bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave synthesis of copper indium gallium (di)selenide nanopowders for thin film solar applications
Authors: Seelaboyina Raghunandan , Kumar Manoj , Venkata Madiraju Alekhya , Taneja Kshitij , Kumar Keshri Anup , Mahajan Sarang , Singh Kulvir
Published: June 2013

This work reports on the synthesis of nanopowder and nanoink of Copper-Indium-Gallium-(di)Selenide (CIGS) (CuIn0.7Ga0.3Se2) of 20–80 nm with a band gap of 1.1 eV by a facile microwave technique. For CIGS synthesis, precursor mixtures consisting of metal acetylacetonates and selenium powder in oleylamine were heated in a microwave at 180–210 °C for 20–60 min. The resultant nanopowder was characterized and optimized for particle size by dynamic light scattering, phase by X-ray diffraction, morphology, and elemental distribution by scanning electron microscopy and band-gap by UV-Vis-near-infrared spectroscopy. CIGS ink, suitable for spin coating and ink-jet printing, was prepared and thin film was deposited and characterized.
Mesoporous coupled ZnO/TiO2 photocatalyst nanocomposites for hydrogen generation
Authors: Hussein Abdulmenan M. , Mahoney Luther , Peng Rui , Kibombo Harrison , Wu Chia-Ming , Koodali Ranjit T. , Shende Rajesh
Published: June 2013

The present work investigates mesoporous coupled ZnO-TiO2 based nanocomposites towards photocatalytic hydrogen generation. The effect of Zn2+ loadings was examined on the photocatalytic activities of the sol-gel derived ZnO-TiO2 nanocomposites employing a structure-directing template. ZnO-TiO2 nanocomposites were characterized by powder X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, nitrogen isotherm, Raman, and electrochemical impedance spectroscopy (EIS) methods. The photocatalytic H2 evolution of the ZnO-TiO2 suspensions was evaluated in an aqueous methanol medium under UV illumination. The Zn2+ concentrations utilized to prepare ZnO-TiO2 nanocomposites were found to have significant effect on the specific surface area, pore volume, and photocatalytic activity. The H2 evolution results obtained with ZnO-TiO2 nanocomposites were compared with H2 generation using commercial TiO2 P25 and individual ZnO nanoparticles. The photocatalytic activity of ZnO-TiO2 composite enhanced significantly as compared to P25 or ZnO nanoparticles. With respect to an increment in Zn2+ loading, the photocatalytic activity of the composite increased and reaching an optimal H2 production of 17.3 ml/g of catalyst for the ZnO-TiO2 composite containing 30 wt. % ZnO (30ZnO). The specific surface area of the samples increased from 19 (single ZnO) to 122 m2/g for ZnO-TiO2 composite containing 50 wt. % ZnO (50ZnO). With an appropriate Zn2+ presence in ZnO-TiO2 nanocomposites, the specific surface area, total pore volume, charge transfer, and photocatalytic activity were significantly improved. Particularly, the samples containing 30 and 50 wt. % (30ZnO and 50ZnO) showed higher photocatalytic activity towards hydrogen generation, which attributed to higher specific surface areas, larger pore volumes, and lower interface resistance as confirmed by adsorption-desorption isotherms and EIS measurements, respectively. Hence, ZnO-TiO2 composites with higher than 50 wt. % ZnO were found to be not favorable to attain reasonable photocatalytic activity toward hydrogen generation as specific surface area and pore volume were drastically decreased.
Large remnant polarization and magnetic field induced destruction of cycloidal spin structure in Bi1−xLaxFeO3 (0 ≤ x ≤ 0.2)
Authors: Yin L. H. , Yang J. , Zhao B. C. , Liu Y. , Tan S. G. , Tang X. W. , Dai J. M. , Song W. H. , Sun Y. P.
Published: June 2013

We prepared a series of Bi1−xLaxFeO3 (0 ≤ x ≤ 0.2) ceramics with a sol-gel method and find that both the magnetization and dielectric constant show an abrupt anomaly near a critical field Hc, which is attributed to the destruction of the cycloidal antiferromagnetic spin structure. The critical field Hc decreases substantially from ∼20 T for the x = 0 sample [Y. F. Popov et al., JETP Lett. 57, 69 (1993)] to ∼2.8 T for the x = 0.17 sample and finally to 0 T for the x = 0.2 sample at room temperature (RT). It is also found that Hc increases with decreasing temperature. The variation of Hc with La substitution and temperature can be ascribed to the change in the magnetic anisotropy and isotropic superexchange interaction, respectively. We have also discussed the magnetodielectric effects in these samples in terms of the Ginzburg-Landau theory and the spin-phonon model. Moreover, increasing the doping level of La to 0.15 greatly improves the RT leakage-current and ferroelectric (FE) properties. A RT square-shaped FE hysteresis loop with remnant polarization (2Pr) as high as ∼64 μC/cm2 is obtained for the x = 0.15 sample. These results may be important for potential applications in BiFeO3-based magnetoelectric devices.
Vortex migration caused by travelling magnetic wave in a 2 in. diameter YBa2Cu3O7−δ thin film
Authors: Wang W. , Coombs T. A.
Published: June 2013

We provide experimental evidence for a vortex migration phenomenon in YBa2Cu3O7−δ (YBCO) thin film caused by travelling magnetic wave. The experiment is carried out on a 2 in. diameter YBCO thin film with a circular-type magnetic flux pump. We found that the travelling wave helps the vortices migrate into the centre of the sample: after the zero-field cooling process, the increase of the flux density in the centre is four times larger than the amplitude of the travelling wave. The reason for this massive vortex migration is probably due to the magnetic stress variation caused by the travelling wave: the magnetic stress increases locally in the crest region while decreases locally in the trough region, which could help the vortices to move locally. A comparison shows that the magnetization by standing wave can be easily predicted by Bean's model while travelling wave causes vortex migration generally much larger than the prediction of Bean's model. It is possible that travelling magnetic wave can be an effective way to magnetize a type II superconductor in considering this unusual vortex dynamics.
The effect of surface roughness on the determination of optical constants of CuInSe2 and CuGaSe2 thin films
Authors: Yin G. , Merschjann C. , Schmid M.
Published: June 2013

To investigate the effect of surface roughness on the calculation of optical constants, e.g., the complex refractive index n+ik or (n,k) of CuIn1−xGaxSe2 (CIGSe) thin films, we took CuInSe2 (CISe) and CuGaSe2 (CGSe) as examples and applied the “Modified Transfer-Matrix (MTM)” method to calculate optical constants with considering the effect of scattering due to surface roughness. Compared to the Transfer-Matrix (TM) method without considering surface roughness, it was revealed that the MTM method could improve the accuracy of calculation. The calculated refractive index values from the MTM method increase by 6.89% for CISe and 2.59% for CGSe in contrast to those from the TM method. In addition, bromine solution was confirmed via Scanning Electron Microscopy and Atomic Force Microscopy to be able to reduce the surface roughness. Calculated results from smoothened samples showed that the accuracy of calculated optical constants was further improved. Finally, optical constants calculated by the MTM method were compared to those from smoothened samples, validating that the MTM method could eliminate the influence of surface roughness on the calculation of optical constants more effectively for CGSe with low surface roughness than for CISe with high surface roughness.
The underestimated thermal conductivity of graphene in thermal-bridge measurement: A computational study
Authors: Yu Chenxi , Zhang Gang
Published: June 2013

The effect of substrate coupling on thermal conductivity of graphene is studied by using molecular dynamic simulations. It was found that heat flux along real suspended single-layer graphene is only 40% with respect to that in the ideal suspended single-layer graphene, due to remarkable temperature jump and thermal contact resistance at the contact region. With the strength of inter-layer (or graphene-substrate) interaction increases, the temperature jump increases and leads to further reduction in heat flux and the estimated thermal conductivity. Our results give a reasonable explanation to the underestimated thermal conductivity of graphene in thermal-bridge measurement.
Bandgap tuning in highly c-axis oriented Zn1−xMgxO thin films
Authors: Kumar Parmod , Malik Hitendra K. , Ghosh Anima , Thangavel R. , Asokan K.
Published: June 2013

We propose Mg doping in zinc oxide (ZnO) films for realizing wider optical bandgap in highly c-axis oriented Zn1−xMgxO (0 ≤ x ≤ 0.3) thin films. A remarkable enhancement of 25% in the bandgap by 30% Mg doping was achieved. The bandgap was tuned between 3.25 eV (ZnO) and 4.06 eV (Zn0.7Mg0.3O), which was further confirmed by density functional theory based wien2k simulation employing a combined generalized gradient approximation with scissor corrections. The change of stress and crystallite size in these films were found to be the causes for the observed blueshift in the bandgap.
Putting Carbon Markets into Practice: A Case Study of Financial Accounting in Europe
Authors: Lovell Heather , Bebbington Jan , Larrinaga Carlos , de Aguiar Thereza Raquel Sales
Published: June 2013

In this paper we explore how carbon markets have entered the world of financial accounting. The advent of the European Union Emissions Trading System (EU ETS) in 2005 provided the opportunity for global climate change concerns to be translated from policy into something that could, and should, be recognised within financial accounting. That is, the EU ETS provided a mechanism whereby greenhouse gas emission allowances acquired a financial value, simultaneously creating an obligation (or liability) on certain European organisations when they emit greenhouse gases. Prima facie, this process created the need for financial accounts of companies covered by the EU ETS to reflect the new commodity of carbon. Disagreement amongst accountants about how to treat emission allowances has arisen, with the initial international accounting guidance issued in late 2004 subsequently being withdrawn, and not yet replaced. Taking this absence of guidance as a starting point, we undertake an empirical project (through a survey, consultation analysis, and interviews) to establish what financial reporting practices are being adopted by participants in the EU ETS, and the level of momentum for standardisation. We draw on sociological theories about accounting, measurement, and markets.
Control of Chaos in the Rössler System
Authors: Corney Stuart
Published: June 2013

The control method of Ott, Grebogi and Yorke (1990) as applied to the
Rössler system, a set of three-dimensional non-linear differential
equations, is examined. Using numerical time series data for a single
dynamical variable the method was successfully employed to control several of
the unstable periodic orbits in a three-dimensional embedding of the data. The
method also failed for a number of unstable periodic orbits due to
difficulties in linearising about the orbit or the tangential coincidence of
the stable manifold and the motion of the orbit with external parameter.
Faddeev Approach to the Nucleon in the NJL model
Authors: Ishii N. , Asami H. , Bentz W. , Yazaki K.
Published: June 2013

The nucleon and the delta are described as solutions of the relativistic
Faddeev equation in the NJL model. We discuss the dependence of the baryon
masses on the particular form of the four-Fermi interaction Lagrangians. Using
the quark–diquark wave function, we calculate some bound state matrix
elements such as the axial coupling constants, magnetic moments of the
nucleon, the pion-nucleon sigma term and the proton-neutron mass difference.
We also try to compare two pictures of describing the baryons in the NJL
model, i.e. the mean-field approximation and the relativistic Faddeev
approach. As a first step, we discuss how to improve the mean-field
approximation by introducing an effective interaction. We also discuss the
perturbative estimate of the deformation of the `vacuum" in the
Faddeev approach.
Spectroscopy of Heavy Mesons Expanded in 1/mQ
Authors: Matsuki Takayuki , Mori Toshiyuki
Published: June 2013

Operating just once with the naive Foldy–Wouthuysen–Tani
transformation on the Schrödinger equation for
Qq bound states, described by the
Hamiltonian which includes Coulomb-like as well as confining scalar
potentials, we have calculated the heavy meson spectrum of
D, D*, B
and B*. Based on a formulation recently proposed,
their masses and wave functions are expanded in
1=mQ, with a heavy quark
mass mQ, up to the second order. The lowest order
equation is examined carefully to obtain a complete set of eigenfunctions for
the Schrödinger equation.
A Study of the pB → Y K Reactions for Kaon Production in Heavy Ion Collisions
Authors: Tsushima K. , Huang S. W. , Faessler Amand
Published: June 2013

Parametrizations of total cross sections sucient for all channels of the
πB → Y K reactions are
completed using a resonance model. As well as discussing the
πN → ΛK reactions,
which were not presented in our previous publications, we present the
differential cross section for πN →
ΛK. This report also aims at presenting
supplementary discussions to our previous work.
Deconvolution of Overlapping Features in Electron Energy-loss Spectra: Determination of Absolute Differential Cross Sections for Electron-impact Excitation of Electronic States of Molecules
Authors: Campbell L. , Teubner P. J. O. , Brunger M. J. , Mojarrabi B. , Cartwright D. C.
Published: June 2013

A set of three computer programs is reported which allow for the deconvolution
of overlapping molecular electronic state structure in electron energy-loss
spectra, even in highly perturbed systems. This procedure enables extraction
of absolute differential cross sections for electron-impact excitation of
electronic states of diatomic molecules from electron energy-loss spectra. The
first code in the sequence uses the Rydberg–Klein–Rees procedure
to generate potential energy curves from spectroscopic constants, and the
second calculates Franck–Condon factors by numerical solution of the
Schrödinger equation, given the potential energy curves. The third, given
these Franck–Condon factors, the previously calculated relevant energies
for the vibrational levels of the respective electronic states (relative to
the v″ = 0 level of the ground electronic
state) and the experimental energy-loss spectra, extracts the differential
cross sections for each state. Each program can be run independently, or the
three can run in sequence to determine these cross sections from the
spectroscopic constants and the experimental energy-loss spectra. The
application of these programs to the specific case of electron scattering from
nitric oxide (NO) is demonstrated.
Effects of Positron Density and Temperature on Large Amplitude Ion-acoustic Waves in an Electron - Positron - Ion Plasma
Authors: Nejoh Y. N.
Published: June 2013

The nonlinear wave structures of large amplitude ion-acoustic waves are
studied in a plasma with positrons. We have presented the region of existence
of the ion-acoustic waves by analysing the structure of the pseudopotential.
The region of existence sensitively depends on the positron to electron
density ratio, the ion to electron mass ratio and the positron to electron
temperature ratio. It is shown that the maximum Mach number increases as the
positron temperature increases and the region of existence of the ion-acoustic
waves spreads as the positron temperature increases. The present theory is
applicable to analyse large amplitude ion-acoustic waves associated with
positrons which may occur in space plasmas.
Electron Attachment and Recombination in Dense Molecular Media
Authors: Hatano Yoshihiko
Published: June 2013

A survey is given of experimental studies of electron attachment and
recombination in dense molecular media, from which information on the effect
of van der Waals potentials or on the existence of surrounding molecules on
these processes is obtained.
Modeling of a Micro-streamer Initiation and Development of ArF Excimer Laser Discharges
Authors: Akashi H. , Sakai Y. , Tagashira H.
Published: June 2013

The dynamics of a constricted filamentary or ‘micro-streamer’
discharge in a discharge-excited ArF excimer laser has been examined using a
two-dimensional fluid model. The entire process on a micro-streamer, from its
initiation and development to extinction, is shown. In the present model, a
micro-streamer is triggered at protrusions which always exist on cathode
surfaces, and develops in the direction of the anode assisted by the high
field induced by space charge. A rise in the gas temperature in the
micro-streamer in the vicinity of a cathode is seen, and which is found to
play an important role in its development. The effect of preionisation
electron density
ne0 on the
streamer development is also examined, and the streamer is found to extend
significantly when
ne0 becomes
low. The results are explained in connection with experimental observations.
Relativistic Effects in Low-energy Electron - Argon Scattering
Authors: McEachran R. P. , Stauffer A. D.
Published: June 2013

We have performed a relativistic treatment at low energy of
electron–argon scattering which includes both polarisation and dynamic
distortion effects. Our results are in excellent agreement with the
experimentally derived momentum transfer cross section and scattering length,
as well as with very recent measurements of the elastic differential cross
section.
Driven Granular Media and Dissipative Gases: Phase Transitions and Instabilities
Authors: Williams D. R. M.
Published: June 2013

We study a simple model of a granular material or powder where the particles
are excited by an external noise source and dissipate energy by inelastic
collisions. Due to the inelastic collisions between particles there is an
effective interaction between them. In one dimension this leads to long-range
correlations between the particles in a gas phase despite the absence of
long-range forces between the particles. In two dimensions the dissipative
effects cause a very sharp liquid–gas phase transition at which the
susceptibility has a pronounced peak. In the presence of a double-welled
potential the inelasticity causes a symmetry-breaking instability where all
the particles cluster into one of the wells.
Wave Equations of Cooper Pairs as Quasiparticles in Superconducting Fermion Systems
Authors: Hieu Nguyen Van
Published: June 2013

The superconducting pairing of fermions is studied in the framework of the
functional intergral approach. The bi-local composite scalar and vector fields
are introduced to describe the singlet and triplet pairings. The static
(time-independent) fields are the superconducting order parameters. From the
variational principle for the effective action of the composite fields we
derive the generalised Ginzburg–Landau equations. They are also the
extensions of the BCS gap equations.
Aspects of Optical Properties in Conventional and Oxide Superconductors
Authors: Marsiglio F. , Carbotte J. P.
Published: June 2013

We review the effect of elastic and inelastic scattering on the normal state
infrared conductivity, and describe modifications to the real and imaginary
parts which result from a transition to an s-wave superconducting state. The
zero frequency limit of the imaginary part is related to the
temperature-dependent penetration depth and, at finite frequency, provides
information about the superconducting gap. In the high
Tc cuprates the gap appears to
have d-wave symmetry. This profoundly modifies both the real and the imaginary
parts of the optical conductivity. After describing these modifications we
introduce the conductivity-derived scattering rate, which directly probes the
inelastic scattering processes, and is much larger in the oxides than in
conventional superconductors. This quantity is also significantly modified by
the d-wave symmetry of the gap.
Redshift and Luminosity Dependence of Linear Sizes of Compact Steep Spectrum Sources and the Quasar/Galaxy Unification Scheme
Authors: Ubachukwu A. A. , Ogwo J. N.
Published: June 2013

We present and analyse plots of linear size–luminosity and linear
size–redshift data for a sample of compact steep-spectrum sources (CSSs)
and use them to investigate the currently popular but controversial
orientation-based unification hypothesis for high-luminosity radio sources.
This is based on the assumption that CSSs belong to a separate class of
object. Our results show that the observed distributions of linear size
(D) as a function of redshift (z)
and radio luminosity (P) are in accord with the unified
scheme in which CSS radio galaxies and CSS quasars are expected to be
indistinguishable in their
D−P/z
correlations. This is particularly true when the two classes of object are
properly matched in redshift. In the unification paradigm, both radio galaxies
and quasars are expected to differ only in their orientation-dependent
properties; all other properties should appear similar.
Nuclear Orientation on Rare Earth Nickel Alloys
Authors: Nishimura K.
Published: June 2013

A hyperfine interaction study of the light rare earth elements, Ce, Pr, Nd and
Pm, in the rare earth nickel and
CeNi2Al5 compounds by means of the
low temperature nuclear orientation is summarised. The magnitudes and
directions of the magnetic hyperfine fields obtained through measurements of
γ-ray anisotropy and angular distributions reveal the magnetic structures
of the ions. The experiments extracted peculiar results for the magnetic
properties of the ions, and show certain novel features of the technique to
the study of solid-state magnetism.
Nuclear Orientation as a Tool for Investigation of Magnetic Multilayers with Rare Earths
Authors: Trhlík Milos , Rotter Milos , Severijns Nathal , Vanneste Ludo
Published: June 2013

Low-temperature nuclear orientation (NO) is presented as a useful tool to
study the behaviour of rare earth (RE) ionic magnetic moments in magnetic
multilayers. NO is shown to give rather direct information about the direction
of RE ionic moments in such low-dimensional systems. In particular, the
perpendicular magnetic anisotropy (PMA) can be directly monitored using RE
atoms as probes. The potential of NO is demonstrated by our recent results,
which concern the Fe/Tb multilayers. We have studied NO of
160Tb in Fe(40 Å)/Tb(x
Å) (x = 5–30) and found that the Tb magnetic moments show
PMA at low external magnetic fields (Bext). PMA of the
Tb spins is found to be more pronounced when the Tb layer is thinner. It was
found that Bext has a complicated influence on the Tb
magnetic moment misalignment, which is connected with an interplay between
PMA, the exchange interactions and the shape and magnetic crystalline
anisotropy.
Dependence of 57Fe Hyperfine Field in Yttrium Iron Garnet on Ionic Radius of Diamagnetic Defects: NMR Study
Authors: Štepánková H. , Kohout J. , Novák P. , Englich J. , Caspary E.-G. , Lütgemeier H.
Published: June 2013

Satellite structure in 57Fe NMR spectra of
In3+ , Sc3+ ,
Ga3+ and Al3+ substituted yttrium
iron garnets (YIG) was analysed taking into account results previously
obtained for ‘antisit’ defects (Y3+ ions on
Fe3+ sites) in nominally pure YIG. The influences of the
diamagnetic substitution on the hyperfine field at the neighbouring iron
nuclei were found to be remarkably dependent on the ionic radius of the
substituent. In the case of two substituents in the vicinity of the resonating
iron, an additivity of their effects within a 15% tolerance interval
was verified.
Magnetic Correlations in Spin Glasses above the Freezing Temperature investigated by High Field Mössbauer Spectroscopy
Authors: Bogner J. , Schachner H. , Reissner M. , Steiner W.
Published: June 2013

The strong dynamics of magnetic correlations are observed by high field
57Fe Mössbauer investigations for the spin glasses
AuFe and Y(Fe, Al)2 in the temperature interval between
the freezing temperature Tf and
approximately 7 to 10Tf. All
recorded spectra can be analysed with a model which takes into account these
dynamics by allowing the formation of correlated states after a stochastically
varying time τoff and their decay after a time
τon, restricting the number of subspectra to the
different number of Fe atoms in the first neighbour shell. Whereas for the
different Fe environments, in addition to centre shift and quadrupole
splitting, different hyperfine fields of the two stochastically formed states
can always be resolved, the same set of τon and
τoff values was obtained for all subspectra above
approximately 4Tf. The external
field hinders the decay of the correlated regions. The temperature dependence
of ¿ on scales with
Tf and exhibits a power law with
exponents of –2 for the Fe-rich and –1 for the Fe-poor compounds.
Neutron Diffraction Study of Tetragonal Zirconias containing Tetravalent Dopants
Authors: Hunter B. A. , Howard C. J. , Kim D.-J.
Published: June 2013

In tetragonal zirconia, the cation is coordinated by two interpenetrating
tetrahedra of oxygen ions, implying two different cation-oxygen bond lengths.
Neutron powder diffraction was used to study tetragonal
ZrO2–2 mol%
Y2O3 incorporating various amounts
of the different tetravalent ions Ge, Ti, Sn and Ce. Precise and accurate
values for the lattice parameters and the variable oxygen position parameter
have been obtained, and from these the bond lengths derived. The results are
compared with those from an earlier X-ray and Raman study on the same
materials. Of interest are the confirmation of the increase in cell volume
occurring when Zr is replaced by the smaller Sn ion, and the observation of
departures from Vegard’s law in the case of substitution of Zr by Ti.
Colossal Magnetoresistance in Ln1-x Ax MnO3 Perovskites
Authors: Goodenough J. B.
Published: June 2013

In the
Ln1-xAxMnO3
pseudoperovskites in which Ln is a lanthanide and A an alkaline-earth atom, an
intrinsic colossal magnetoresistance (CMR) occurs in an O-orthorhombic phase
near an O′-orthorhombic/O-orthorhombic phase boundary. For a fixed
ratio Mn(IV)/Mn = 0·3, the transition through the O phase
from localised-electron behaviour and orbital ordering in the O′ phase
to itinerant-electron behaviour in an R-rhombohedral phase occurs with
increasing geometric tolerance factor t ≡
⟨A-O⟩/√2⟨Mn-O⟩, where ⟨A-O⟩ and
⟨Mn-O⟩ are mean equilibrium bond lengths. The CMR occurs in the
temperature interval Tc ≤ T <
Ts where there is a segregation, via cooperative oxygen
displacements, into a Mn(IV)-rich ferromagnetic phase imbedded in a
paramagnetic phase. The volume of the ferromagnetic, more conductive clusters
increases from below to beyond a percolation threshold in response, above
Tc, to an applied magnetic field and, below
Tc, to a Weiss molecular field. In the O phase, the
magnetic transition at Tc decreases on the exchange of
18O/16O and increases under
hydrostatic pressure. Charge and orbital ordering below a
Tco ≤ Tc is found in
compositions with x ≈ ⅛ or
x ≈ ½. With x ≈
½, the charge-ordered phase CE is tetragonal and antiferromagnetic. An
applied magnetic field stabilises the ferromagnetic, conductive phase relative
to the insulator phase CE to give a second type of intrinsic CMR. For
x ≈ 0·3, there is no static charge and orbital
ordering; but for smaller t, strong electron-lattice
coupling gives a ‘bad metal’ behaviour below
Tc indicative of a dynamic phase segregation as in a
traveling charge-density wave. In
La1-xCaxMnO3
with ½ ≤ x ≤ ⅞, segregation of the
CE x = 0·5 phase and the all-Mn(IV)
x = 1 phase has been reported to take the form of
a static charge-density wave. The origins of this complex behaviour are
discussed.
Magnetoimpurity Theory of Manganites and Other Colossal Magnetoresistance Materials
Authors: Nagaev E. L.
Published: June 2013

A critical review is given of the physics of colossal magnetoresistance (CMR)
materials (manganites and other degenerate ferromagnetic semiconductors). The
basic idea is that their specific properties (the resistivity peak close to
TC, CMR and so on) are not related
to the electron{lattice interaction but are caused by static fluctuations
of the magnetisation induced by ionised donors or acceptors. Their screening
by charge carriers causes fluctuations of their density and, hence,
fluctuations of the intensity of indirect exchange via them. The fluctuations
of the magnetisation induced by the latter are maximally close to
TC, which explains the specific
features of these materials.
Electron Acceleration by a Laser Pulse with a Rising Propagation Speed
Authors: Du Chunguang , Xu Zhizhan
Published: June 2013

The acceleration of an electron by a circularly polarised laser pulse
propagating at a time-rising speed in a plasma is studied. The limitation on
the electron energy gain due to dephasing may disappear. The characteristics
of this non-dephasing direct acceleration scheme are analysed.
Analytic Models of High-ß Reversed Field Pinches
Authors: Sy WN-C
Published: June 2013

A class of simple analytic models for equilibria neighbouring Taylor's force-free states has been examined. It is shown that some members of this class are high-P equilibria which satisfy Suydam's criterion and Robinson's condition for magnetohydrodynamic stability.
A Monte-Carlo Simulation of the Behaviour of Electron Swarms in Hydrogen Using an Anisotropic Scattering Model
Authors: Blevin HA , Fletcher J , Hunter SR
Published: June 2013

Hunter (1977) found that a Monte-Carlo simulation of electron swarms in hydrogen, based on an isotropic scattering model, produced discrepancies between the predicted and measured electron transport parameters. The present paper shows that, with an anisotropic scattering model, good agreement is obtained between the predicted and experimental data. The simulation code is used here to calculate various parameters which are not directly measurable.
Energy Principle for Compressible Dissipative Magnetoplasma
Authors: Hosking RJ
Published: June 2013

Qualitative evaluation of the influence of dissipation on plasma stability foIlows from a generalized energy principle.
Finite Ligand Size and Sternheimer Antiscreening in Lanthanide Ions
Authors: Ahmad S , Newman DJ
Published: June 2013

A finite ligand affects the quadrupole potential at the nucleus of a lanthanide ion in two ways: it produces a positive exchange charge in the region of overlap and it reduces the antiscreening of the point-charge interaction due to charge penetration. We estimate the magnitude of the exchange charge contribution in the system Pr3 + - Cl- using a simple model based on calculating the change in the antiscreening of a point charge as it moves towards the lanthanide ion. A significant contribution is produced, which is not sensitive to the position of the exchange charge, showing that the conventional antiscreening factor )' '" cannot properly represent� the effect of anti screening on the ligand contributions to the nuclear quadrupole potential.
Corrigendum: Thermal Instability of a Partially Ionized Plasma
Authors: Sharma RC , Sharma KC
Published: June 2013

In equation (19), A should be replaced by A' = Ar-iAi where
The Galactic Distribution of Pulsars
Authors: Manchester RN
Published: June 2013

Data from the second Molonglo pulsar survey have been analysed to determine the galactic distribution of pulsars. The results show that the total number of active pulsars in the Galaxy (assuming that only 20% of these are observable because of beaming effects) is about 2x 106 ? For a mean active lifetime of 107 years, this implies that pulsars are born at the rate of one every five years. It is also shown that there is a correlation between pulsar period and distance from the galactic plane, with long period pulsars being, on the average, more distant from the plane than short period pulsars.
Pulsar Microstructure: Periodicities, Polarization and Probes of Pulsar Magnetospheres
Authors: Cordes JM
Published: June 2013

This paper discusses characteristic time scales, periodicities and polarization of microstructure in pulsar signals. The relationship of microstructure polarization to the polarization of subpulses and the average profile is analysed in detail for PSR2016+28. For this pulsar the contributions of micropulses to the variance of the intensity vary with radio frequency v approximately as V-I and the characteristic time scale varies as v-a, with 0�2 ;S IX ;S 0�3. In summarizing possible interpretations of microstructure, we distinguish between angular beaming and temporal modulation processes that can cause intensity variations. We outline, with regard to the frequency dependence of pulse structure, how micropulses can be used to probe the depth and variability of the emission region.
Progress Report on the Binary Pulsar 1913+16
Authors: Fowler LA , Cordes JM , Taylor JH
Published: June 2013

We report on the current status of observations of the binary pulsar PSRI913+16. The average pulse shape, polarization and spectrum have been found to be similar to those of other pulsars. We find no evidence for irregularities in the rotational frequency of the pulsar. With present measurement uncertainties, timing measurements after a few more years will yield estimates of the individual masses of the pulsar and its companion. the orbital inclination and the derivative of the orbital period. Upper limits on the last parameter are already inconsistent with theories that predict dipole gravitational waves; its measurement will test a specific prediction of general relativity theory and will indirectly demonstrate the existence of gravitational waves.
Secular Decreases in the 927 MHz Emission from the Supernova Remnants Cas A and Tau A
Authors: Vinyajkin EN , Razin VA
Published: June 2013

This paper presents 927 MHz flux densities for the SNRs Cassiopeia A and TaurusA relative to those for the radio galaxies Cygnus A and Virgo A and for the Orion Nebula. The measurements were made in October-December 1977 with the 10 m radiotelescope at the Staraya Pustyn' (NIRFI) RadioastronomicaI Observatory. Comparison between these data and the absolute flux density measurements of Razin and Fedorov (1963) yields an annual decrease in flux density of 0�95%�0�04% for CasA and 0�18%�0�01% for TauA (14�2%�0�6% and 2�7%� 0�1% respectively over the past 15 years).
A Comparison of Effective Two-nucleon Interactions Appropriate for Use in Analyses of Inelastic Nucleon Scattering
Authors: Smith R , Amos K
Published: June 2013

A comparison of the spatial and fourier components of a number of effective two-nucleon interactions, suitable for use in analyses of inelastic nucleon scattering data, is complemented by a comparison of their use in a variety of distorted wave analyses. Specifically, a set of effective interactions derived from 'realistic' potentials have been compared, not only with each other, but also with a semiphenomenological valence interaction that has been developed over recent years and has been used extensively in reaction data analyses.
Resonance Neutron Capture in 138Ba and 140Ce and the Prompt Neutron Correction to ?-ray Detectors
Authors: de L Musgrove AR , Alien BJ , Macklin RL
Published: June 2013

The neutron capture cross sections of 138Ba and 140Ce have been measured with high energy resolution between 3 and 100 keY using the capture cross section facility at the 40 m station of the Oak Ridge Electron Linear Accelerator. The average s-wave level spacings are <D)s = 6�3 � 1 �7 and 3�2 � 0�8 keY for 138Ba and 140Ce respectively. The deduced s-wave neutron strength functions are 104So = 1�0�0�4 and 1�54�0�53 respectively, and the average s-wave radiative widths are <r,)s = 55�20 and 35�9meY. The p-wave neutron strength functions are 104S1 ~ 0�03 and 0�32�0�12 respectively. The average 30 keY Maxwellian capture cross sections are 3�9�0�8mb for 138Ba and 7�7 � 0�9 mb for 140Ce. A more rigorous treatment of the prompt neutron correction for l'-ray detectors is described, and it is shown that previously published results for 138Ba have underestimated this correction. The 140Ce data provide excellent corroboration for the calculated magnitude and time dependence of the prompt neutron correction.
Heat Capacities and Grüneisen Parameters for NaF and NaBr below 25 K
Authors: Birch JA , Collins JG , White GK
Published: June 2013

Heat capacities of NaF and NaBr have been measured from 2 K to around 20 K. Limiting values of the Debye temperature e~ of 488�2 K (NaF) and 224�6� 1 K (NaBr) agree with e~1 within experimental errors. Values of the Griineisen parameter y(T) lie between 0�9 and 1�1 in the range below 20K.
Optical Positions for Identifications from the MC2 and MC3 Catalogues
Authors: Murdoch HS , Sanitt N
Published: June 2013

Optical positions measured from the Palomar Sky Survey prints are given for objects identified with MC2 and MC3 radio sources. A comparison with other published optical positions for sources in common suggests an r.m.s. error of o� JH -0. 35H arc in each coordinate. Comparison of previously published optical positions from the Sydney measuring machine with subsequent more accurate radio positions indicates an r.m.s. error of 0�28H arc in each coordinate for the optical positions of stellar objects.
Spectroscopy of Ionic Crystals: The Hydrogenated Calcium Fluoride System
Authors: Jones GD
Published: June 2013

This paper reviews the spectroscopy of ionic crystals, taking the system of hydrogenated calcium fluoride crystals containing trivalent rare earth ions as a specific example to illustrate the kinds of information that can be obtained by spectroscopic means. The discussion is primarily directed to solid state physicists who are not specialists in spectroscopy.
A Model of Solar X-ray Bright Points and Ephemeral Active Regions
Authors: Piddington JH
Published: June 2013

Solar ephemeral active regions may provide a larger amount of emerging magnetic flux than the active regions themselves, and the origin and disposal of this flux pose problems. The related X-ray bright points are a major feature of coronal dynamics, and the two phenomena may entail a revision of our ideas of the activity cycle. A new large-scale subsurface magnetic field system has been suggested, but it is shown that such a system is neither plausible nor necessary. The emerging magnetic bipoles merely represent loops in pre-existing vertical flux tubes which are parts of active regions or the remnants of active regions. These loops result from the kink (or helical) instability in a twisted flux tube. Their observed properties are explained in terms of the flux-rope theory of solar fields. The model is extended to some dynamical effects in emerging loops. Further observations of ephemeral active regions may provide important tests between the traditional and flux-rope theories of solar magnetic fields.
Definition of Heat in Open Systems
Authors: Smith DA
Published: June 2013

Existing definitions of heat in open systems are considered with the aim of providing acceptable physical motivation in restricted circumstances. The extent to which these definitions are independent of the usual concept of heat in closed systems is clarified: they all have the feature that internal energy may be transferred by convection in workless adiabatic processes. The global definitions are compared with various definitions of heat flux in irreversible thermodynamics. As the domain of applicability of these definitions is wider than that of equilibrium thermodynamics, it is suggested that a minimal check for any definition of heat flux be that it agree with the global definition of heat flow between equilibrium states in as wide a range of circumstances as possible.
Pion Charge Exchange Scattering at High Energies
Authors: Saleem M , Rafique M , Bhatti Sanaullah , Aleem Fazal-e
Published: June 2013

By a phenomenological choice of the residue functions, a very good fit with experiment for the pion-nucleon charge exchange reaction at Fermilab energies is obtained on a simple Regge-pole model using a quadratic p trajectory and energy-independent parameters.
An Interpretation of Anomalous Intensity Ratios Within the Hydrogen-like La Doublet in Optically Thick Laser-produced Plasmas
Authors: Irons FE
Published: June 2013

It is shown that the anomalous intensity ratios of the fine-structure components of MgXIIL. And Al XIII L. observed in optically thick laser-produced plasmas can be explained in terms of the usual radiative and collisional processes provided aIIowance is made for the effect of differential motion on the plasma opacity. The Doppler effect associated with differential expansion causes the red component of the doublet in the peripheral plasma region to overlap the blue component in the central region, leading to preferential absorption of the blue component. Model calculations give intensity ratios in good agreement with experiment, and explain such details of the line profile structure as the so-caIIed short-wave satellite and a component spacing in excess of the theoretical optically thin value. This study further demonstrates the major role played by differential motion in shaping the emergent profile of an opticaIIy thick line from a laser-proouced plasma.
Barrier Theory Based on Half-barrier Penetration
Authors: Heading J
Published: June 2013

Special methods are investigated for. the calculation of reflection and transmission coefficients for a real symmetric potential barrier. These methods, involving half-barrier penetration only, are both of physical and mathematical interest, and they also afford a considerable saving in time when numerical procedures are necessary in the case of analytically nonsoluble models.
Shifts of Coherent Light Beams on Reflection at Plane Interfaces between Isotropic Media
Authors: Turner RG
Published: June 2013

Previous experimental and theoretical work on both longitudinal and transverse shifts of light beams at totally reflecting interfaces is briefly reviewed and the discrepancy between the predictions of the two principal theoretical approaches is discussed. A theoretical treatment, valid for an interface between any two media, is presented. The intensity profile of the reflected beam is the same as that of the incident beam (albeit shifted in the reflecting interface) only for certain polarization states of the incident beam and provided that the reflection parameters of the interface meet certain conditions. If these conditions are not met the reflected beam profile suffers distortion and, possibly, deviation from its expected direction. Because the polarization state of a beam is, in general, altered by reflection, measurements of the shifts over a large range of angles of incidence at a single reflection are needed in order to verify the predictions.
The Radio Properties of a Complete Sample of Bright Galaxies
Authors: Harnett JI
Published: June 2013

Results are given for the radio continuum properties of an optically complete sample of 294 bright galaxies, 147 of which have been detected. Data were obtained with the 408 MHz Molonglo Radio Telescope. The radio luminosity functions for all galaxies and for spiral galaxies alone are derived and the radio emission for different galaxy types is investigated. Spectral indices of 73 galaxies which had been detected at other frequencies were derived; the mean index of a reliable subsample is <ex) = -0,71.
Electron-Photon Coincidence Studies in Sodium
Authors: Teubner PJO , Furst JE , Riley JL
Published: June 2013

Three techniques are described from which the scattering parameters A and X can be measured in electron-photon coincidence studies of the 32P state of sodium. The relative sensitivity of the angular correlation and polarized photon techniques is discussed for states which have significant hyperfine structure in the excited state. The phenomenon of zero field quantum beats is described in the framework of the electron impact excitation of sodium. It is shown that the amplitude of the beat pattern depends on the parameter it. The use of the beat pattern to determine A is discussed.
The Shape of the Current?Voltage Curve for a Flame Ionization Detector with Two Ionic Components
Authors: Bolton HC
Published: June 2013

A theory of the shape of the current-voltage curve of the flame ionization detector when one positive ion, usually oxonium hydrate, is dominant has been extended to include a second positive ion, ammonium hydrate. The extension, though only to first order, accounts for the shape of some experimental curves.
Surface Topography Measurement and Analysis
Authors: Thwaite EG
Published: June 2013

Topography is one of the most important of the physical characteristics of surfaces influencing their significant technical properties. The systematic study of the fine structure of surfaces only became possible when instruments with sufficient magnification to resolve the vertical structures became available. A resume is given of current and prospective quantitative techniques for determining surface topographical properties. The topics of modelling and the interpretation of data which are mainly in the form of time series are discussed.
Excitation of Swift Heavy Ions in Foil Targets: Visible Radiation from Fe, Ni and Cu
Authors: Hay HJ , Newton CS , Treacy PB
Published: June 2013

Studies have been made of visible radiation from highly stripped 100-144 MeV Fe, Ni and Cu ions excited by transmission through thin carbon foils. All the observed transitions in the region 180-530 nm were identified with hydrogenic transitions of An = 1 or 2, in charge states between 14 and 22. Light intensities observed are proportional to the outgoing beam charge-state distributions. For thin foils � 20 Ilgcm- 2 ) the light output is less than that from beams in charge equilibrium. It is shown that these observations are consistent with a surface excitation mechanism that depends on the prior formation of multiply excited ions in the solid target.
The Physics of Low-energy Electron-Molecule Collisions: A Guide for the Perplexed and the Uninitiated
Authors: A Morrison Michael
Published: June 2013

The essential physical features of low-energy electron-molecule scattering are described in a qualitative fashion. The context for this discussion is provided by the frame-transformation picture, which entails a 'partitioning' of the quantum scattering problem according to the relative importance of various physical interactions. This picture is then used as the basis for a qualitative overview of several contemporary theoretical techniques for solving the quantum scattering problem that are based on eigenfunction expansions of the system wavefunction and for representing the electronmolecule interaction potential. Finally, progress in three specific problem areas of recent interest is surveyed. The emphasis throughout is on non-resonant elastic scattering and ro-vibrational excitation.
Quantum Electrodynamics in Strong Magnetic Fields. III. Electron?Photon Interactions
Authors: Melrose DB , Parle AJ
Published: June 2013

A version of QED is developed which allows one to treat electron-photon interactions in the magnetized vacuum exactly and which allows one to calculate the responses of a relativistic quantum electron gas and include these responses in QED. Gyromagnetic emission and related crossed processes, and Compton scattering and related processes are discussed in some detail. Existing results are corrected or generalized for nonrelativistic (quantum) gyroemission, one-photon pair creation, Compton scattering by electrons in the ground state and two-photon excitation to the first Landau level from the ground state. We also comment on maser action in one-photon pair annihilation.
A Theoretical Study of an Airborne Laser Technique for determining Sea Water Turbidity
Authors: Phillips DM , Koerber BW
Published: June 2013

An airborne laser technique for remote measurement of sea water turbidity is studied theoretically. The limits of validity of an analytic model are established using Monte Carlo simulation computations. It is shown that, if the field of view of the airborne receiver is large enough, the backscatter signal from the water is attenuated at a rate determined by the absorption coefficient of the water. Apart from geometrical factors, the amplitude of the backscatter signal at the water surface depends on the scattering coefficient of the water. The method therefore allows both the absorption and scattering coefficients of water to be determined independently.