bluuebunny/crossref_metadata_2025 huggingface dataset:
On the windows in the absorption spectrum of an ensemble of oscillators embedding an impurity oscillator
Authors: Breton J. , Hardisson A. , Lefebvre R. , Mauricio F.
Published: December 2004

The windows in the absorption spectrum of a harmonic oscillator coupled to a bath can be given a two‐parameter form identical to the Fano windows in the absorption cross section of an atom with an autoionizing state.
On the structure of the diagonal conditions
Authors: Erdahl R. M.
Published: December 2004

Some structural features of the diagonal problem of reduced density matrix theory are investigated by considering the cone Br introduced elsewhere. In some special cases, we discover a very tight connection between the group structure of Gr, the invariance group of Br, and the convex structure of Br. We also state a general theorem that relates the convex structure of Br to the group structure of Gr.
Comparisons of the RPA, SCRPA, Tamm–Dancoff, and full CI methods by analysis of their transition density matrices, oscillator strengths, and energy moments of oscillator strengths for the electric dipole transitions from the ground state of the B+ ion (frozen K‐shell model)
Authors: Larson Everett G.
Published: December 2004

The RPA, SCRPA, Tamm–Dancoff, and full CI methods are compared by analyzing their transition density matrices, oscillator strengths, and energy moments of oscillator strengths for the 1Sground – 1Podd transitions of the 4‐electron B+ ion in the frozen K‐shell approximation. It is found that the RPA gives transition density matrices that are aligned nearly as well as possible along those of the full CI, but have vector lengths that are significantly too long. The corresponding transition energies are significantly too small. These errors compensate to give oscillator strengths for the dominant transition that, for all forms of the oscillator strength, are within 1.6% of the corresponding full CI values. The SCRPA gives better transition density matrices than the RPA, but poorer oscillator strengths. The Tamm‐Dancoff approximation gives very good values for the mixed length‐velocity form of the oscillator strength. The RPA gives a static electric dipole polarizability that is nearly 20% larger than that of the full CI. The SCRPA gives a value 15% smaller than—and the Tamm‐Dancoff approximation gives a mixed length‐velocity value that is 11% larger than—that of the full CI. Other energy moments of oscillator strengths are also reported. Certain other approximations related to the RPA and the SCRPA are reported as well.
Reduced hamiltonian orbitals. II. Optimal orbital basis sets for the many‐electron problem
Authors: Absar Ilyas
Published: December 2004

Optimal orbital exponents are approximated by minimization of the reduced Hamiltonian orbital ground state energy. They appear to be as good as and are obtained at much less expense than the values derived by the usual SCF exponent optimization scheme. Partitioning of energy into 0‐energy, 1‐energy, and 2‐energy (Absar and Coleman, Int. J. Quant. Chem. 10, 319 (1976); Chem. Phys. Lett. 39, 60 (1976)) is used to study the variation in the electronic energy surface upon variation of orbital exponents. The 1‐energy operator, the natural orbitals of which are the reduced Hamiltonian orbitals, is compared with the SCF operator.
Representable reference density matrices applied to the graphical description of the Coulomb hole in the 1s2(2p)21S state of the B+ ion
Authors: Larson Everett G.
Published: December 2004

Representable reference density matrices are applied to the graphical description of the Coulomb hole in a CI wave function for the first excited 1S state of the four‐electron boron ion B+. It is found that a satisfactory picture of the Coulomb hole emerges only when the symmetry of the correlated wave function is recognized in the construction of the reference full‐density matrix.
Mathematical basis of approximate MO theories: Origin of mulliken's magic formula
Authors: Carbo Ramon , Arnau Caterina
Published: December 2004

The mathematical basis for the Ruedenberg's and Mulliken's approximations is given in a general framework.
Study of the quality of Gaussian basis sets for carbon and silicon: Calculations on methane and silane
Authors: Daudel R. , Poirier R. A. , Goddard J. D. , Csizmadia I. G.
Published: December 2004

A number of Gaussian basis sets for carbon and silicon have been examined in terms of the one‐electron properties of methane and silane. The convergence of the properties to their limiting values is not monotonic but, in general, a representation that involves five Gaussian functions per occupied atomic orbital on the heavy atom is sufficient to closely approach the limits. A relationship between the sizes and partitioned electronic energies is shown to hold to a good approximation for the Boys spatially localized molecular orbitals employed in this study.
Surface structure and energy spectra of localized states
Authors: Stȩślicka Maria , Kempa Krzysztof
Published: December 2004

A simple model for surface reconstruction is developed utilizing the next‐nearest‐neighbor approximation within the framework of molecular‐orbital theory. Exact energy expressions for this model and various special cases are derived, and they are illustrated by numerical results. The influence of a very weak surface deformation on the energy spectrum of surface states is also discussed.
Cyanide–Isocyanide isomerization in the structural isomers of cyanogen isocyanate
Authors: Moffat J. B.
Published: December 2004

The cyanide‐isocyanide isomerization has been studied with ab initio calculations in an STO‐3G basis as applied to NCNCO, NCCNO, NCOCN, and NCONC, and the corresponding isocyanides. Geometry optimization has been performed on these cyanides, their isocyanides, and their hypothetical transition states. The energies of isomerization were calculated to be 42.2, 29.8, 44.6, and 41.4 kcal/mol, respectively, while the energy barriers were found as 84.3, 67.5, 107.9, and 106.8 kcal/mol. Overlap populations and atomic charges were employed to provide simple correlations of the results.
On the use of a MO polarized basis for the analysis of the interaction energy in molecular interactions: Application to amine complexes
Authors: Bonaccorsi R. , Palla P. , Cimiraglia R. , Tomasi J.
Published: December 2004

A variant of the interaction energy decomposition scheme proposed by Morokuma which gives more emphasis to polarized MOS is presented and tested on complexes of amines with Li+, BH3, and SO2. A more systematic utilization of polarized MOS (i.e., of orbitals of the interacting molecules computed with the SCF formalism in the Coulombic field of the other molecular components of the system) is adopted, and the connection of this decomposition of the supermolecule interaction energy with perturbation approaches utilizing such polarized MOS is discussed.
Field theory of chemical reactions. I. Ideal space representation of A + BC → AC + B processes
Authors: Varracchio E. Ficocelli
Published: December 2004

A new quantal approach to the problem of chemical reactions, of the type A + BC → AC + B, is proposed. The general formalism is based on a change of representation for the Hamiltonian system, such that in the new (ideal space) representation the transformed Hamiltonian may present, simultaneously, information on both the “reactants” and the “products” of the dynamical process. The change of representation is carried out by means of a unitary transformation that physically corresponds to creating bound BC and AC molecules, respectively, starting from free atoms. The transformation is explicitly realized by using models available in the literature, and the ideal space Hamiltonian is fully obtained, showing that it contains, in its structure, all the channels (inelastic, reactive, dissociative, etc.) available to the system. A discussion of the dynamics, at the light of the new Hamiltonian, seems to indicate that the theory will be particularly suited for numerical applications to the problem of chemical reactions and, more generally, that it may lead to a “unified” approach for both the subreactive and rearrangement regimes, in atom‐diatom encounters.
Symmetrization of operator matrix elements
Authors: Taylor Peter R.
Published: December 2004

The method of Dupuis and King for generating matrix elements of a totally symmetric one‐electron operator in terms of symmetry‐distinct integrals only is generalized to the case of nontotally symmetric operators. For operators constructed from two‐electron integrals, explicit reduction of integral processing to permutationally inequivalent symmetry‐distinct integrals only is described, while for one‐electron operators further reductions are derived using double coset decompositions. Finally, some computational consequences of this approach are briefly discussed.
Multiple solutions of the valence‐universal coupled‐cluster equations for Be, B+, and C2+
Authors: Jankowski K. , Malinowski P.
Published: December 2004

Sets of nonlinear equations for the cluster amplitudes of the valence‐universal coupled‐cluster (VU–CC) method have been solved to obtain physically meaningful multiple solutions for Be, B+, and C2+. The wave operator is taken in Lindgren's normal ordered exponential form and the completeness of the model space is postulated. The cluster operator is restricted to its one‐ and two‐electron components that are represented in terms of radial amplitudes defined by the configurational excitations (VU–CCSD/R method). Five solutions giving rise to 10 approximate energies of four 1S states are obtained and discussed. These are the first multiple solutions documented for a nonmodel system. Some attention is paid to the problem of the efficiency of various methods in obtaining alternative solutions and to some consequences of the availability of alternative solutions. © 1993 John Wiley & Sons, Inc.
Collision‐Induced intensity of the b1Σg+−a1Δg transition in molecular oxygen: Model calculations for the collision complex O2 + H2
Authors: Minaev Boris F. , Lunell Sten , Kobzev G. I.
Published: December 2004

Ab initio configuration interaction (CI) calculations have been performed for the O2 + H2 complex in a trapezoidlike collision arrangement with C2v symmetry. The potential energy surfaces of the four lowest states of this van der Waals complex (arising from the X3 Σg−, a1 Δg, and b1 Σg+ states of the oxygen moiety), as well as the collision‐induced b1 Σg+ − a1 Δg electric dipole transition moment (Mb–a), have been analyzed for different CI expansions, using as a reference determinant the restricted open‐shell Hartree–Fock (ROHF) function for the ground state of the complex H2(X1 Σg+) + O2(X3 Σg−). The geometry optimized at the ROHF/6–311G** level was refined by a partial optimization at the CI level scanning the intermolecular distance. The equilibrium distances for the X, a, and b states have been found to be a slightly different in the region 3.02–2.98 Å. The larger binding energy of the b1 Σg+ state (2.96 kJ/mol) in comparison with the a1 Δg (2.1 kJ/mol) and ground X3 Σg− states (1.35 kJ/mol) presumably could be explained as resulting from charge‐transfer interactions. A good convergence of the calculated transition moment Mb–a for the larger CI expansions (approximately 50,000 configuration‐state functions) has been obtained. The calculated collision‐induced intensity of the b1 Σg+‐a1 Δg and a1 Δg−X3 Σg− transitions in molecular oxygen are in reasonable agreement with recent experimental data for several foreign gases. © 1994 John Wiley & Sons, Inc.
The effects of static quartic anharmonicity on the quantum dynamics of a linear oscillator with time‐dependent harmonic frequency: Perturbative analysis and numerical calculations
Authors: Sarkar Pranab , Bhattacharyya S. P.
Published: December 2004

The effects of quartic anharmonicity on the quantum dynamics of a linear oscillator with time‐dependent force constant (K) or harmonic frequency (ω) are studied both perturbatively and numerically by the time‐dependent Fourier grid Hamiltonian method. In the absence of anharmonicity, the ground‐state population decreases and the population of an accessible excited state (k = 2, 4, 6…) increases with time. However, when anharmonicity is introduced, both the ground‐ and excited‐state populations show typical oscillations. For weak coupling, the population of an accessible excited state at a certain instant of time (short) turns out to be a parabolic function of the anharmonic coupling constant (λ), when all other parameters of the system are kept fixed. This parabolic nature of the excited‐state population vs. the λ profile is independent of the specific form of the time dependence of the force constant, Kt. However, it depends upon the rate at which Kt relaxes. For small anharmonic coupling strength and short time scales, the numerical results corroborate expectations based on the first‐order time‐dependent perturbative analysis, using a suitably repartitioned Hamiltonian that makes H0 time‐independent. Some of the possible experimental implications of our observations are analyzed, especially in relation to intensity oscillations observed in some charge‐transfer spectra in systems in which the dephasing rates are comparable with the time scale of the electron transfer. © 1995 John Wiley & Sons, Inc.
Localized planar atomic hybrids
Authors: Rees D. , Hall G. G.
Published: December 2004

The derivation of localized atomic hybrids in the plane is discussed using their definition as simultaneous eigenfunctions of the x and y position operators, when these are represented by commuting matrices in a finite basis. The use of alias functions, as introduced in the preceding paper, to produce commuting matrices is described and illustrated. Full results are obtained for any regular polygon. The extension to three dimensions allows the sp2 trigonal, sp2d square, and sp2d2 pentagonal hybrids to be derived. The theory also allows the radial factors to differ so that several shells of hybrids can be found at once. The double trigonal configuration is described as an example. The implications for any calculation of a molecular dipole moment are discussed. © 1995 John Wiley & Sons, Inc.
A semiempirical study of heterocycle oligomers and polymers in different dielectric media
Authors: Jüuurimäaue Tiit , Strandberg Marek , Karelson Mati , Calais Jean‐Louis
Published: December 2004

Four common five‐membered heterocycles—pyrrole, phosphole, thiophene, and furan—and their oligomers with the chain length of 2, 4, 6, and 10 units have been studied quantum chemically using the semiempirical PM3 parameterization. The oligomers of pyrrole and phosphole with the homolytically dissociated NH bond and PH bond, respectively, and oligomers of thiophene and furan with one electron removed per monomer unit (4n + 2 π‐electron bipolaron systems) have also been studied. The electronic properties of the respective polymers were extrapolated from the oligomer data. Bulk polymer effects on the electronic structure were modeled using the self‐consistent reaction field theory in the multicavity approximation (MCa SCRF). © 1995 John Wiley & Sons, Inc.
Electric‐field gradients and magnetic hyperfine parameters of square‐pyramidal [M(CN)5]3− (M = Co, Rh, and Ir) complexes
Authors: Nogueira S. R. , Guenzburger Diana
Published: December 2004

Density functional self‐consistent spin‐polarized calculations with the discrete variational method were performed to obtain the electronic structure of the paramagnetic complexes [Co(CN)5]3−, [Rh(CN)5]3−, and [Ir(CN)5]3− of square‐pyramidal geometry. All electrons were kept in the variational space. Electric‐field gradients and magnetic hyperfine parameters at the metal site were computed with the molecular charge and spin densities obtained and compared with experimental values derived by electron paramagnetic resonance. It was found that the Fermi interaction is critically dependent on the angle between the axial and equatorial CN ligands. © 1995 John Wiley & Sons, Inc.
SINDO1 calculations of vibrational frequencies of adsorbed molecules
Authors: Jug Karl , Ahlswede Bernd , Geudtner Gerald
Published: December 2004

A scaling procedure is used for the force constants generated by the SINDO1 method in internal coordinates to achieve better agreement with experimental frequencies of molecules. The procedure is subsequently used to calculate frequency shifts for adsorbed molecules. The results for CO2 and CO adsorption at NaCl cluster surfaces are in good agreement with experimental data. © 1995 John Wiley & Sons, Inc.
MHD simulations of quadrupolar paleomagnetospheres
Authors: Vogt J. , Zieger B. , Stadelmann A. , Glassmeier K.‐H. , Gombosi T. I. , Hansen K. C. , Ridley A. J.
Published: December 2004

During geomagnetic polarity transitions the Earth's internal magnetic field is expected to deviate significantly from the dipolar configuration observed today, and higher‐order multipoles can become important. Their effects on the magnetosphere are investigated in this study by means of MHD simulations. We look at quadrupolar configurations and vary the parameters that are expected to be most important in determining the large‐scale current systems and the field line topology of such paleomagnetospheres, namely, (1) the orientation of the internal field as well as (2) the orientation of the interplanetary magnetic field (IMF) with respect to the solar wind flow, and (3) the quadrupole shape parameter which controls the topology of the internal field. Zero IMF conditions yield reference cases which allow to locate the magnetopause that otherwise can be obscured by field line merging. Magnetopause currents and cross‐tail currents in quadrupolar configurations are contrasted with the tail current system in the present‐day dipolar magnetosphere. Interplanetary magnetic fields with a nonzero component perpendicular to the solar wind flow are found to have a much stronger effect on the global magnetospheric configuration than a purely parallel or antiparallel IMF. Since a quadrupole field is more structured than a dipole field, conditions that favor field line merging at the dayside are met regularly in quadrupolar magnetospheres. Solar wind‐magnetosphere coupling triggered by reconnection should thus be persistent rather than strongly controlled by solar wind parameters. The investigation presented in this report is part of a multi‐institutional collaboration to model the effects of geomagnetic polarity transitions on the Earth's environment in space and the upper and middle atmosphere.
Climatic shift in patterns of shallow clouds over the Amazon
Authors: Chagnon F. J. F. , Bras R. L. , Wang J.
Published: December 2004

The Amazon rain forest has experienced dramatic changes in the past 50 years due to active deforestation. As of 2001, 15% of the 4,000,000 km2 Brazilian Amazon has been deforested [Instituto Nacional de Pesquisas Espaciais (INPE), 2003]; each year, agricultural exploitation claims an estimated 13,000 km2 of tropical forest [Achard et al., 2002]. In this paper we investigate the climatic effects caused by the observed change of the physical characteristics of the land surface (i.e., increased surface albedo, decreased root‐zone depth, decreased surface roughness and decreased leaf‐area index). More precisely, we examine the spatial correspondence of shallow cumulus clouds with deforestation. Through the creation of an 8‐year record of thrice daily shallow cumulus cloud cover at 1 km resolution from multi‐spectral satellite imagery, we quantitatively show the existence of a significant climatic shift in shallow cloudiness patterns associated with deforestation. This shift manifests itself as an enhancement of shallow cumuli over deforested patches, and has potentially important climatic, hydrologic and ecological implications.
Numerical and observational estimates of Indian Ocean Kelvin wave intrusion into Lombok Strait
Authors: Syamsudin Fadli , Kaneko Arata , Haidvogel Dale B.
Published: December 2004

The merged TOPEX/POSEIDON and ERS‐1/2 altimeter data from 1993 through 2001 and the Spectral Element Ocean Model (SEOM) have been used to investigate Indian Ocean Kelvin waves (IOKWs), specifically their propagation and energy intrusion into Lombok Strait. The altimeter data show the frequent occurrence of IOKWs in either April/May or November/December for the years of 1993–2001 (except 1994) with intraseasonal wave periods (phase speeds) ranging from 35 (1.5) to 90 days (2.9 ms−1). From the altimeter data, it is estimated that 55.6 ± 13.9% of the incoming IOKW energy enters Lombok Strait. The SEOM results indicate an energy intrusion rate of 65%, showing good agreement with the altimeter data. The majority of the incoming IOKW energy is used to increase Kelvin wave energy entering Lombok Strait. This suggests that Lombok Strait acts as a significant transition point for Kelvin wave energy from the Indian Ocean to the internal Indonesian Seas.
Regional probabilities of precipitation change: A Bayesian analysis of multimodel simulations
Authors: Tebaldi C. , Mearns L. O. , Nychka D. , Smith R. L.
Published: December 2004

Tebaldi et al. [2005] present a Bayesian approach to determining probability distribution functions (PDFs) of temperature change at regional scales, from the output of a multi‐model ensemble, run under the same scenario of future anthropogenic emissions. The main characteristic of the method is the formalization of the two criteria of bias and convergence that the REA method [Giorgi and Mearns, 2002] first quantified as a way of assessing model reliability. Thus, the General Circulation Models (AOGCMs) of the ensemble are combined in a way that accounts for their performance with respect to current climate and a measure of each model's agreement with the majority of the ensemble. We apply the Bayesian model to a set of transient experiments under two SRES scenarios. We focus on predictions of precipitation change, for land regions of subcontinental size. We highlight differences in the PDFs of precipitation change derived in regions where models find easy agreement, and perform well in simulating present day precipitation, compared to regions where models have large biases, and/or their future projections disagree. We compare results from the two scenarios, thus assessing the consequences of the two alternative hypotheses, and present summaries based on their averaging.
The shallow plumbing system of Stromboli Island as imaged from 1 Hz instantaneous GPS positions
Authors: Mattia Mario , Rossi Massimo , Guglielmino Francesco , Aloisi Marco , Bock Yehuda
Published: December 2004

The Stromboli volcano (Aeolian Islands, Italy) erupted suddenly on 28 December 2002 after a 17‐year period of typically persistent but moderate eruptive activity, followed two days later by a tsunamigenic landslide on its NW flank (Sciara del Fuoco) felt in the coastal areas of southern Italy. Three continuous GPS stations were quickly deployed near the volcano's rim sampling at 1 Hz, with instantaneous positions computed relative to a fourth station on its flank. We report on two deformation episodes. A vent migration on 16–17 February 2003 caused significant displacements at only one site and contributed to the decision not to issue a warning of an impending tsunamigenic landslide. The second episode on 5 April 2003, a paroxystic explosion from the summit crater, allowed us to model, for the first time with geodetic data, the shallow magma chambers that give rise to Strombolian explosive activity.
Middle to late Holocene changes of the Okhotsk Sea Intermediate Water and their relation to atmospheric circulation
Authors: Itaki Takuya , Ikehara Ken
Published: December 2004

High abundance of the radiolarian Cycladophora davisiana in the Sea of Okhotsk has been observed at the Okhotsk Sea Intermediate Water (OSIW). This water is formed by brine rejection in the polynya and is characterized by cold, oxygenated conditions, with high a microbial content. The C. davisiana abundance recorded in three sediment cores from the southwestern part of the sea implies ventilation changes of the OSIW during the last 7.5 kyrs. The ventilation had significantly increased during the interval from 7.5 to 3.5 ka corresponding to a warm period, but declined during 3 to 2 ka and at 0.3–0.4 ka coincident with cold periods such as the Neoglaciation and Little Ice Age, respectively. The declined ventilation might be caused by reduction of the polynyas with the wind vector change from a northerly to an easterly direction relating to the southward shift of the Aleutian Low during the strong winter.
Comment on “Improved inversion for seismic structure using transformed, S‐wavevector receiver functions: Removing the effect of the free surface” by Anya Reading, Brian Kennett, and Malcolm Sambridge
Authors: Svenningsen Lasse , Jacobsen Bo Holm
Published: December 2004

Reading et al. [2003] propose a transformation which takes the rectangular coordinate system ZRT to the ‘skew’ PSH system. The transformation isolates P‐, SV‐ and SH‐waves of same slowness on the P‐, S‐ and H‐component, respectively, and removes the free surface effect. We have the following comments to their article: A) The transformation matrix in their paragraph has misprints propagated to the text in their Figure 1c. B) The LQT rotation [Vinnik, 1977] has no leakage of P‐displacement into the Q‐component, although a minor SV‐leakage is present on the L‐component. C) The differences between PSH‐ and ZRT‐receiver functions are large, whereas the differences between PSH‐ and LQT‐receiver functions are very small in theory and hardly ever significant in practice.
Relationship of the onset of equatorial F region irregularities with the sunset terminator observed with the Equatorial Atmosphere Radar
Authors: Yokoyama T. , Fukao S. , Yamamoto M.
Published: December 2004

The relationship between sunset terminators and the onset of radar backscatter plumes associated with equatorial spread F (ESF) observed with the 47‐MHz Equatorial Atmosphere Radar from October 2002 to April 2004 is discussed. Almost all irregularity echoes began to appear at or before sunset time at the altitude of the apex of the geomagnetic field line connected with the observed area, and the onset time of more than half of the events corresponded exactly to apex sunset time. This tendency should be due to two causes: (1) the rapid change of the evening zonal electric field and (2) damping of 3‐m scale irregularities by the solar radiation before the apex sunset.
Greenland Ice Sheet: Increased coastal thinning
Authors: Krabill W. , Hanna E. , Huybrechts P. , Abdalati W. , Cappelen J. , Csatho B. , Frederick E. , Manizade S. , Martin C. , Sonntag J. , Swift R. , Thomas R. , Yungel J.
Published: December 2004

Repeated laser‐altimeter surveys and modelled snowfall/summer melt show average ice loss from Greenland between 1997 and 2003 was 80 ± 12 km3 yr−1, compared to about 60 km3 yr−1 for 1993/4–1998/9. Half of the increase was from higher summer melting, with the rest caused by velocities of some glaciers exceeding those needed to balance upstream snow accumulation. Velocities of one large glacier almost doubled between 1997 and 2003, resulting in net loss from its drainage basin by about 20 km3 of ice between 2002 and 2003.
On the relation between solar wind, pseudobreakups, and substorms
Authors: Kullen A. , Karlsson T.
Published: December 2004

A statistical study of pseudobreakups and substorms is performed using Polar UV images from a 3‐month period in winter 1998–1999. Data from the ACE solar wind monitor are examined in order to determine the influence of solar wind parameters on the occurrence of different substorm and pseudobreakup types. The results confirm that the IMF clock angle and the amount of solar wind energy flux control the strength of a substorm. The majority of large substorms appear when the IMF is strongly southward and the solar wind energy flux is high. Most small substorms occur during weakly positive or zero IMF Bz and low solar wind energy flux values. Pseudobreakups are associated with even lower energy fluxes than small substorms and appear typically for weakly positive IMF Bz. These results are in agreement with the scenario that pseudobreakups essentially are very weak substorms. Pseudobreakups appear during quiet times and during the growth phase or the recovery phase of weak or medium strong substorms. Time periods of enhanced geomagnetic activity with recurrent substorms are devoid of pseudobreakups. A detailed analysis of the different pseudobreakup types reveals that quiet time pseudobreakups appear predominantly during northward IMF. At least 20 percent of these appear at the poleward oval boundary. Optically, they do not differ much from very weak substorms. Growth phase pseudobreakups develop typically at the end of a 1 to 2 hour long excursion from northward to weakly southward IMF and are followed by quite weak substorms. A large majority of recovery phase pseudobreakups occur at a strongly polewardly displaced oval boundary at the end of a very active recovery phase. A considerable decrease of the polar cap size during the preceding substorm is connected to a northward turning of the IMF.
Cusp and LLBL as sources of the isolated dayside auroral feature during northward IMF
Authors: Chang S.‐W. , Gallagher D. L. , Spann J. F. , Mende S. B. , Greenwald R. A. , Newell P. T.
Published: December 2004

An intense dayside proton aurora was observed by Imager for Magnetopause‐to‐Aurora Global Exploration Far Ultra‐Violet imager (IMAGE FUV) for an extensive period of northward interplanetary magnetic field (IMF) on 17 and 18 September 2000. This aurora partially coincided with the auroral oval and intruded farther poleward into the polar cap, and it showed longitudinal motions in response to IMF By variation. Intense magnetosheath‐like electron and ion precipitations have been simultaneously detected by Defense Meteorological Satellite Program (DMSP) above the poleward portion of the high‐latitude dayside aurora. They resemble the typical plasmas observed in the low‐altitude cusp. However, less intense electrons and more energetic ions were detected over the equatorward part of the aurora. These plasmas are closer to the low‐latitude boundary layer (LLBL) plasmas. Under strongly northward IMF, global ionospheric convection derived from Super Dual Auroral Radar Network (SuperDARN) radar measurements showed a four‐cell pattern with sunward convection in the middle of the dayside polar cap and the dayside aurora corresponded to two different convection cells. This result further supports two source regions for the aurora. The cusp proton aurora is on open magnetic field lines convecting sunward whereas the LLBL proton aurora is on closed field lines convecting antisunward. These IMAGE, DMSP, and SuperDARN observations reveal the structure and dynamics of the aurora and provide strong evidence for magnetic merging occurring at the high‐latitude magnetopause poleward from the cusp. This merging process was very likely quasi‐stationary.
Mechanism of the magnetic susceptibility enhancements of the Chinese loess
Authors: Liu Qingsong , Jackson Michael J. , Banerjee Subir K. , Maher Barbara A. , Deng Chenglong , Pan Yongxin , Zhu Rixiang
Published: December 2004

Chinese loess/paleosol sequences have been regarded as excellent continental archives for encoding continuous paleoclimatic variations over the past 2.5 Myr. However, the mechanism for magnetic enhancements (especially the low‐field mass‐specific magnetic susceptibility, χ) of Chinese paleosols is still not completely resolved. This study quantifies contributions of aeolian and pedogenic magnetic particles to the bulk magnetic properties of the Chinese loess/paleosols by using a magnetic extraction technique. Magnetic properties of magnetic separates (extractable) and the corresponding residues (nonextractable) for five characteristic samples covering both loesses and paleosols were comprehensively investigated by hysteresis loops, frequency and low‐temperature dependence of magnetic susceptibility, and interparametric ratios. Results show that (1) with moderate degrees of pedogenesis (χ < 10 × 10−7 m3 kg−1), χ is enhanced more by increased concentration of stable single domain (SD) magnetic particles than by viscous superparamagnetic (SP) particles. For more mature paleosols with χ > (10–12) × 10−7 m3 kg−1, contributions of pedogenically related fine‐grained pseudosingle‐domain (PSD, ∼100 nm to several microns) particles become significant; (2) pedogenic particles have a narrow grain size distribution concentrated above the SP/SD threshold; and (3) anhysteretic remanent magnetization (ARM) is carried dominantly by SD grains. Moreover, we propose that only the nonextractable fraction of χ, saturation magnetization (Ms) and remanent magnetization (Mrs) show a strong relationship with the degree of pedogenesis. This new interpretation of magnetic enhancements helps us to retrieve more accurate and quantitative paleoclimatic signals recorded by the Chinese loess/paleosol sequences.
Ocean‐to‐shelf signal transmission: A parameter study
Authors: Huthnance John M.
Published: December 2004

Oceanic signal transmission onto and across the continental shelf to the coast is investigated, focusing on pressure and surface elevation. The model used represents a uniform cross‐slope section on an “f‐plane” with stratification, along‐shelf wave number, and oscillatory frequency. (Inclusion of “beta” and probably a fully three‐dimensional numerical model would be necessary to treat all forms of oceanic signal.) At the model's oceanic boundary, care is needed for the prescription of the oceanic signal to be physically realistic. Then substantial transmission across the slope and shelf is limited to (1) large response near a dispersion relation for a coastal‐trapped wave and (2) large along‐shelf scale relative to a frictional‐decay distance for coastal‐trapped mode 1; that is, friction aids signal transmission. As a consequence, coastal gauges are likely to be effective monitors of only the largest‐scale oceanic motion (typically thousands of kilometers).
A numerical study on the propagation and evolution of resonant interacting gravity waves
Authors: Zhang Shao Dong , Yi Fan
Published: December 2004

Starting from the nonrotating, fully nonlinear basic atmospheric kinetic equations, the nonlinear propagation and evolution of resonant interacting gravity wave packets with small initial amplitudes in a two‐dimensional compressible atmosphere have been simulated. The complete nonlinear resonant interaction process of the gravity wave packets is exhibited. The numerical results show that a downward propagating gravity wave is excited by two up‐going gravity waves initially due to the resonant interaction, and the wavelength of the excited gravity wave decreases with time. During the whole nonlinear propagation and evolution, although the total wave energy for the interacting triad is almost conservative, obvious wave energy exchange among the three interacting gravity waves is observed. Wave energy tends to transfer from the wave with larger amplitude to that with smaller amplitude, and this energy transfer trend seems to be independent of the initial wave energies of the interacting waves. A detailed numerical analysis shows that when a gravity wave is excited by resonant interaction, its energy continuously grows up from 0 J to a considerable level (5.44 × 105 J). This process is irreversible rather than periodic and will be finished within a characteristic time (15 hours for the presented case). More simulation examples are also carried out to study the effects of the small initial amplitudes and wavelengths on the energy exchange, which shows that although the characteristic time is not sensitive to the small initial amplitudes, it depends on the wavelengths, and both the initial amplitudes and wavelengths can affect the net wave energy exchange of the resonant interaction.
On the distribution of ozone in stratospheric anticyclones
Authors: Harvey V. L. , Pierce R. B. , Hitchman M. H. , Randall C. E. , Fairlie T. D.
Published: December 2004

Twelve years (1991–2003) of satellite occultation ozone data are combined with a climatology of stratospheric anticyclones and polar vortices to quantify the climatological ozone differences between air mass types. Ozone data from the Stratospheric Aerosol and Gas Experiment (SAGE) II, the Halogen Occultation Experiment (HALOE), the Polar Ozone and Aerosol Measurement (POAM) II and III missions, and the Improved Limb Atmospheric Spectrometer (ILAS) sensor are used in this study. Daily ozone measurements in the 400–1600 K altitude range are categorized as being either (1) in an anticyclone, (2) in a polar vortex, or (3) in neither (hereinafter referred to as “ambient”). Monthly mean ozone is then calculated in each air mass category from data combined over all years. This study focuses on ozone differences between anticyclones and the ambient environment. A composite annual cycle of ozone in ambient regions is compared to ozone in anticyclones as a function of altitude and latitude. Ozone differences result from both anomalous transport and photochemistry in the vicinity of stratospheric anticyclones. The relative importance of transport versus chemistry is inferred from the long‐term ozone anomalies observed here. In summer, ozone gradients between different air mass types are small. In other seasons, results indicate three distinct vertical regimes at high latitudes. Below ≈600 K, anticyclones coincide with regions where ozone is reduced by 10–50% during the winter. Between 600 and 900 K from fall to midwinter, anticyclones are associated with ≈10% more ozone than ambient air masses. Positive ozone anomalies are also observed in low‐latitude anticyclones within this vertical layer; however, they are half the size of their high‐latitude counterparts and peak several months later. Above 900 K the abundance of ozone in anticyclones is ≈10% less than in the surrounding air. This upper stratospheric regime results from the formation of “low‐ozone pockets” (LOPs) in stratospheric anticyclones. All LOPs that formed between November 1991 and November 2003 and were observed by a satellite used in this study (108 pockets) are documented here in the most comprehensive catalog of LOPs to date.
Amended biochemical characteristics and phylogenetic position of Treponema medium
Authors: Nakazawa F. , Hoshino E. , Fukunaga M. , Jinno T. , Asai Y. , Yamamoto H. , Ogawa T.
Published: December 2004

Umemoto et al. (1997, Int J Syst Bacteriol 47, pp. 67–72) proposed spirochete strain G7201, isolated from the periodontal pocket of an adult patient, as a new species, Treponema medium. They deposited this strain in the American Type Culture Collection (ATCC) as type strain ATCC 700293T. Recently, ATCC suggested that there is a discrepancy between the previous report and the results obtained by ATCC in biochemical tests on T. medium ATCC 700293T. In this study, we re‐examined and verified the biochemical characteristics of T. medium. The fermentation pattern of carbohydrates of T. medium resembled that of Treponema vincentii and Treponema denticola, but T. medium was clearly differentiated from T. vincentii in the production of indole, and from T. denticola in the hydrolysis of esculin. Also, sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS‐PAGE) protein profile analysis and phylogenetic comparison of 16S rDNA sequences revealed that T. medium is clearly differentiated from any established treponemal species, which supports the validity of the proposal of Treponema medium as a new species.
Concurrent oral shedding of feline calicivirus and feline herpesvirus 1 in cats with chronic gingivostomatitis
Authors: Lommer M. J. , Verstraete F. J. M.
Published: December 2004

Oral mucosal salivary samples were collected from 25 cats with chronic gingivostomatitis and 24 cats with periodontal disease. Viral culture and isolation of feline calicivirus and feline herpesvirus 1 were performed. Eighty‐eight per cent of cats with chronic gingivostomatitis were shedding both viruses, compared to 21% of cats without chronic oral inflammatory disease. Cats with chronic gingivostomatitis are significantly more likely to concurrently shed both feline calicivirus and feline herpesvirus 1 than are cats with classical periodontal disease.
Prevalence of Csh‐like fibrillar surface proteins among mitis group oral streptococci
Authors: Elliott D. , Harrison E. , Handley P. S. , Ford S. K. , Jaffray E. , Mordan N. , McNab R.
Published: December 2004

The prevalence of Csh‐like fibrillar surface proteins among oral streptococci was investigated by ELISA and by immunoelectron microscopy using antiserum raised to recombinant fragments of CshA of Streptococcus gordonii DL1. The majority of S. gordonii, Streptococcus sanguis and Streptococcus oralis strains tested elaborated short (ca. 50–80 nm long) surface fibrils and reacted with antiserum to the amino acid repeat region of CshA, demonstrating the widespread nature of Csh‐like proteins among these species. In contrast, reactivity with antiserum raised to the adhesion‐mediating non‐repetitive region of CshA was more restricted. On the basis of the ELISA results, several isolates were selected for immunogold analysis using CshA antisera. Immunogold‐negative staining showed a surface distribution of 10 nm gold particles consistent with antibody binding to short fibrils. Long fibrils (>150 nm long), where present, were not significantly labelled with gold. The results suggest that some of the short peritrichous fibrils on many mitis group streptococci comprise Csh‐like fibrillar protein. Further, the data are consistent with our hypothesis that the antigenically conserved amino acid repeat region of Csh‐like proteins forms a scaffold for cell‐distal presentation of the amino‐terminal non‐repetitive region that, at least in S. gordonii DL1, functions as an adhesin.
Activation of interleukin 1β gene transcription by human cytomegalovirus: molecular mechanisms and relevance to periodontitis
Authors: Wara‐aswapati N. , Boch J. A. , Auron P. E.
Published: December 2004

In recent years, studies have demonstrated an association between human cytomegalovirus (HCMV) and destructive periodontal disease. It has been shown that reactivation of HCMV in periodontitis lesions may be related to progressing periodontal disease. Several possible mechanisms by which HCMV exerts periodontopathic potential have been previously proposed. These are reviewed and include the upregulation of bone resorptive cytokines such as interleukin‐1beta (IL‐1β) and tumor necrosis factor‐alpha (TNF‐α) by active HCMV infection at the periodontitis site. This review focuses on the molecular basis of IL‐1β gene activation by HCMV immediate early (IE) gene products. A novel hypothesis is also described whereby HCMV plays a significant role in the pathogenesis of periodontal disease by the ability of its IE proteins to strongly transactivate IL‐1β gene expression. More studies are needed to further explore this hypothesis and clarify the association between HCMV and periodontitis.
Acid‐neutralizing activity during amino acid fermentation by Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum
Authors: Takahashi N.
Published: December 2004

Acid‐neutralizing activity during amino acid fermentation by washed cells of Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum was studied. When the washed cells of these strains were anaerobically incubated in the presence of aspartylaspartic acid or glutamylglutamic acid for P. gingivalis, aspartic acid for P. intermedia and glutamic acid for F. nucleatum at an initial pH of 5.0 or 5.5, the pH of the incubation mixtures rose toward neutral. F. nucleatum had the highest acid‐neutralizing activity, followed by P. intermedia and P. gingivalis. The P. intermedia and F. nucleatum cells were used to measure the amounts of base produced at a fixed pH of 5.0. These cells generated significant amounts of base at pH 5.0 along with the production of organic acids and ammonia from aspartic or glutamic acid. Acid–base balance theoretically calculated from the amounts of consumed substrate and end products implies that the acid‐neutralizing activity was derived from the decrease in acidity during the fermentation of amino acid into organic acids and ammonia.
Detection of Filifactor alocis in endodontic infections associated with different forms of periradicular diseases
Authors: Siqueira J. F. , Rôças I. N.
Published: December 2004

Recent molecular studies have expanded the list of suspected endodontic pathogens. The aim of this study was to evaluate the occurrence of Filifactor alocis in primary endodontic infections associated with different forms of periradicular diseases. Identification by nested polymerase chain reaction was performed in root canal samples from teeth associated with either asymptomatic periradicular lesions or acute apical periodontitis. Samples were also taken by aspiration of purulent exudate associated with acute apical abscesses. DNA extracted from the samples was initially amplified using universal 16S rDNA primers followed by a second round of amplification using the first PCR products to detect a specific fragment of F. alocis 16S rDNA. F. alocis was detected in 12/21 (57.1%) root canal samples from teeth showing asymptomatic periradicular lesions and in 3/10 (30%) samples taken from root canals associated with acute apical periodontitis. This species occurred in 8/19 (42.1%) pus aspirates obtained from abscessed teeth. In general, F. alocis was detected in 23/50 (46%) samples taken from endodontic infections. These findings suggest that F. alocis is involved in the etiology of different forms of periradicular diseases and has the potential to be an endodontic pathogen.