bragg X-ray reflection within a precisely defined area of the (Aw, A2() distribution (Mathieson 1982a) is possible using a standard scintillation detector. The method involves an aperture system in front of the detector, consisting of two halves which are independently controlled so that both the width and position of the aperture are variable and can follow the A2() boundaries of the sections of any specified convex domain in (Aw, A2() space, as the specimen crystal steps in Aw. By taking account of the dispersion of the wavelength, crystal mosaicity and source components, the method can (a) exclude those extraneous contributions which, particularly at low () angles, constitute a major error source with conventional fixed-aperture procedures and (b) obviate the so-called truncation error at high () angles. This boundary-following method therefore provides, by a simple instrumental operation, a much closer estimate of the true integrated intensity of a Bragg reflection from a small single crystal than is feasible with the use of a fixed aperture. Once the main parameters of the experiment are determined, the procedure requires no greater expenditure of time than the traditional fixed-aperture method.
Drift Velocity of Electrons in Nitrogen?Argon Mixtures
Authors: Haddad GN
Published: June 2013

Electron-drift velocities have been measured in mixtures of 0�1 %, 1 % and 5 % nitrogen in argon at 293 K. A modification of the drift-tube system, which provides semi-automatic control and data collection, is described. Agreement with some previous work is very good. The uncertainty of the present measurements is estimated to be less than 1 %.
Survey of OH Masers at 1665 MHz. II. Galactic Longitude 340o to the Galactic Centre
Authors: Caswell JL , Haynes RF
Published: June 2013

The galactic plane from longitude 340� through the galactic centre to longitude + 2� has been searched for OH on the 1665 MHz transition. Forty-nine OH maser emission sources were detected and these have now been studied on all four OH ground-state transitions. Most of the masers are associated with regions of star formation (type I) while three may be examples of late-type stars (type II OH/IR) with unusually strong main-line emission
Structure of a Sequence of Two Zone Polytropic Stellar Models with Indices 0 and 1
Authors: Murphy JO
Published: June 2013

The structure and physical properties of a sequence of two zone polytropic stellar models, based on E-type composite analytical solutions of the Lane-Emden equation for indices n = 0 and 1, have been determined. The resulting models are characterized by an inner zone of constant density, corresponding to the n = 0 component, and a relatively small envelope with a steep polytropic density gradient and index n = 1. At the surface of these near uniform density composite configurations the physically significant condition p = 0 is always satisfied, a condition which is not fulfilled by the complete poly trope of index n = O. In each model the surface corresponds to the first zero of the associated composite function, which in turn is given by one of the higher order zeros of the E solution of the Lane-Emden equation for n = 1. The radial pulsational properties of these low central condensation type models have also been investigated with the relative amplitudes of radial displacement and density variation given as a function of radial distance for the first six modes of some selected models. Overall, these results establish that the radial displacement amplitudes are only significant in the n = 1 outer layer and accordingly the pulsations can be classified as essentially surface phenomena
A Simple Microcomputer-controlled Calorimeter: the Heat Capacity of Copper, Invar and RbNiCl3 in the Range 2?20 K
Authors: Collocott SJ
Published: June 2013

A simple inexpensive microcomputer has been used to control an adiabatic pulse-type calorimeter. The data acquisition control system incorporates a Rockwell AIM65 microcomputer to control all aspects of the thermometry and the injection of the heat pulse into the sample. Details of the hardware and software requirements are discussed, including the interface of the system with a host computer that uses the UNIX operating system. The performance of the apparatus was evaluated by measuring the heat capacity of 1965 Calorimetry Conference copper between 2 and 20 K. The results show a total r.m.s. deviation of less than 0�4 % and agree well with the copper reference equation (r.m.s. deviation 0�4 %). Measurements are also presented of the heat capacity of Invar (Nilo 36) and RbNiCI3 over the same temperature range. In the case of RbNiCh the heat capacity anomaly associated with the paramagnetic-anti ferromagnetic transition is observed at 11�1 K.
Electron Impact Excitation Cross Sections for B III
Authors: Ganas PS , Aryafar M , Gately LP
Published: June 2013

A realistic analytical central potential with two adjustable parameters is used to generate wavefunctions for the ground and excited states of doubly ionized boron. Generalized oscillator strengths and integrated cross sections from threshold up to 5 keY are calculated in the Born approximation for 2s-ns, 2s-np and 2s-nd excitations. Convenient analytic formulae for the cross sections are presented.
Correlations, Long Range Order and Dimensionality
Authors: Buckingham MJ
Published: June 2013

After a retrospective look at the nature of correlations in the case of the helium A transition, we consider long range correlations and their information content for critical phenomena in general. Separation of the statistical from the geometric information leads to the resolution of a long-standing dilemma concerning the dimensionality dependence of the hyper-scaling relations. The hyper-scaling inequalities are the result of the significant correlations suffering a re-arrangement when a regular contribution dominates the singular part of the free energy. The inequalities can each be replaced by a pair of equalities. This resolution has a bearing on the special place of four dimensions as the origin for the e-expansion technique of the renormalization group approach.
Power Series Expansion of the Mie Scattering Phase Function
Authors: A Box Michael
Published: June 2013

We develop power series expansions for both the Mie theory scattering amplitudes and the scattering phase matrix elements in terms of the variable s = sin2W, where () is the scattering angle. It is easily seen that s is the natural variable for such expansions. These expansions should prove particularly useful whenever the forward diffraction peak, rather than the entire phase function, is of primary interest. Possible applications include the analysis of solar aureole data and the modelling of laser beam propagation in fogs and dust clouds.
Model Calculations of Negative Differential Conductivity in Gases
Authors: Petrovic ZLj , Crompton RW , Haddad GN
Published: June 2013

Negative differential conductivity in gases has been studied using simple models of elastic and inelastic collision cross sections for electron scattering. The use of such models has demonstrated features of the cross sections that lead to the phenomenon, and shown that it can occur without a Ramsauer–Townsend minimum (and even without a sharply rising momentum-transfer cross section) or a special combination of inelastic cross sections.
Observation of an Excess of Cosmic Ray Showers from the Direction of Centaurus A
Authors: Clay RW , Gerhardy PR , Liebing DF
Published: June 2013

An analysis of recent data from the Adelaide cosmic ray shower array suggests that an excess of events may have been observed to come from the general direction of Centaurus A. These data are presented and discussed together with directional data from other previous experiments.
Rotational Motion of the NH+4 Ion in Ammonium Chloride
Authors: Pandey Sadhana , Trikha SK
Published: June 2013

The rotational motion of the ammonium ion in NH4CI at low temperature under the influence of its nearest neighbours has been studied using a computer simulation technique. The Lennard Jones potential is used as the representative interaction between NHt and CI-. Three values of the time increment At occurring in the algorithm equation are taken to illustrate the three-dimensional effect on the rotational dynamics of the NH: ion. In each case we notice a well defined transition gap around = 1�25 separating phases II and III which are known from the literature. The libration frequency of the ammonium ion is found to be 1"0; 170 em-1, corresponding to the transition temperature of 242 K, which is in agreement with the Raman spectra study by Couzi et af. (1973).
Two Procedures for Phase Estimation from Visibility Magnitudes
Authors: Sault RJ
Published: June 2013

Two procedures, which retrieve phase information from magnitude data, are examined. These procedures, one due to Bates, Fright and Garden and the other due to Fienup, are firstly reviewed, and then numerical results are presented to quantify the effectiveness of the algorithms. Some areas where Bates' algorithm could be further refined are suggested.
Nocturnal Sporadic-E Activity at Two Southern Hemisphere Stations over Three Solar Cycles
Authors: Baggaley WJ
Published: June 2013

Analyses are presented of monthly values of the occurrence of the ionospheric parameters j~ E; and foE; for the South Pacific stations Christchurch and Rarotonga over three complete solar cycles. For each station both pre-midnight and post-midnight data show seasonal variations similar to daytime with the high latitude station showing a winter enhancement. Data fluctuations of scales longer than a year are very pronounced compared with variations in other ionospheric parameters. No correlations exist between any of the data sets and either the sunspot number Rz or geomagnetic index. Long-term variations in fi.E, and fo E; are uncorrelated at a particular station.
Structural Changes in Ionosonde Es over Three Solar Cycles
Authors: Baggaley WJ
Published: June 2013

A survey over 37 years of the ionization structure of temperate latitude daytime sporadic-E, inferred from ionogram characteristics, shows a close association between solar cycle and the type of structure. Sporadic-E demonstrates a high degree of scattering near sunspot minimum.
Variational Approach to the Calculation of the Binding Energy of 31Si
Authors: Ahsan MH , Ali S
Published: June 2013

The double hypernucleus llsi has been considered as a three-body system A-A-29Si and its binding energy calculated by a variational method using a trial wavefunction of the form F(rCl) F(rC2) G(r12), where the r are interparticle triangular coordinates and F and G are of the form z exp( - rxr 2) + exp( - pr2 ). These wavefunctions allow the description of strong A-A spatial correlations which are found to be quite significant. The parameters z, rx, p for the two-body wavefunctions F and G are obtained by a variational procedure in order to find the binding energies of the two-body systems A_29Si and A-A. The parameters of the A-A wavefunction are adjusted so as to produce just a zero-energy A-A system. For the A _ 29Si system the interaction potential between A and 29Si is generated by folding a gaussian A-N potential into the density distribution of 29Si. Parameters for the A_29Si system are used in the three-body calculation, but those for the A-A system are kept free in the three-body variational calculation. In the first stage, our calculated value of the binding energy is 41� 54 MeV, where we have used a gaussian A-A interaction having a volume integral of 610'8 MeVfm3 ? This volume integral is calculated from the two-body A-A system. In the second stage we have taken the volume integral as a free parameter also, and calculated the binding energy of j~Si to be 39�7 MeV, for a volume integral of 356� 5 MeVfm3 for the A-A potential. This value is compared with the experimental value of 38�2�6�3 MeV found by Mondal et al. (1975). The dependence of the binding energy on the depth of the A-A interaction has also been investigated.
Dead Time Correction for a Position Sensitive Detecto
Authors: Brown TC , Mackenzie JK
Published: June 2013

The dead time of some position sensitive detectors is determined by the arrangement in time of the totality of incoming events, irrespective of the position channel to which each event may be assigned. If the arrangement of events in position is statistically independent of their arrangement in time, the ratios of the means for the different position channels are unaffected by dead time and all channels need correction by the same factor, determined solely by the combined rate for all channels. Expressions for the variance of the individual counts in each channel are given for Type I counters. A symmetric uncertainty in the allocation of each event to its proper channel is considered and has no effect in a first approximation.
A Neutron Spectrometer with a Two-dimensional Detector for Time-resolved Studies
Authors: Schoenborn BP , Saxena AM , Stamm M , Dimmler G , Radeka V
Published: June 2013

An intermediate resolution neutron spectrometer for collecting diffraction data with the range Q = 0�01-3�0 � has been built for analysing the structural organization of membranes, polymers and other molecular aggregates. This spectrometer has a position-sensitive detector with a capability for time-resolved data collection which may be used to study conformational changes in dynamical systems. A double multilayer monochromator assembly is used to monochromate neutrons. Operating wavelehgths of the spectrometer will be from 2 to 5 �, and the wavelength bandwidth (??/?) can be adjusted within the 1%-8% range.
Evaluation of Core Correlation Effects in the 4s4p1P0 State of Calcium
Authors: Glass R
Published: June 2013

In this paper two different approaches are used to study core correlation effects in the 3p64s4p I pO state of calcium. We show that the number of relevant configurational functions in the configuration interaction expansion can be reduced by determining the core correlation functions prior to the valence correlation functions. We also show that core correlation effects of the form 3p2 ~ nP can be represented in the configuration interaction expansion by including configurational functions of the type 3p4(S L) nP(S L){ IS 14s4p in the expansion.
The Effect of the Angular Dependence of Sputtering in Fusion Reactors
Authors: Cook JL , Rose EK
Published: June 2013

Recent work on the angular distribution of sputtering yields is reviewed and then compared with experiment. The most probable angular distribution law is evaluated from experiment. By averaging over an incident Maxwellian spectrum of ions, it is shown that there is considerable enhancement over the isotropic case, which would increase the total sputtering at the walls or limiters of fusion reactors over the example of an isotropic angular distribution.
Calculation of the 13N(p, ?)14O Cross Section at Low Energies
Authors: Barker FC
Published: June 2013

R-matrix formulae are used to calculate the 13N(p, ?) 140 cross section in the energy region of astrophysical interest. Values of the R-matrix parameters are determined by fitting experimental data in 14C and 14N as well as 140, and by making use of shell model calculations where necessary. With the presently available data, there is considerable uncertainty in the predicted cross section, but this could be reduced appreciably by a measurement of the lifetime of the first excited state of 14C. With the preferred channel radius of about 5 fm, the predicted cross section is lower than those found in two previous calculations, which are discussed in some detail.
Computer Simulation Studies of the Phase Transition in Compressible Deuteroammonium Chloride
Authors: Pandey Sadhana , Trikha SK
Published: June 2013

The effects of pressure on the dynamical behaviour of an ND t ion near the A transition under the influence of its nearest neighbours in deuteroammonium chloride have been studied by using the computer simulation technique. The well-known Lennard Jones (6-12) potential is used as the representative interaction between ND t and CI-. The libration frequency of the ND t ion is estimated to be approximately 130 and 145 cm -1 at pressures of 1 atm and 3 kbar respectively.
Contributions by RG Giovanelli to Solar Instrumentation
Authors: M Beckers Jacques
Published: June 2013

R. G. Giovanelli and his co-workers at CSIRO have contributed in a major way to the renewal in solar instrumentation which has occurred since the nineteen fifties. I review here some of their contributions.
Magnetohydrodynamic Tube Waves: Waves in Fibrils
Authors: Cally PS
Published: June 2013

A discussion of waves in magnetic flux tubes imbedded in magnetic unstratified surroundings is given. Seven types of non-leaky wave are identified. Many more leaky waves, tube oscillations which drive waves in the external medium and thereby lose energy to it, are also found. The particular example of longitudinal and transverse oscillations in chromospheric fibrils is examined in detail.
Dynamic Time Dependent Hexagonal Magnetoconvection
Authors: Lopez JM , Murphy JO
Published: June 2013

The time dependence of the single mode hexagonal magnetoconvective system has been investigated numerically at high Rayleigh number. It is established that, in certain parameter ranges, the system has oscillatory solutions which not only have a periodic nature, but also develop into chaotic and intermittent solutions. Further, the system generates nonzero mean kinetic and magnetic helicity together with substantial magnetic field amplification. These features are shown to be maintained in time without any externally imposed rotation of the system.
Evidence for a Common Magnetic Driver for Flares and Quiescent Coronae/Chromospheres
Authors: Skumanich A
Published: June 2013

The mean power and rate of optical flares in dMe stars are found to be correlated with their quiet coronal X-ray luminosity. The mean flare luminosity in the photometric V-band appears to scale linearly with the X-ray luminosity with a slope of 0�04. This coincidence suggests that quiet and flare activity in coronae/chromospheres may be related by one and the same flaring mechanism. We propose that 'quiet' activity is due to microflares-a low yield but high frequency continuation of flares.
Experimental Determination of the Imaging Properties of a 200 kV Electron Microscope
Authors: Glanvill SR , Moodie AF , Whitfield HJ , Wilson IJ
Published: June 2013

Optical transforms from a through focal series of images of amorphous films of Ge were used to measure the spatial frequencies of maximum and minimum phase contrast of a specific 200 kV lEOL electron microscope. This information was used to determine precise values for the spherical aberration coefficient and defect of focus. Under the appropriate conditions of lens excitation the spherical aberration coefficient was found to be as low as 0�94 mm. Other image defects revealed with great precision were associated with astigmatism, beam divergence and specimen drift in the microscope stage. Quantitative examples illustrating these effects are discussed.
Conduction Electron Scattering in Alloys
Authors: Rossiter PL
Published: June 2013

The aim of this review is to present a simple physical picture which shows how the electrical resistivity of a system depends upon the spatial extent and lifetime of the scattering disturbance measured in relation to the conduction electron mean free path and relaxation time. The contribution from spin fluctuations associated with isolated magnetic impurities is discussed on the basis of this model and it is shown that at temperatures below the characteristic spin fluctuation temperature the impurity acts as though it were nonmagnetic. Some results are given for both 'Kondo' (Anderson) and exchange enhanced (Wolfi) systems. Spin glasses are also discussed and the resistivity behaviour is shown to result from a competition between the RKKY interaction and spin fluctuation effects. Ordered magnetic clusters are shown to be static for periods comparable with the conduction electron relaxation time, so that there is no resistivity anomaly expected at the superparamagnetic blocking temperature. The observed temperature dependence of the resistivity then follows simply from the change in magnetic correlations within the cluster.
Electronic Structure of the Principal Uranium Centre in Alkali Fluorides
Authors: Runciman WA , Srinivasan B , Saebo S
Published: June 2013

Fluorescent centres are formed when hexavalent uranium is incorporated into lithium fluoride and sodium fluoride in an oxygen atmosphere. The principal centre is believed to consist of a UOsF group. Calculations have been made of the electronic structure of this centre assuming that the excited states are due to charge transfer transitions. Different models are considered and fitting procedures used to find parameters yielding good agreement with the energy levels and 9 values of the seven lowest excited states of the centre in sodium fluoride. A similar model is believed to be applicable to the principal centre in lithium fluoride.
The Analysis and Understanding of Ionisation Phenomena: Ab initio Molecular Wavefunctions
Authors: S Bagus Paul , J Nelin Constance , Hermann Klaus
Published: June 2013

Two distinctly different kinds of information can be obtained from ab initio wavefunctions. The v~lue of observables can be computed, quite accurately for relatively small systems, but this only complements experiment. However, the analysis and interpretation of wavefunctions can lead to conceptual understanding of the significance of measured values. Ab initio wavefunctions are essential because they provide a unique and sound basis for determining the importance of various mechanisms. Three cases where this analysis has lead to new understanding will be described. The shift to higher binding energy (BE) of the 50" orbital relative to the hr orbital for chemisorbed CO is shown to be dominantly an electrostatic effect; it does not indicate the chemical bonding. The shift of core level BEs with the size of metal clusters is shown to be an initial state effect which depends on the coordination of the ionised atom; differential final state effects may not be large. The satellite structure for core ionisation of the NO dimer is due to both intra- and inter-unit screening. In all� these cases, the correct mechanisms could only be established with accurate ab initio wavefunctions.
Collisions in Strong Magnetic Fields
Authors: C Storey Michelle , Melrose DB
Published: June 2013

Exact cross sections for electron-electron collisions and electron-proton collisions in a superstrong magnetic field are derived using the QED formalism developed by Melrose and Parle. The results are compared with those of Langer who used a different QED formalism. The intended application is to collision processes in the accretion columns above neutron stars where magnetic fields of order 109 T are thought to be present. The particular case of electrons initially in their ground states, with one final electron in an excited state is described in detail; this process is thought to be the primary source of photons in X-ray pulsars, through subsequent cyclotron emission.
The Formation of the Universe from Rotating Superstrings
Authors: Tassie LJ
Published: June 2013

The examination of the masses and angular momenta of a wide variety of astronomical objects, ranging from planets to clusters of galaxies, suggests that astronomical objects were originally formed from rotating superstring. Each piece of rotating string breaks into smaller pieces with masses corresponding to smaller astronomical objects. One possibility is that the Universe starts as one piece of rotating superstring.
Proton Induced X-ray Emission for Measurement of Bromine in Micro Quantities of Human Blood Plasma
Authors: J Hay Halcro , B Cheek Donald
Published: June 2013

Studies have been made with proton induced X-ray emission to measure bromine in human blood plasma, and thereby estimate the extracellular fluid volume which is a determinant of biological importance. With careful attention to sample preparation, the method is precise. Since only very small amounts (less than O� 1 ml) of material are needed, the technique is applicable to the newborn and to small mammals.
Survey of OH Masers at 1665 MHz. III. Galactic Longitudes 233° to 326°
Authors: Caswell JL , Haynes RF
Published: June 2013

We have searched the galactic plane from longitude 233� to 326� for OH emission on the 1665 MHz transition. Between longitudes 270� and 326�, where the survey zone was a uniformly sampled grid, we detected 35 OH maser sources, including 24 new ones; most are of the Type I variety that delineates sites of current star formation, and many of the sites are young, with no well-developed HII regions in the vicinity. By combining the present results with those of earlier surveys Oongitudes 326� ? 360� ? 2�: Parts I and II) we have improved on previous estimates of the galactic distribution of these masers.
A Formal Time-domain Approach to Cold Magnetised Plasmas
Authors: Weiglhofer Werner
Published: June 2013

Representations of the electromagnetic and the average velocity field for a cold magnetised plasma are derived in terms of scalar potential functions. These Hertz potentials are solutions of a coupled system of integro-differential equations of second Qrder. Different from other approaches, the analysis is carried out in the time domain and is therefore especially suited for the investigation of transient wave phenomena. Furthermore, the dielectric tensor operator of the plasma is derived. Mter solving the system of integro-differential equations for a special limiting case, the applicability of the method presented is demonstrated and generalisations are discussed.
Generalised Least-squares Determination of Triaxial Stress States by X-ray Diffraction and the Associated Errors
Authors: Winholtz RA , Cohen JB
Published: June 2013

The determination of residual stresses via X-ray diffraction is briefly reviewed, with particular emphasis on the triaxial stress state. A new method is proposed for determining the general stress tensor, which considerably reduces the variances of the stresses due to counting statistics and gradients. The procedure involves a generalised least-squares solution of strains measured at various tilts of the X-ray beam to the sample, and a new set of tilts is recommended to minimise these errors.
Use of Extinction Corrections in Neutron Diffraction Experiments
Authors: Delapalme A
Published: June 2013

The study of extinction by neutrons reveals many features of the extinction problem: theory and practical cases, polarised and unpolarised neutron cases. Special attention is given to the usual extinction corrections for neutron diffraction experiments, showing the relative importance of structure factor, wavelength, Lorentz factor, mosaic and the path of neutrons through the crystal. Two problems are reviewed: (a) how to detect the presence of extinction in both cases of a single crystal experiment with polarised and unpolarised neutrons; and (b) after experimental evidence for extinction in a neutron diffraction experiment, how to follow a reliable way to correct the neutron diffraction data in both cases of polarised and unpolarised neutron experiments. Some examples are given.
Accurate Measurement of Powder Diffraction Intensities Using Synchrotron Radiation
Authors: Parrish W , Hart M
Published: June 2013

This paper reviews the advantages of synchrotron radiation for obtaining accurate values of the integrated intensities of powder samples for crystal structure refinement. The higher accuracy than conventional X-ray tube focusing methods results from the parallel beam geometry which has a symmetrical constant instrument function, higher intensity and resolution and easy wavelength selectivity. The importance of specimen preparation and the profile fitting function are discussed.
Redetermination of Absolute Structure Factors for Silicon at Room and Liquid Nitrogen Temperatures
Authors: Cummings S , Hart M
Published: June 2013

Many new determinations of silicon structure factors have been made in the last few years providing confidence in dynamical diffraction methods and challenging the basis of available theories. The first analysis of experiments done in the early 1970s (Aldred and Hart 1973) has been repeatedly compared with theories and more recent experiments. A number of minor problems have come to light, for example, the crucial need to detect strain gradients and small changes in the accepted values of some parameters. Fortunately, the raw data was published by Aldred and we have reanalysed these experiments, making corrections for strain gradients. These new results still comprise the only low temperature high precision data on silicon, which is an important feature since it is becoming increasingly clear that anharmonic effects are insufficiently well measured in silicon compared with other features of the electron density.
Measurement of Thermal Diffuse Scattering Using Pulsed Neutron Diffraction
Authors: Willis BTM
Published: June 2013

Collective excitations in crystals can be examined with neutrons by means of the so-called 'diffraction method', without carrying out an energy analysis of the inelastically scattered neutrons. For studying thermal diffuse scattering (I'DS) from acoustic phonons, it is particularly advantageous to employ a white source of pulsed neutrons instead of a monochromatic source of reactor neutrons. Provided that the neutron velocity is less than the sound velocity in the crystal, each reciprocal-lattice point observed in backscattering Laue geometry is associated with a wavelength window within which TDS is forbidden. The edges of the window are readily measured to give the sound velocity as a function of the direction of propagation.
Thermal Expansion of Willemite, Zn2SiO4
Authors: White GK , Roberts RB
Published: June 2013

The linear thermal expansion of a natural crystal of willemite (Zn2Si04) has been measured parallel and normal to the hexagonal axis from 2 to 1200 K. The linear coefficient a" is negative below 150 K and al is negative below room temperature. The Grtineisen parameter 'Y is about 0�5 at 1000 K and falls to less than - 1 below 60 K.
Delayed Alpha Spectra from the Beta Decay of 8Li and 8B
Authors: Barker FC
Published: June 2013

Many-level R-matrix fits are made to the ()(-()( scattering d-wave phase shift and to ()(-spectra from BLi and BB ,8-decay measured by Wilkinson and Alburger (1971). With the requirement that the parameter values are the same in the fits to the phase shift and the ()(-spectra data, the best overall fits are obtained for a channel radius of about 6�5 fm, implying a broad 2+ intruder state of BBe at about 9 MeV. There is satisfactory agreement between the Gamow-Teller matrix elements extracted from the fits and shell model values.
Measurement of Reduced Electric Octupole Transition Probabilities, B(E3; 01??..31), for 118,120,122Sn
Authors: Spear RH , Baxter AM , Burnett SM , MiIler CL
Published: June 2013

Values of reduced electric octupole transition probabilities, B(E3; ot -31), for the nuclides llB,120,122Sn have been determined using Coulomb excitation with 12C projectiles. The results are in good agreement with shell-model calculations made without introducing effective charges but involving core excitations. Values for B(E2; ot -2t) are also presented.
Infrared Absorption and Reflection Spectra of Crystalline TCNQ Salts
Authors: T Oza Ajay
Published: June 2013

The polarised absorption and reflectance spectra of the three TCNQ salts pyridinium (TCNQh, triethylammonium (TCNQh and thermally damaged quinolinium (TCNQh indicate that the absorption features are governed by reflection characteristics. The maximum reflectance curve shows a broad minimum which corresponds to a negative dip in the real part of the dielectric constant and a broad maximum in the imaginary part, as calculated using a Kramers-Kronig
Cathode Region of a Steady-state Townsend Discharge in Nitrogen
Authors: Kelly LJ , Brennan MJ , Wedding AB
Published: June 2013

The photon flux technique has been used to study the cathode region of a steady-state Townsend discharge. Spatial variations in the radiation emitted from the C3fIu and B2.r~ states of molecular nitrogen were etected in the vicinity of the cathode for EIN"" 331 and 555 Td. In particular, the second positive emission at 337�1 nm is similar to the Holst-Oosterhuis layers observed in rare gas discharges.
Cosmic Ray Anisotropy below 1015 eV
Authors: Bird DJ , Clay RW , Edwards PG
Published: June 2013

Measurements have been made of the cosmic ray anisotropy at 35�S with a sea-level unshielded air shower array sensitive primarily to the proton component of the cosmic ray beam with energies between 1014 and 3x101S eV. The first harmonic of the anisotropy was found to have an amplitude of O� 34(�0 �09)% at a phase of 318(�18)o.
Preparation and Microstructural Investigation of the High?Tc Superconductor Pb2Sr2Y0.5Ca0.5Cu308
Authors: White TJ , Barnea Z , Goodman P , Jensen DG
Published: June 2013

Simple conditions for the preparation of the high-Tc superconductor Pb2Sr2Yo-sCao�sCu308+o in single phase are given. High resolution electron microscope studies of this material confirm the basic orthorhombic structure having Cmmm symmetry. Overlaying this structure is a perturbation due to random displacements of Pb from the ideal square-symmetric Sites, attributed to a randomness in oxygen sub-stoichiometry. This and the absence of superstructure ordering appears to characterise the uperconducting form of this compound.
Measurements of the Radio Refractive Index Structure Parameter C2n with a Microwave Refractometer in Tropical Latitudes
Authors: Sarma SBSS , Pasricha PK
Published: June 2013

The spatial and temporal variations of the radio refractive index lead to scattering of electromagnetic energy. Modern communication systems are subject to vagaries of the turbulence due to the radio refractive index fluctuations. Vertical esolution of radiosondes is insufficient to resolve the structures of clear air turbulence in the atmosphere. In a tropical ountry like India, aircraft measurements of radio refractive index fluctuations have been non-existent. refractivity, has a lower value in local winter than in summer.
Introduction
Authors: Freeman KC
Published: June 2013

A workshop on 'The Early Universe' was held at Mount Stromlo Observatory, near Canberra, in June 1989. The discussion topics included a wide range of theoretical and observational aspects of the astrophysics of the early universe, from the origin of primordial fluctuations to the properties of high red shift galaxies. This issue of the Australian Journal of Physics presents most of the formal papers given by astrophysicists from the USSR and Australia at this workshop
The Epoch of Galaxy Formation
Authors: Quinn PJ
Published: June 2013

Observations of merging and active galaxies at red shifts less than one suggest that galaxy formation is an ongoing process. Cosmological N�body models and analytiC estimates of the collapse times of large galaxies suggest that the first systems to form .probably did so at redshifts less than 4. The theoretical picture that leads to these estimates of the beginning of the formation epoch may be seriously in error if new observations of high redshift galaxies reveal a pre�existing old stellar population.
Formation of the Structure of the Universe: Observational Aspects
Authors: Einasto Jaan
Published: June 2013

A review of recent developments in the study of the structure of the universe is given. We focus on two problems: the fractal description of the universe, and on observational constraints on the bias in galaxy formation.
Self-focusing of Laser Beams in Cadmium Manganese Telluride Cd0.4Mn0.6Te
Authors: Dai XD , Ito Y , Ja YH
Published: June 2013

Laser beam induced self-focusing in a relatively new diluted magnetic semiconductor cadmium manganese telluride (Cdo.4Mno.6Te) has been observed. We found that a thermally-induced change in nonlinear refractive index is the main mechanism responsible for the self-focusing effect. The nonlinear refractive index has been determined using experimental results.
Variational Solutions of the Hubbard Model for the bcc Lattice
Authors: Villet CM , Steeb W-H
Published: June 2013

A variational method is used to find approximative solutions of the Hubbard model for the ground state of the bcc lattice in the weak and strong coupling limits. The neutral case (a half-filled band) is found to be antiferromagnetic for all values of the coupling constant. However, for other choices of the band� filling second phase transitions between different magnetic structures are found if the coupling constant is varied.
Applications of Lasers to Collision Studies
Authors: MacGillivray WR , Standage MC
Published: June 2013

A review is presented of theoretical and experimental aspects of the application of lasers to the field of electron-atom collision physics. Experimental techniques are briefly reviewed and various theoretical treatments of the laser-atom interaction are dealt with in some detail.