bluuebunny/crossref_metadata_2025 huggingface dataset:
A Guide to Rotations in Quantum Mechanics
Authors: A Morrison Michael , A Parker Gregory
Published: June 2013

To lay a foundation for the study and use of rotation operators in graduate quantum mechanics and in research, a thorough discussion is presented of rotations in Euclidean three space (R3 ) and of their effect on kets in the Hilbert space of a single particle. The Wigner D-matrices are obtained and used to rotate spherical harmonics. An extensive ready-reference appendix of the properties of these matrices, expressed in a consistent notation, is provided. Careful attention is paid throughout to various conventions (e.g. active versus passive viewpoints) that are used in the literature.
A Bosonisation of QCD and Realisations of Chiral Symmetry
Authors: Roberts CD , Cahill RT
Published: June 2013

We employ the functional integral formalism to study quantum chromodynamics (QCD) with Nf quarks of zero bare mass. In addition to local SU(Nc) colour symmetry, this theory possesses exact global G = UdNf)@UR(Nf) chiral symmetry. We obtain an exact bilocal Bose field representation of the generating functional which, as we prove after establishing the manner in which the bilocal fields transform under G, preserves the global chiral symmetry. We demonstrate how a local Bose field representation of the generating functional may be obtained from the bilocal bosonisation. This provides a direct link between QCD and low energy meson phenomenological models. We utilise the bilocal bosonisation in the study of the dynamical breakdown of the global chiral symmetry group G. We derive the vacuum field equation from the exact bilocal Bose field effective action and discuss two alternative solutions: one corresponding to a Wigner-Weyl realisation of the global symmetry group G in which the vacuum configuration is invariant under G; the other to a mixed realisation in which the vacuum manifold is the coset space G/H = U A(Nf ), where H = Uv(Nf ) is a subgroup of G.
Non-hydrodynamic Contributions to the End Effects in Time of Flight Swarm Experiments
Authors: K Standish Russell
Published: June 2013

The hydrodynamic part of the distribution function of a swarm is separated from its nonhydrodynamic part using a projection operator, leading to an explicit expression for the timedependent transport coefficients. These are then related to a time of flight experiment. The contribution from non-hydrodynamic effects to the measured drift velocity is shown to be a power series in 11 d, where d is the drift length. A calculation based on an exactly soluble Fokker-Planck model shows that the correction to mobility measurements of lithium ions in helium due to non-hydrodynamic effects is of the same order of magnitude as those observed experimentally.
Stability of mKdV?KdV Waves
Authors: Murawski K , Infeld E
Published: June 2013

We consider a combination of modified Korteweg-de Vries waves and ordinary Kortewegde Vries waves, known as mKdV-KdV waves. The Infeld-Rowlands method is developed to study the instability of mKdV-KdV waves in the limit of long wavelength perturbations.
Profile Analysis for Microcrystalline Properties by the Fourier and Other Methods
Authors: Langford JI , Delhez R , de Keijser ThH , Mittemeijer EJ
Published: June 2013

In the 1960s the Fourier and variance methods superseded the use of the FWHM and integral breadth in detailed studies of microcrystalline properties. Provided that due allowance is made in the analysis for systematic errors, particularly the effects of truncation of diffraction line profiles at a finite range, these remain the best methods for characterising crystallite size and shape, microstrains and other imperfections in cases where accuracy is important. However, the application of the Fourier, variance and related methods in general requires that the diffraction lines are well resolved and it is thus restricted to materials with high symmetry or which exhibit a high degree of preferred orientation. Most materials, on the other hand, including many of technological importance, have complex patterns with severe overlapping of peaks. The introduction of pattern-decomposition methods, whereby a suitable model is fitted to the total diffraction pattern to give profile parameters for individual lines, means that microcrystalline properties can now be studied for any crystalline material or mixture of substances. The use of the FWHM and integral breadth has been given a new lease of life; though the information is less detailed than is given by the Fourier and variance methods and systematic errors are in general greater, self-consistent estimates of crystallite size and microstrains are obtained.
Size and Strain Parameters from Peak Profiles: Sense and Nonsense
Authors: Delhez R , de Keijser ThR , Mittemeijer EJ , Langford JI
Published: June 2013

In principle the analysis of positions and shapes of diffraction peak profiles can reveal the imperfect crystalline structure of a sample. The parameters 'size' and 'strain' as obtained from the established Warren-Averbach method need to be used cautiously: in essence the order-independent and order-dependent parts of the line broadening are determined. These require interpretation in terms of structure parameters, for which additional information must often be available. In a case of pure size and strain broadening the order-independent part of the broadening can be interpreted straightforwardly in terms of a size distribution, whereas the order-dependent part cannot readily be related to a specific state of strain. Recent progress in this area is discussed. Non-ideal standard specimens introduce systematic errors. Within the framework of the Warren-Averbach and the single-line Voigt methods, it is shown that this non-ideal situation introduces a constant error and that relative determinations of size and strain are feasible.
A Summary of Low-angle X-ray Atomic Scattering Factors Measured by the Critical Voltage Effect in High Energy Electron Diffraction
Authors: Fox AG , Fisher RM
Published: June 2013

A summary of all the accurate (-0.1%) low-angle X-ray atomic scattering (form) factors for cubic and hexagonal close-packed elements which have been determined by the critical voltage technique in high energy electron diffraction (HEED) is presented. For low atomic number elements (Z ~ 40) the low-angle form factors can be significantly different to best free atom values, and so the best band structure calculated and/or X-ray measured form factors consistent with the critical voltage measurements are also indicated. At intermediate atomic numbers (Z:::: 40-50) only the very low-angle form factors appear to be different to the best free atom values, and even then only by small amounts. For heavy elements (Z ~ 70) the best free atom form factors appear to agree very closely with the critical voltage measured values and so, in this case, critical voltage measurements allow accurate determinations of Debye-Waller factors.
Experimental Determination of Scan-truncation Losses from Low-temperature (16 K) Single-crystal X-ray Measurements
Authors: Destro Riccardo
Published: June 2013

Model intensity profiles have been obtained for biscarbonyl[ 14]annulene by convoluting the Mo Ka spectral distribution with two functions derived from experimental measurements at 16(1) K, up to 26Mo = 110�, of a spherical crystal mounted on a four-circle diffractometer equipped with the Samson low-temperature apparatus. The process includes accurate measurement of the inherent background, treatment of the profiles by numerical Fourier methods, and least-squares fitting. Owing to the instrumental configuration of the diffractometer used in this investigation, the first step of the process has required a careful determination of the X dependence of the background, besides the usual 26 dependence. Truncation losses for the crystal under study, evaluated for several scan ranges, are far larger than usually assumed or predicted.
Excitation of Swift Heavy Ions in Foil Targets. IV. Preequilibrium Energy Losses and Mean Charge States
Authors: Bridwell LB , Hay HJ , Pender LF , Sofield CJ , Treacy PB
Published: June 2013

Studies have been made of the approach to energy-loss and charge-state equilibrium of initially pure charge states of ions, transmitted through thin carbon targets. Ions of Li, F and C1 at 3 MeV per AMU were used. Detailed observations were made of outgoing energy losses and charge-state distributions, for outgoing charges equal to those ingoing. A Monte Carlo analysis is made of the charge changing processes, which allows calculation of energy losses due to projectile charge exchange. The residual electronic target-ionisation loss is analysed to predict in-target charge states of the projectile ions. Using these, a comparison is made between the in-target effective charge for target ionisation, and the averaged ionic charge which fits charge-exchange data.
Electron Impact Ionisation of the Ground State of He+
Authors: Mukherjee KK , Mazumdar PS , Brajamani S
Published: June 2013

Electron impact ionisation of the ground state of He+ is studied by using the distorted wave polarised orbital (DWPO) method in the energy range 61�2-272�0 eV. The present results for the total cross section are in good agreement with the measured values.
Parametrisation of the LCAO Bandstructure of BCC Transition Metals
Authors: Craig BL , Smith PV
Published: June 2013

In this paper we present a direct parameter fitting scheme appropriate to a linear combination of atomic orbitals (LCAO) model� Hamiltonian representation of the BCC transition metals incorporating first and second neighbour interactions. Explicit expressions are given for the one-electron eigenvalues at all of the important symmetry points of the BCC Brillouin zone. This direct parameter fitting scheme is shown to produce an excellent representation of the bandstructure of paramagnetic iron, and yields parameter values little different from those obtained from a full least-squares optimisation of the LCAO model Hamiltonian bandstructure. The extension of this scheme to include more distant interactions, and relativistic and spin-orbit effects, is also discussed.
Painleve Test and Discrete Boltzmann Equations
Authors: Euler N , Steeb W-H
Published: June 2013

The Painleve test for various discrete Boltzmann equations is performed. The connection with integrability is discussed. Furthermore the Lie symmetry vector fields are derived and group-theoretical reduction of the discrete Boltzmann equations to ordinary differentiable equations is performed. Lie Backlund transformations are gained by performing the Painleve analysis for the ordinary differential equations
BD-FRW Cosmology with Bulk Viscosity
Authors: Johri VB , Sudharsan R
Published: June 2013

Exact cosmological solutions of the field equations in Brans-Dicke (BD) theory, with k = 0, FRW metric have been obtained in the presence of bulk viscosity. It is found that constant bulk viscosity leads to an inflationary solution for large values of the BD coupling parameter w. The case of radiative bulk viscosity during the decoupling era is investigated and the production of entropy is estimated.
Coulomb Excitation of 142Ce and 144Nd
Authors: Spear RH , Vermeer WJ , Burnett SM , Cyapong GJ , Lim CS
Published: June 2013

The N = 84 nuclei 142Ce and 144Nd have been Coulomb-excited using 4He, 12C and 160 projectiles. Scattered particles were detected at a mean laboratory angle of 170.6� with an annular silicon surface-barrier detector. The static quadrupole moment f the 2t state was determined for both nuclei. In addition, various electromagnetic transition probabilities involving the 2~, 2~, 1 and 4t states were measured. Taken in conjunction with previous information, the results show that the properties of 142Ce nd 144Nd are well described by the vibrational U(S) limit of IBM-2, and strongly support the proposition that the 2~ level in each nucleus is an essentially pure one d-boson mixed-symmetry state.
Effect of a Rotating Magnetic Field on the Tilting Instability of a Prolate Rotamak
Authors: Bertram WK
Published: June 2013

The effect of a rotating magnetic field on the stability of a rotamak is investigated. Using a simple equilibrium model and the linearised equations of ideal magnetohydrodynamics, it is shown that a rotating field can be a contributing factor in the stabilisation of the tilting instability of a slightly prolate rotamak plasma.
Twinning Accommodation in Highly Aligned Superconducting YBa2Cu307-x
Authors: Zhou JP , Sorrell CC , Dou SX , Bourdillon AJ
Published: June 2013

Defects in the form of twins, slips, kinks and cracks have been studied at room temperature by transmission electron microscopy. In highly aligned YBa2Cu307-x, multiple twinning can be observed, where the orientation of twin planes is varied by accommodation by slipping and kinking. Suitable (TIO) {1l0} slip systems are able to occur in this material. Formation of cracks on subgrain boundaries may occur after twinning in order to relieve transformational and thermal stresses.
Heavy Ion Acceleration by Double-cyclotron Absorption: Some Analytic Approximations
Authors: T Ball Lewis
Published: June 2013

possible to accelerate heavy ions in a magnetised plasma via a process where an ion simultaneously absorbs two gyromagnetic waves whose frequencies sum to the ion gyrofrequency. Analytic approximations to the probability of such double-cyclotron absorption are derived. A particularly simple approximation is presented for the special case where the waves all have frequencies very close to half the ion gyrofrequency. The rate of perpendicular acceleration of the ions due to double-cyclotron absorption is considered, and a simple analytic expression is derived for the case here the waves have the quasimonochromatic distribution mentioned above. One possible application of these proximatio.ns is to investigate the proposal that perpendicular acceleration of oxygen (0+) ions in the Earth's magnetosphere, due to double-cyclotron absorption, may give rise to O+-conic distributions
A Diffusion Reaction Technique for the Preparation of Thick Films of Cuprate Superconductors
Authors: Dou SX , Liu HK , Sorrell CC
Published: June 2013

Liquid- and vapour-phase diffusion have been used to fabricate thick films of V-based, Bi-based, and Tl-based ceramic superconductors. Solid substrates are coated with slurries of complementary compositions and sintered at low temperatures for short times to give dense adherent films that are principally single-phase. This technique can be used to produce reproducible materials of simplified fabrication.
The Global Hubble Constant
Authors: Visvanathan N
Published: June 2013

A review of large-scale investigations of the determination of H is presented. The infrared period-luminosity relation of Cepheids gives distances accurate to -2% to nearby galaxies. Based on the distances of M31, MH, N300 and N2403, a DM of 31 �30 �O� 20 has been derived to the nearby Virgo cluster from the TF relation of spirals at four wavebands. Distances to more distant clusters extending up to a redshift of -10000 km S-I obtained through the CM relation of E galaxies, the TF relation of spirals and the velocity dispersion-luminosity relation of E galaxies give a value of H of 71 km S-I Mpcl when these distances are normalised to a Virgo DM of 31�30. The scatter in the redshift-distance relation of these clusters is -500 km s-I arising from the presence of unaccounted peculiar motions of individual clusters. The magnitude limited all-sky samples of galaxies also give a value of H near 70 km S-I Mpcl once the data are corrected for Malmquist bias. The best value of the global Hubble constant obtained from the redshift-distance data of Virgo and farther clusters, as well as the magnitude limited samples involving various methods of determining distances by different observers, is 73 km S-i Mpcl . Taking into account the error in the calibration of our DM of Virgo we can set a generous error of 10 to this value of H.
Distorted-wave Born Approximation for the Ionisation of Hydrogen by Electrons
Authors: McCarthy IE , Zhang X
Published: June 2013

Matrix elements for ionisation play an important part in electron-atom scattering calculations. Two methods for describing ionisation that can be incorporated into a scattering calculation are tested here against coplanar asymmetric experimental differential cross sections at 150 and 250 eV. They are the distorted-wave Born approximation and the coupled pseudostates method. A method that incorporates the exact boundary condition for three charged bodies describes the data significantly better and shows an important direction for improvement of scattering calculations.
Fabrication of Superconducting YBCO Thin Films on YSZ Substrates
Authors: Bailey A , Alvarez C , Puzzer T , Matthews DN , Sealey K , Russell CJ , Taylor KNR
Published: June 2013

High critical current density thick films of YBCO have been fabricated on yttria stabilised zirconia substrates. The quality and performance of the films was found to depend markedly on the processing of the initial starting powder used to form the printing ink for a fixed film processing cycle. Depending on the powder used, the critical transition temperature, TdR=O), was found to vary between 87 and 91�5 K, and the critical current density was in the range 25 to 1200 A cm-2 at 77 K in zero external magnetic field.
A Review of (e,2e) Studies in Thin Films and Some Recent Results
Authors: Williams JF , Hayes PA
Published: June 2013

The form of the (e, Ze) cross section applicable to high energy symmetric transmission measurements in thin films is given in the plane wave impulse approximation. The difference expected for single crystal, non-single crystal and amorphous films is discussed. For certain kinematics, the measured (e, Ze) coincidence intensity can be related directly to the energy-momentum distribution of the target electron and a map of the occupied electron states can be obtained in principle. Recent experimental work in the authors' laboratory using about 100 A thin films of aluminium/aluminium oxide is discussed. Two peaks in the valence binding energy are seen at 13 and 31 eV whose angular correlations indicate that both are dispersionless and resemble P and S type atomic orbitals of oxygen. Neither peak resembles the free electron structure of aluminium. Improving the electron energy resolution from 4�5 to 1�5 eV while maintaining the momentum resolution constant at about 0�9 A-I did not significantly change the data which indicates the dominant effects of mUltiple scattering.
Photoelectron Spectroscopy of Solids ? VUV Band Structure Studies
Authors: Leckey Robert , Riley John
Published: June 2013

The electronic band structure of solids, including states specific to the surface, may now be explored in very great detail by photoelectron spectroscopy. Variable energy photon sources (synchroton radiation sources) coupled with advanced angle resolving electron spectrometers permit access to emission from specific points within the complete Brillouin zone. The technique of band mapping has now reached a stage where the small k-dependent changes to individual valence bands due to the effects of introduced lattice strain can be observed, for example. The relative importance of emission from surface states, as opposed to bulk band states, can be demonstated dramatically using off-normal emission data. Angle resolved constant initial state spectroscopy has recently been shown to provide details of excited state bandstructure and has clarified the involvement of surface and bulk Umklapp scattering in the photoemission process. The above capabilities of photoelectron spectroscopy are discussed, using metallic and semiconducting examples, and are related to interface problems in general.
Low Energy Electron Scattering From H2
Authors: Brunger MJ , J Buckman Stephen , Newman DS
Published: June 2013

Absolute differential and integrated total cross sections for elastic electron scattering and vibrational excitation of molecular hydrogen have been measured at an incident energy of 1�5 eV. The results are presented and discussed with particular reference to a long-standing impasse which has existed between and within experiment and theory for the near-threshold excitation of the first vibrational state of H2. The integral vibrational cross section is in good agreement (�10%) with previous beam experiments and theory but is some 60% higher than the cross section derived from a swarm analysis.
Particle Acceleration Processes in the Solar Corona
Authors: Melrose DB
Published: June 2013

Theoretical ideas on particle acceleration associated with solar flares are reviewed. A historical outline is used to introduce the various acceleration mechanisms. These are stochastic acceleration in its various forms, diffusive acceleration at shock fronts, shock drift acceleration, resonant acceleration, acceleration during magnetic reconnection and acceleration by parallel electric fields in double layers or electrostatic shocks. Particular emphasis is placed on so-called first phase acceleration of electrons in solar flares, which is conventionally attributed to bulk energisation of electrons (Ramaty et al. 1980). There is no widely accepted theory for bulk energisation, which may be regarded as an enhanced form of heating. Ideas on bulk energisation are discussed critically. It is argued that the dissipation cannot be due to classical resistivity and involves anomalous resistivity or hyperresistivity, e.g., in multiple double layers. The dissipation must occur in very many localised regions. Bulk energisation due to magnetic reconnection is discussed briefly. A model for bulk energisation due to the continual formation and decay of weak double layers is outlined
Resonances in Few-body Systems
Authors: Afnan IR
Published: June 2013

I will show how the resonance poles of the scattering amplitude correspond to eigenstates of the Hamiltonian that is analytically continued into the complex r-space via the dilatation group transformation, and how the corresponding eigenstates satisfy a modified form of the orthogonality condition. As an illustration of the results, I will consider examples of resonances in IT - d, and IX - d scattering as a three-body system.
Inelastic Scattering from 20Ne
Authors: Amos K , Berge L , Steward C , de Swiniarski R
Published: June 2013

Inelastic scattering of 800 MeV protons exciting states of the ground state rotation band of 20Ne is studied using large basis space, microscopic model (Hartree-Fock) wavefunctions and free two-nucleon t-matrices, one of which is based upon the Paris interaction. Results are compared with coupled channels analyses of the data made using Dirac as well as Schrodinger phenomenology. Thereby it is suggested that coupled channels effects in the reaction mechanism are essential in analysis of such higher energy reaction data.
Positron Impact Ionisation of H and He Atoms: The Continuum Model
Authors: Ratnavelu K
Published: June 2013

The continuum optical potential model is used to calculate the ionisation cross sections of H and He by positron impact. The present e+-H result is compared with the recent first measurement of e+ -H ionisation cross sections. The e+ -He calculation is also presented, together with the experimental measurements. A comparison with other theoretical results is also given.
How to Explain the Difference between (?, e) and (e, 2e) Spectroscopic Factors
Authors: Ya Amusia M , Kheifets AS
Published: June 2013

It is shown that the relative line intensity of the main and satellite lines in the atomic shell ionisation spectrum depends significantly on the mechanism responsible for the removal of the electron. This dependence is explained by the influence of many-electron correlations in the initial state of the atom to be ionised, which is considerable when the momentum transferred to the ion is large. This is the case for photoionisation, i.e. the (y, e) reaction under the condition of large photon energy. On the contrary, in electron momentum spectroscopy, such as the symmetric noncoplanar (e, 2e) reaction, the momentum transferred to the ion is typically small and the initial atomic state correlations are negligible. It follows from this that the spectroscopic factors of the different final states of the ion, as defined in the usual way, can be measured only for the (e,2e) reaction, whereas a more involved interpretation is necessary for the (y, e) reaction. Comparison of the calculated spectroscopic factors of Ar II and Xe II 2S ion eigenstates with recent (Y,e) and (e,2e) experimental data has confirmed this conclusion.
Structure of Quantum Fluids at Nonzero Temperature
Authors: Storer RG
Published: June 2013

A method is presented for the calculation of the structure of fluids and gases, such as He, Ne or H2, for which quantum effects are important. The method depends on finding an efficient Monte Carlo sampling technique to evaluate the appropriate averages which lead to the radial distribution function. The method is illustrated by results for the radial distribution function of helium and neon at finite temperatures and densities.
Improved Parton Distributions from the Quark Model
Authors: Bass SD , Schreiber A , Thomas AW , Londergan JT
Published: June 2013

There has recently been significant progress in the calculation of the twist-two piece of the quark/parton distributions corresponding to models like the MIT bag. However, in evaluating the required matrix elements of the quark field operators Signal and Thomas (1988, 1989) resorted to the Peierls-Yoccoz (1957) approximation-albeit with some cautionary remarks. We point out a problem with that approach which is solved by using the Peierls-Thouless (1962) approximation for the hadronic states. The very simple case of a nonrelativistic constant density quark wavefunction is solved in detail.
Excitation of Swift Heavy Ions in Foil Targets. V Production of Rydberg States
Authors: Hay HJ , Treacy PB
Published: June 2013

The results are summarised of previous experiments on the beam-foil excitation of Rydberg states of Br ions containing L vacancies. These show two populations, namely one with high angular momentum .e leading to 'yrast' cascades, and a separate low-.e population. Models for the production of such states in solid targets are discussed, and experiments to test the predictions of these models are described. The target-thickness dependence and downstream decay of the 'yrast' states is consistent with a standard charge-changing and capture model. The low-.e population is very sensitive to the presence of an applied electric field, and it is concluded that such Rydberg states are partly created by the radiative recapture of free 'convoy' electrons which travel physically near their host ions. Detailed level and decay schemes are described for the Br2S+, Ne-like system.
Inhomogeneously Heated Electron Thermal Bottleneck in Semiconductors
Authors: Vaksey AI
Published: June 2013

General phenomenological criteria for the OrIgm of the inhomogeneously heated electron thermal bottleneck in semiconductors are obtained. Different physical situations in solid-state physics are discussed in which the electron bottleneck is described in terms of multi-valued characteristics. A microscopic model of the electron bottleneck in layer semiconductors is suggested and investigated in detail. A novel phenomenon-the cold electon bottleneck in layer semiconductors-is predicted. It is shown that, unlike the hot electron bottleneck, the cold electron one manifests itself in the formation of two (one) S-N shaped or locked looptype sections on the current-voltage characteristics (CVC). Various methods of experimental detection of such bottlenecked eve are discussed.
Enhanced Radio Source Scintillation due to Comet Austin (1989c1)
Authors: Janardhan P , Alurkar SK , Bobra AD , Slee OB
Published: June 2013

Enhanced scintillations in the direction of the quasar 2204+29 (3C441) were observed on 13 May 1990 when the tail of Comet Austin passed in front of it. Comparison with previous observations at 103, 327 and 408 MHz of Comet Halley and at 408 MHz of Comet Wilson show that proper occultation geometry is essential for observing enhanced scintillations. It has been shown that the solar elongation ? during such observations should be large, typically greater than 60� and in no case less than 30� at 103 MHz. At the time of the occultation the scintillation index (r.m.s./mean source flux) was greater than that expected for this source by a factor of 3. The r.m.s. electron density variation /IN, at a distance of 0�9 A.U. from the sun and 7�3� downstream of the nucleus, was found to be 6 cm-3 as compared with 1 cm-3 for the normal solar wind at 1 A.U. The corresponding scale sizes of the turbulence were found to be much finer than normally found in interplanetary scintillation (IPS) caused by the solar wind.
Attachment of Electrons to Molecules at meV Resolution
Authors: Klar D , Ruf M-W , Hotop H
Published: June 2013

A selective discussion of electron attachment to molecules is presented with emphasis on recent studies of SF6, carried out with a novel laser photoelectron attachment (LPA) method in the energy range 0�1-170 me V with an effective energy resolution around 0�1 me V near threshold.
Star Formation at High Redshift
Authors: A Norman Colin
Published: June 2013

The observations relevant to star formation at high redshift are reviewed including radio galaxies, quasars, IRAS objects, and QSO emission and absorption line regions. Low redshift counterparts associated with starburst galaxies are discussed. The relation of galaxy formation, starbursts, and active galaxies and quasars is briefly reviewed. The role of feedback in galaxy formation and massive star formation is briefly analysed.
Optical Studies of Star Formation in Normal Spiral Galaxies: Radial Characteristics
Authors: Ryder Stuart
Published: June 2013

First results of a new, homogeneous CCD imaging survey of nearby southern spiral galaxies in V, I and Ha are presented. Elliptical aperture photometry has been used to determine the deprojected surface brightnesses as a function of galactocentric radius, and thus to trace the past and present star formation behaviour. From a sub-sample of nine mainly barred spirals, we find a couple of notable trends. Firstly, nearly all of the barred spirals show evidence of significant levels of ongoing star formation in the bulge, probably fed by gas inflow along the bar. Secondly, the disk Ha profiles are quite shallow compared with the broadband exponential disks, implying a relative insensitivity of the current star formation rate to the surface density of stars already formed. In both the bulge and the disk, the gas consumption timescales are such as to require gas replenishment, e.g. by radial inflow.
Young Star Clusters in the LMC
Authors: Freeman KC
Published: June 2013

The young globular star clusters in the LMC offer us insights into the formation and early dynamical evolution of globular clusters which are unobtainable from the old globular clusters in our Galaxy. Because these young clusters are so young and populous, they provide an opportunity to measure the upper end of the initial mass function by direct means and also through the dynamical effects of stellar mass loss on the structure of the clusters.
Mechanisms for the Production of Bipolar Flows and Jets in Star Formation Regions
Authors: Bicknell GV
Published: June 2013

Two types of mass ejection are associated with the formation of young stars: poorly collimated bipolar flows and well collimated jets. Some mechanisms which have been suggested for the driving of these flows are reviewed. These include centrifugally driven magnetised winds, magnetic pressure driven winds and bubbles driven by ionised or neutral winds. The idea that the bipolar flows are bubbles driven by a neutral wind seems attractive on both theoretical and observational grounds but the source of the neutral wind-disk or star-is uncertain. It is possible that the jets are driven by magnetic pressure or by a rapidly rotating magnetic field close to the star. However, no definitive theory exists at the present time.
Magnetic Effects in Clouds
Authors: Mestel L
Published: June 2013

A realistic study of the structure and evolution of an interstellar gas cloud must take cognisance of the flux from the galactic magnetic field threading the cloud. If the non-dimensional mass-to-flux ratio is below a critical value, the forces exerted by the locally distorted field can balance gravity in the two trans-field dimensions, while Alfvenic turbulent motions yield support along the field. A super-critical cloud, collapsing with its flux virtually frozen in, may fragment into sub-condensations following spontaneous flattening along the field. Within a sub-critical molecular cloud, the very low degree of ionisation allows the magnetic forces to redistribute flux through the cloud, so that locally denser regions may become super-critical and condense out of the cloud. The Maxwell stresses also transport angular momentum efficiently from a slowly contracting condensation to the surroundings. If flux leakage remains slow throughout all the pre-opaque phases, the magnetic forces and the associated turbulent motions may shift the ultimate mass spectrum towards the high mass end. Most of the remnant flux may be lost by magnetic buoyancy during the pre-main sequence epoch, so possibly supplying a power source for the T Tauri phenomenon.
The Transition from Diffuse to Dense Clouds
Authors: P Snow Theodore
Published: June 2013

Optical and ultraviolet spectroscopy have shown that diffuse interstellar clouds can have a wide range of properties, with especially large variations in the nature of the UV extinction curve and the abundances of molecular species. More subtle variations are found in the properties of the diffuse interstellar bands, and there have been suggestions that elemental depletions from the gas phase into solid dust particles also vary significantly. It is the purpose of this paper to review studies of the relatively diffuse interstellar clouds where these variations occur, and to explore the possible relationship between dust properties, as indicated by UV extinction, and other cloud characteristics. The focus is on relatively dense diffuse clouds, which may be viewed as transitional or intermediate between ordinary diffuse clouds and dark clouds, because in principle the greatest amount of information is available for the intermediate clouds, and because they serve as indicators of processes that may occur in the denser molecular clouds. The paper begins with a brief review of some results from the literature on transitional or intermediate clouds, and then provides a summary of some recent results on one particular cloud, in front of the star BD+31 �643, in the small open cluster IC348, which is part of the Perseus II complex of dark clouds and OB associations. The paper concludes with some tentative speculations about the possible status of the transitional clouds, along with a brief mention of the impact of upcoming instrumental developments on research in this area.
The Physics of Tachyons II. Tachyon Dynamics
Authors: L Dawe Ross , C Hines Kenneth
Published: June 2013

This paper extends the development of a new formulation of the theory of tachyons to encompass tachyon dynamics. Topics discussed include tachyonic energy and momentum, proper mass, force and acceleration.
The 12C(p, g)13N Cross Section near the Ep = 0·46 MeV Peak
Authors: Hinds S , Barker FC
Published: June 2013

The I2C(p,'Y?3N cross section in the neighbourhood of the Ep = 0�46 MeV peak has been measured using thin and thick targets, and fitted using R-matrix formulae. The best value for the radiation width of the first excited state of I3N is 0�53�0�05 eV. eanalysis of earlier thick-target data gives values consistent with this result.
Determination of Barrier Height and Doping Density of a Schottky Diode from Infrared Photoresponse Measurements
Authors: WL Chin Vincent , M Newbury Stephen
Published: June 2013

The impurity doping concentration of a semiconductor is commonly determined by measuring the C-V profile of a Schottky diode. In this work, an alternative method is utilised to determine the impurity doping density of a moderately acceptor-doped Schottky diode using infrared photoelectric measurements. Due to the image lowering effect, the barrier is lowered with the increasing field or reverse bias. Having determined the relationship between the reverse bias and the lowered barrier, the doping density and the zero bias barrier eight from the infrared photo response measurements can be accurately determined.
Analyses of Recent Experimental and Theoretical Determinations of e - H2 Vibrational Excitation Cross Sections: Assessing a Long-Standing Controversy
Authors: W Crompton Robert , A Morrison Michael
Published: June 2013

During the last four years, we have undertaken a major effort to resolve a serious, long-standing discrepancy between various experimental and theoretical determinations of the cross section for the v0 = 0 → v = 1 vibrational excitation of H2. This effort has involved crossed electron-beam molecular-beam measurements of relative angular distributions, measurements of transport coefficients in mixtures of H2 and various rare gases, and ab initio theoretical calculations using a vibrational close-coupling formalism with an exact treatment of non-local exchange effects. The discrepancy remains unresolved—a fact with potentially wide-ranging consequences for beam experiments, theory, and the unfolding of inelastic electron–molecule cross sections from swarm data. New analyses of the transport data and the application of a new method of extrapolating angular distributions beyond the range of measurement sheds light on this disagreement and its implications.
Momentum Transfer Cross Section for e??Kr Scattering
Authors: Brennan MJ , Ness KF
Published: June 2013

The momentum transfer cross section for electrons in krypton has been derived over the energy range Q-4 eV from an analysis of drift velocity and DT/I-' data for hydrogen-krypton mixtures. At energies in the vicinity of the Ramsauer-Townsend minimum, the present work differs significantly from derivations based on analyses of drift velocity data alone. The overall uncertainty in the derived cross section reflects the experimental errors in the transport coefficients, the uncertainty in the cross sections used to represent the hydrogen component in the mixtures, and the uncertainty associated with the X2 minimisation. The present cross section is compared with recent theoretical calculations and other experimental derivations.
Quantum Dots in Strong Magnetic Fields: Stability Criteria for the Maximum Density Droplet
Authors: MacDonald AH , Eric Yang SR , Johnson MD
Published: June 2013

In this article we discuss the ground state of a parabolically confined quantum dot in the limit of very strong magnetic fields where the electron system is completely spin-polarised and all electrons are in the lowest Landau level. Without electron-electron interactions the ground state is a single Slater determinant corresponding to a droplet centred on the minimum of the confinement potential and occupying the minimum area allowed by the Pauli exclusion principle. Electron-electron interactions favour droplets of larger area. We derive exact criteria for the stability of the maximum density droplet against edge excitations and against the introduction of holes in the interior of the droplet. The possibility of obtaining exact results in the strong magnetic field case is related to important simplifications associated with broken time-reversal symmetry in a strong magnetic field.
Spontaneously Symmetry-broken Current-carrying States in Nanostructures
Authors: Rasolt Mark , Perrot F
Published: June 2013

We show that in nanostructure geometry, by approaching the limiting behaviour of a two-dimensional system with large inhomogeneity in the electron density, a spontaneous current-carrying state can develop. We calculate the current patterns of this state and demonstrate that it cannot correspond to the chiral state required to support anyon superconductivity.
An Analysis of Cosmic Ray Air Showers for the Determination of Shower Age
Authors: Sanyal S , Ghosh B , Sarkar SK , Bhadra A , Mukherjee A , Chaudhuri N
Published: June 2013

A sample of 8651 air showers in the size range 104 . 3_106 . 2 has been analysed to determine the distribution of the measured age in terms of (i) the number of showers in a specified size range, and (ii) the radial distances in individual showers. It is shown that the radial age distribution in an individual shower leads to an average shower age approximately the same as the prediction of the electron-photon cascade theory. The other results include a study of the variation of (i) shower age, as measured by the x2-minimisation technique, with shower size of vertically incident showers, and (ii) the measured electron density at any point with its radial distance from the shower axis, as a function of the age of a large shower group with very small spread in size. A comparison of similar measurements with relevant theory is also included.
Close Coupling Theory of Positron?Hydrogen Scattering
Authors: Mitroy J
Published: June 2013

The equations for positron-hydrogen scattering are written as a set of coupled momentum-space Lippmann-Schwinger equations. An explicit expression for the positronium formation matrix element that is suitable for large-scale computation is derived. Elastic and positronium formation cross sections are obtained in the coupled static model as a validation of the method. Calculations at energies below the hydrogen n = 2 threshold are used to study the convergence of observable quantities with increasing numbers of physical Hand Ps states. At higher energies, a series of calculations including multiple hydrogen and positronium states are performed over the energy range from 1�0 to 4�0 Ryd. Cross sections for elastic scattering, excitation of the 2s and 2p hydrogen levels and positronium formation in the Is, 2s and 2p levels are reported.
Ion?Molecule Reactions and Mobilities of SF3+ and SF5+ Ions in SF6 Gas
Authors: Talib ZA , Saporoschenko M
Published: June 2013

Positive ion-molecule reactions in 8F6 were studied in a static drift-tube mass spectrometer using electron impact at 100 eY as the ion source. The ratio of electric field strength to gas number density, E / N, was typically varied from 40-282 Td and pressure ranged from 0�1 to o� 8 Torr. The most important processes were found to be 8Ft + SF6 ---+ 8Ft + 8F6 + F2 and 8Ft + 8F6 ---+ (82Fg)+* ---+ 82Ft + F 2. The interaction potentials for the 8Ft and 8Ft ions in SF6 were also found by using the measured mobility data which were obtained using a pulsed-ion transit-time method. We found that the (12,4, a* = 0�1) core model was adequate to describe the mobility over the range of E / N studied. The zero-field reduced mobilities for 8Ft and 8Ft were determined to be 0�68 and 0�55cm2y-1 s- 1 respectively.
Influence of Metal?Glass Contact on the Dynamic Response of 0.40Ag2O:0.60P2O5 Glass
Authors: Haque NU , Hashmi RA , Anis MK
Published: June 2013

The results of impedance measurements on a low-conducting 0�40Ag20: 060P20S glass are reported in the frequency range 10-3 to 105 Hz and the temperature range 250 to 400 K. The observed dispersions in the complex impedance data are attributed to a barrier effect in the region of the electrodes and are shown to follow simple power law behaviour for low and high frequencies with respect to the loss peak frequency. Using the complex impedance and complex capacitance data, the contact resistance and the corresponding contact capacitance have been worked out. The temperature dependences of the contact resistance R. and the contact capacitance C. are also reported. The activation energy for this glass is found to be 0�50�O�02 eV.
Introduction
Authors: Goddard Dorothy , Haynes Raymond
Published: June 2013

To honour the work and the memory of John Gatenby Bolton, a one-day symposium was held at the Parkes Observatory, Parkes, New South Wales, on 10 December 1993. This special issue of the Australian Journal of Physics contains most of the papers given at the symposium, and presents work, ideas and memories which, directly or indirectly, relate to John Bolton's scientific work over more than thirty years.
John Bolton, Discrete Sources, and the New Zealand Field-trip of 1948
Authors: Orchiston Wayne
Published: June 2013

The field-trip to New. Zealand by John Bolton and Gordon Stanley in 1948 was a crucial step in discovering the nature of discrete radio sources. This paper describes the circumstances surrounding the field-trip and also looks at other investigations in radio astronomy in New Zealand at that time.
Populations of Extragalactic Radio Sources
Authors: Wall JV
Published: June 2013

In the late 1950s and early 1960s, radio sky surveys were the centre of an intense and public debate-Big-Bang versus Steady-State cosmology-the arguments revolving about source counts and statistical interpretations in the face of instrumental complications. The 1965 discovery of the microwave background took the fire from the debate, but left the momentum in place for large-area radio surveys at different frequencies, and for extensive identification/redshift-measurement programs. By the 1970s the data enabled us to start disentangling the different populations of extragalactic radio sources. We could refine our taxonomy, and we could view the possibility of delineating individual cosmic histories and evolutions. We could at least describe a goal to elucidate the birth-life-death cycles of the objects involved [quasi-stellar objects (QSOs) and radio galaxies: together the 'active galactic nuclei' (AGNs)] whose unaccountably prodigious energies somehow produce the beautifully aligned radio structures with which we are now familiar. One part of John Bolton's vision to see how distorted a view of the AGN universe the original long-wavelength surveys provided. One legacy is thus the 'short-wavelength survey' for extragalactic radio sources, which has done so much to balance our picture of the radio sky. And indeed the legacy continues in the form of the immense sky surveys at present under way, complete with their sub-industries of radio-positioning and identification. From these, yet further results are emerging on spatial distribution and the skeleton structure of the universe. It is the purpose of this paper to outline something of this current view of the populations, their differences, similarities and unifying concepts.
Laser Manipulation of Atoms and Atom Optics
Authors: Wang Yu-Zhu , Liu Liang
Published: June 2013

In this paper experiments on laser cooling, collimation and manipulation of a sodium atomic beam, such as the transverse collimation and decollimation of an atomic beam by a standing wave or a misaligned standing wave, longitudinal cooling of an atomic beam by a diffuse light field, sub-Doppler cooling in a blue detuned standing wave, are reported. The basic concept on atom optics is developed. An experiment on a method for the injection of atoms into an atomic cavity is also discussed.
The Steady State Townsend Experiment: Comparison of Boltzmann Equation and Diffusion Equation Analysis
Authors: Robson RE
Published: June 2013

A general solution of the diffusion equation corresponding to an idealised swarm experiment in infinite plane-parallel electrode geometry is given and the result is then specialised to the steady state Townsend experiment. The role of the 'dispersion relation' generated by the diffusion equation is discussed, and the physical meaning of its two zeros explored. It is found that the smaller zero generally allows adequate representation of the electron density distribution downstream of the source, but the larger zero must be found from the full Boltzmann eigenvalue equation in order that the upstream region be represented even qualitatively correctly. The results of a numerical calculation for electrons in water vapour are presented. The procedure adopted by Tagashira et al (1994) to obviate this difficulty is discussed.