bluuebunny/crossref_metadata_2025 huggingface dataset:
On multireference superdirect configuration interaction in third order
Authors: Duch Włodzisław , Meller Jarosław
Published: December 2004

The superdirect configuration interaction (Sup‐CI) method has the usual versatility and stability of the CI methods with computational efficiency typical to that of the many‐body methods, such as the many‐body perturbation theory (MBPT). The Hamilton operator is projected into a space of a few trial vectors, such as Krylov, Nesbet, or Møller–Plesset correction vectors. In this space, Hamiltonian matrix elements may be directly computed in the many‐body fashion, as weighted sums of integral products over orbital indices. The variation‐perturbation method based on the first‐order wave function is equivalent to the Sup‐CI method with a single correction vector of the Møller–Plesset type. Different points of view on the superdirect CI method are discussed and a version in which third‐order contributions are computed for a relatively small (10–100) space of reference and correction vectors is tested. Selection of the best “effective first‐order spaces” and size‐extensivity corrections in Sup‐CI are briefly discussed. Møoller–Plesset, Epstein–Nesbet, and other correction vectors are included in the model calculations on the symmetric stretch of bonds in water, acetylene, and the NH2 molecule. Errors are almost independent of molecular geometry and the method appears to be superior than the multireference second‐order perturbation methods. © 1994 John Wiley & Sons, Inc.
Second quantization and coefficients of fractional parentage
Authors: Bernotas Andrius , Kaniauskas Julius
Published: December 2004

The coefficients of fractional parentage (CFP), treated by tradition as antisymmetrizing multipliers, do not exist as such in the second‐quantization representation, because, therein, by definition, there is nothing to antisymmetrize. This by no way means that the above‐mentioned representation is less relevant in theoretical atomic spectroscopy than is any other one. On the contrary, all the well‐known mathematical apparatus is still successfully applied, alongside with numerous new useful features. Moreover, the analysis presented here yields some results not so obvious from the point of view of the coordinate representation, namely, the consequent application of the second‐quantization representation led us to an expansion of many‐shell wave functions employing analogs of many‐shell CFP, which appeared to be considerably simpler than the traditional CFP expansion. Also, a generalization of Redmond's formula for the case of many‐shell CFP and a straightforward method of deriving summation rules for products of CFP are clear in the second‐quantization representation and are sketched here. © 1994 John Wiley & Sons, Inc.
Ab initio study of molecular g‐tensors
Authors: Lushington G. H. , Bündgen P. , Grein F.
Published: December 2004

The molecular g‐tensors for the molecules NO2, CO, C3H5, H2CO+, and NF are calculated at the unrestricted Hartree–Fock (UHF) level using the Rayleigh–Schrödinger perturbation approach. All one‐electron terms have been evaluated, including the relativistic mass correction, the one‐electron spin–Zeeman gauge correction, and a second‐order term involving the spin–orbit coupling and the orbital–Zeeman interaction. The relative importance of the first‐order terms is found to be quite substantial. For first‐row molecules, their total contribution is often of the same order of magnitude as of the second‐order contribution, in some instances even larger. A study on the basis‐set dependence of these g‐tensors has been conducted. At this level, the most important basis‐set criterion is shown to be a satisfactory description of the valence regions. Finally, the gauge dependence of these g‐tensor calculations has been systematically studied. This dependence seems to be substantially reduced for basis sets which include polarization functions. © 1995 John Wiley & Sons, Inc.
Discrete variable representation method applied to the determination of J = 0 vibrational bound states of NO2
Authors: Vilanove H. , Jacon M.
Published: December 2004

The discrete variable representation method (DVR) is applied to the calculation of the J = 0 vibrational energy levels of the ground electronic state of nitrogen dioxide, a molecule which shows a large amplitude bending vibration. The Hamiltonian is expressed in Johnson hyperspherical coordinates and developed on a DVR basis set for each coordinate. A successive diagonalization–truncation method is applied which gives accurate values for the energy levels up to ≃ 7000 cm−1. © 1995 John Wiley & Sons, Inc.
Distribution of convective Lower Halocline Water in the eastern Arctic Ocean
Authors: Kikuchi Takashi , Hatakeyama Kiyoshi , Morison James H.
Published: December 2004

We investigate the distribution of convectively formed Lower Halocline Water (cLHW) in the eastern Arctic Ocean using observational and climatological data. The cLHW can be defined as the water mass in the cold halocline layer formed by winter convection. The presence of cLHW is indicated by temperatures close to the freezing point and a sharp bend in the Θ‐S curve near the salinity of cLHW. Results from ice‐drifting buoy observations in 2002 show differences in water mass characteristics in the upper ocean among the Amundsen Basin, over the Arctic Mid‐Ocean Ridge, and in the Nansen Basin. In 2000–2002, cLHW was present over the Arctic Mid‐Ocean Ridge and the Nansen Basin, but was largely absent from the Amundsen Basin. Using climatological data, we find that cLHW was confined to the Nansen Basin prior to 1990. In the early 1990s, cLHW still covered only the Nansen Basin, but extended to the northern side of the Arctic Mid‐Ocean Ridge in the mid‐1990s and covered the whole of the Amundsen Basin by the late 1990s. In the early 2000s, the area of cLHW moved back to its present boundary on the northern side of the Arctic Mid‐Ocean Ridge. These results correspond roughly to other changes in the Arctic Ocean circulation and water mass structure, but with a time delay. We hypothesize that general circulation changes and the cutoff of source water for advective‐convective modification of the LHW are causes of the change in cLHW distribution. The lag in changes to cLHW distribution behind other changes in the atmosphere and upper ocean are likely related to differences in circulation change with depth and the transit time from cLHW formation.
A mean dynamic topography computed over the world ocean from altimetry, in situ measurements, and a geoid model
Authors: Rio M.‐H. , Hernandez F.
Published: December 2004

The lack of an accurate geoid still prevents precise computation of the ocean absolute dynamic topography from satellite altimetry and only sea level anomalies (SLA) can be accurately deduced. In the new context of Global Ocean Data Assimilation Experiment (GODAE) where models are assimilating satellite altimetry, the estimation of a realistic mean dynamic topography (MDT) consistent with SLA is a crucial issue. In a first “direct” approach, a MDT is computed by subtracting the geoid model EIGEN‐2 from the Mean Sea Surface Height CLS01, determined from 7 years of altimetric data (TOPEX and ERS1,2) at spherical harmonic degree 30. To provide the scales shorter than 660 km, the Levitus climatology is merged with the resulting MDT, both weighted by their respective errors. This solution provides a “first guess” for the computation of a global and higher resolution MDT. Then, a “synthetic” technique is used to combine in situ measurements and altimetric data: TOPEX and ERS1,2 altimetric anomalies are subtracted from in situ measurements of the full dynamical signal (based on buoy velocities from the WOCE‐TOGA program and XBT, CTD casts). The resulting values provide local estimates of the mean field, in terms of currents or dynamic topography, which are used to improve the first guess using an inverse technique. The MDT obtained is compared to other mean dynamic fields, and a verification using independent in situ data shows improvements in most areas. It exhibits a more energetic representation of the subtropical and subpolar gyres; sea level gradients associated with the main currents are strongly enhanced. Differences with independent velocity observations are globally lower than 13 cm/s rms.
Biogeochemical impact of summertime coastal upwelling on the New Jersey Shelf
Authors: Glenn Scott , Arnone Robert , Bergmann Trisha , Bissett W. Paul , Crowley Michael , Cullen Jay , Gryzmski Joe , Haidvogel Dale , Kohut Josh , Moline Mark , Oliver Mathew , Orrico Cris , Sherrell Robert , Song Tony , Weidemann Alan , Chant Robert , Schofield Oscar
Published: December 2004

The alternative hypothesis that observed regions of recurrent hypoxia on the New Jersey inner shelf are more related to coastal upwelling than riverine inputs of nutrients was investigated through a series of multidisciplinary research programs beginning in 1993. The largest variations in ocean temperatures along the New Jersey coast, other than seasonal, are found to be caused by episodic summertime upwelling events driven by southwesterly winds associated with the atmospheric Bermuda High. Off the southern coast of New Jersey, topographic variations associated with ancient river deltas cause upwelled water to evolve into an alongshore line of recurrent upwelling centers that are colocated with historical regions of low dissolved oxygen. Recurrent upwelling centers are observed every summer in a 9‐year data set. The most significant upwelling events occur in summers following colder than usual falls and winters. Size and duration of individual events are correlated and are found to depend on the wind forcing history that effects the inner side of the Middle Atlantic Cold Pool, the precipitation history that effects the strength of the Hudson River plume, and the mixing storm frequency. Upwelling results in a significant enhancement of particulate organic carbon. The typical carbon enhancement associated with the upwelling is sufficient to deplete 75% of the oxygen in the bottom water, making it borderline hypoxic. This indicates that topographically controlled coastal upwelling, rather than riverine inputs, is the more probable mechanism for generating the historical regions of recurrent hypoxia observed along the New Jersey coast.
Seismic anisotropy in the lower mantle: A comparison of waveform splitting of SKS and SKKS
Authors: Niu Fenglin , Perez Anisa M.
Published: December 2004

We have carried out a global investigation on seismic anisotropy in the lower mantle by comparing the waveform splitting of SKS and SKKS found at the same seismogram. The two shear waves have very similar ray paths in the upper mantle but different ones in the lower mantle. We collected a total of 104 SKS+SKKS waveform data recorded at 76 stations. The SKS+SKKS data are first matched with a single anisotropic model (2 parameters: the fast polarization direction ϕ and delay time δt) and two independent anisotropic models (4 parameters). We then applied an F‐test to examine whether the 4‐parameter models are better than the 2‐parameter ones based on error improvement. We found that the data from most of the stations can be explained by the simple 2‐parameter models. While this observation provides compelling evidence that the vast part of the lower mantle below ∼1000 km (including the D” region) is transversely isotropic, it is still arguable that the uppermost lower mantle and the transition may partly contribute the SKS/SKKS splittings. We also found that the 4‐parameter models provide a better fitting to the SKS and SKKS splitting at 8 stations, suggesting the existence of transverse anisotropy or anomalous dipping structures in some part of the lower mantle.
Non‐linear deformation and break up of enclaves in a rhyolitic magma: A case study from Lipari Island (southern Italy)
Authors: Holtz Francois , Lenné Sascha , Ventura Guido , Vetere Francesco , Wolf Philipp
Published: December 2004

A dome from Lipari Island (Southern Italy) consists of 12 vol.% of circular, elongated and folded latitic enclaves hosted in a rhyolitic matrix. The dm‐ to cm‐scale enclaves are more deformed than the mm‐scale blobs. The critical value of the ratio between the viscous forces, which allow deformation and eventually break up blobs of latitic magma, and the interfacial tension forces is larger than 0.29. The Reynolds number is <5.3. The equivalent radius and the axial ratio of the enclaves follow power‐law distributions. This feature suggests that the break up and stretching of magmas are non‐linear, scale‐invariant, probably cyclic processes. The coexistence of enclaves of different shape and the self‐similar size distributions suggest that chaotic advection plays a major role in the formation of mingled magmas. Caution must be used when measuring the finite strain from enclave shapes because they may break apart during the deformation.
Multi‐hop whistler‐mode ELF/VLF signals and triggered emissions excited by the HAARP HF heater
Authors: Inan U. S. , Gołkowski M. , Carpenter D. L. , Reddell N. , Moore R. C. , Bell T. F. , Paschal E. , Kossey P. , Kennedy E. , Meth S. Z.
Published: December 2004

Modulated heating of the lower ionosphere with the HAARP HF heater is used to excite 1–2 kHz signals observed on a ship‐borne receiver in the geomagnetic conjugate hemisphere after propagating as ducted whistler‐mode signals. These 1‐hop signals are believed to be amplified, and are accompanied by triggered emissions. Simultaneous observations near (∼30 km) HAARP show 2‐hop signals which travel to the northern hemisphere upon reflection from the ionosphere in the south. Multiple reflected signals, up to 10‐hop, are detected, with the signal dispersing and evolving in shape, indicative of re‐amplification and re‐triggering of emissions during successive traversals of the equatorial interaction regions.
Modulation of the midlatitude ionospheric E region by atmospheric gravity waves through polarization electric field
Authors: Yokoyama T. , Horinouchi T. , Yamamoto M. , Fukao S.
Published: December 2004

We have studied coupling between the neutral atmosphere and the ionospheric E region in the midlatitude by combining two numerical simulation models. Atmospheric gravity waves generated in the troposphere propagate through the stratosphere and the mesosphere and can reach the lower thermosphere. When a zonal wind shear that can accumulate a sporadic‐E (Es) layer (eastward below and westward above) is applied, the accumulated Es layer is strongly modulated by the gravity waves, and polarization electric field due to the modulated Es layer produces wave‐like patterns of plasma density in the upper E region. Since the eastward wind below the shear node filters out gravity waves with eastward phase velocity, those with westward phase velocity are dominant where the Es layer is accumulated. Because of the angle between phase front of gravity waves and the geomagnetic field line, gravity waves with southward phase velocity is more effective to generate polarization electric field than those with northward phase velocity. Since gravity waves with southwestward phase velocity have phase fronts aligned from northwest to southeast, polarization electric field also has the similar structure. This mechanism can explain the spatial structure of quasi‐periodic (QP) echoes associated with plasma irregularities in the midlatitude E region which often shows northwest‐southeast alignment.
Low‐frequency waves and instabilities in stratified, gyrotropic, multicomponent plasmas: Theory and application to plasma transport in the Io torus
Authors: André N. , Ferrière K. M.
Published: December 2004

We extend our previous study of low‐frequency waves and instabilities in stratified, gyrotropic (with a thermal pressure characterized by P⊥ ≠ P∥), two‐component plasmas to multicomponent plasmas. We then apply our theoretical findings to the plasma transport driven by the interchange instability in the Io torus. Our derivation starts with the correct calculation, from the Vlasov equation, of the contributions from all plasma components to the thermal pressure perturbations of the whole plasma. By incorporating the expressions of the thermal pressure perturbations into the classical system of fluid and electromagnetic equations, we are able to derive the dispersion relation as well as the local stability criterion of low‐frequency modes in stratified, gyrotropic, multicomponent plasmas. Much of our discussion is devoted to the modes on which stratification has a significant impact, i.e., the so‐called quasi‐interchange modes. In a second step, we apply the stability criteria obtained for the quasi‐interchange modes to realistic equatorial distributions of plasma and magnetic field in the Io torus based on the most recent available observational data. We perform this application in order to gain new insights into plasma transport in the torus and compare our results with previous studies on this subject.
Mass transport in the heliosphere by energetic neutral atoms
Authors: Gruntman Mike , Izmodenov Vlad
Published: December 2004

Energetic neutral atoms (ENAs) are recognized as a powerful tool for remote probing of distant hot space plasmas, in particular the plasmas abundant at the heliospheric boundary where the expanding solar wind meets the surrounding local interstellar medium. We show here for the first time that the heliospheric ENAs originating in the heliospheric sheath between the termination shock and the heliopause and reaching the inner heliosphere also provide an important and heretofore unaccounted source of atomic hydrogen in the Sun's vicinity. These ENAs are a major contributor to the density of interplanetary hydrogen at heliocentric distances <1 AU and could dominate in the downwind (interstellar wind) region under typical solar and interstellar conditions. Mass transport by heliospheric ENAs may become especially important for determining the origin of the pickup ions attributed to the inner source of neutral particles in the Sun's vicinity and for characterization of the three‐dimensional solar wind flow by imaging in extreme ultraviolet.
Revisiting the mechanism of reversed thermoremanent magnetization based on observations from synthetic ferrian ilmenite (y = 0.7)
Authors: Lagroix France , Banerjee Subir K. , Moskowitz Bruce M.
Published: December 2004

This study investigates the magnetic behavior of three well‐characterized synthetic single‐phase ferrian ilmenite (y = 0.7) specimens over the temperature range between 10 K and 573 K. Careful experiments measuring induced and remanent magnetizations in variable temperatures, applied magnetic fields, and pretreatment conditions are conducted in order to elucidate the mechanism leading to reversed thermoremanent magnetization (RTRM). Magnetic ordering temperatures of the cation ordered domains, in all three samples, are estimated at 380 K, suggesting that their Curie temperatures (TC) are independent of the sample's thermal history. This is not the case for cation disordered boundaries resulting from quenching from high temperatures. These cation disordered domains have estimated magnetic ordering temperatures of 418 K (Q1300), 410 K (Q1050), and 425 K (Q900). The data unambiguously support a less than perfect ferrimagnetic–antiferromagnetic exchange interaction as the fundamental source of RTRM. Furthermore, the magnetic field strength of the “effective” exchange anisotropies in such polycrystalline samples are estimated at ∼2.7 mT (Q1300), ∼12 mT (Q1050), and 0 mT (Q900). However, from the results presented herein we conclude that favorable conditions for the acquisition of RTRM are dependent not only on the strength of the exchange anisotropy but also on the crucial role played by the size of the cation ordered domains.
Mechanism of the parasitic remanence of aluminous goethite [α‐(Fe, Al)OOH]
Authors: Liu Qingsong , Torrent José , Yu Yongjae , Deng Chenglong
Published: December 2004

The Néel temperature (TN) of cation‐substituted goethites is controlled by the degree of isomorphous substitution and crystal defects. In particular, the exact relationship between the TN of the antiferromagnetism (AFM) and the unblocking temperature (TB) of the parasitic remanence is undetermined. We found that TB is systematically higher than TN for a set of well‐characterized aluminous goethite samples. In addition, the difference between TB and TN increases from ∼8–9 K for a pure goethite (that contains vacancies) to >20 K for Al‐substituted goethites. This indicates that TB and TN change independently with the diamagnetic substitutions, suggesting a fundamental difference of magnetization process between parasitic remanence and AFM. A zonal distribution of the diamagnetic substitutions has been incorporated to account for the observed magnetic properties of the AFM and the parasitic remanence. Nonetheless, both parasitic remanence and AFM could exist along the goethite c axis.
Numerical study of a coastal current on a steep slope in presence of a cape: The case of the Promontorio di Portofino
Authors: Doglioli Andrea M. , Griffa Annalisa , Magaldi Marcello G.
Published: December 2004

A process study aimed at investigating the winter circulation in the area of the Promontorio of Portofino (northwestern Mediterranean) is presented, motivated by historical current measurements suggesting the presence of an attached recirculating eddy in the lee of the Promontorio (cape). A sensitivity study is first performed in an idealized setting, considering the interaction of a steady incoming current with the cape. Numerical experiments are performed using both two‐dimensional (2‐D) (vertically integrated) and 3‐D versions of the POM model. From the 2‐D results, the main controlling parameter appears to be the equivalent Reynolds number Ref, in agreement with previous historical results. In the 3‐D case, the dependence on the vertical Ekman number Ekv is investigated at fixed Ref, and a significant intensification of the attached eddy with respect to the 2‐D solutions is obtained. The main difference between the 2‐D and 3‐D dynamics is the presence of a resolved bottom Ekman layer in 3‐D, introducing a vertical shear in the incoming current, particularly noticeable in the region of the shelf break. This shear is likely to be responsible for a “secondary circulation” (dominated by Coriolis effect), inducing an inshore surface current and associated upwelling in the lee of the cape, and causing the observed eddy intensification. Experiments with realistic bathymetry are performed, and the 3‐D results are found to be in good qualitative agreement with the measurements. The results are expected to be relevant for biological transport, pointing out to a mechanism for eddy intensification connected with surface inshore transport and upwelling.
On the future of carbonaceous aerosol emissions
Authors: Streets D. G. , Bond T. C. , Lee T. , Jang C.
Published: December 2004

This paper presents the first model‐based forecasts of future emissions of the primary carbonaceous aerosols, black carbon (BC) and organic carbon (OC). The forecasts build on a recent 1996 inventory of emissions that contains detailed fuel, technology, sector, and world‐region specifications. The forecasts are driven by four IPCC scenarios, A1B, A2, B1, and B2, out to 2030 and 2050, incorporating not only changing patterns of fuel use but also technology development. Emissions from both energy generation and open biomass burning are included. We project that global BC emissions will decline from 8.0 Tg in 1996 to 5.3–7.3 Tg by 2030 and to 4.3–6.1 Tg by 2050, across the range of scenarios. We project that OC emissions will decline from 34 Tg in 1996 to 24–30 Tg by 2030 and to 21–28 Tg by 2050. The introduction of advanced technology with lower emission rates, as well as a shift away from the use of traditional solid fuels in the residential sector, more than offsets the increased combustion of fossil fuels worldwide. Environmental pressures and a diminishing demand for new agricultural land lead to a slow decline in the amount of open biomass burning. Although emissions of BC and OC are generally expected to decline around the world, some regions, particularly South America, northern Africa, the Middle East, South Asia, Southeast Asia, and Oceania, show increasing emissions in several scenarios. Particularly difficult to control are BC emissions from the transport sector, which increase under most scenarios. We expect that the BC/OC emission ratio for energy sources will rise from 0.5 to as much as 0.8, signifying a shift toward net warming of the climate system due to carbonaceous aerosols. When biomass burning is included, however, the BC/OC emission ratios are for the most part invariant across scenarios at about 0.2.
Mars remote‐sensing analog studies in the Badwater Basin, Death Valley, California
Authors: Baldridge Alice M. , Farmer Jack D. , Moersch Jeffrey E.
Published: December 2004

The search for evaporites on Mars has important implications for the role that liquid water has played in shaping the planet's geologic, climatic, and potential biologic history. Orbital investigations of surface mineralogy are crucial to this exploration effort. With the exception of coarse‐grained gray hematite at a restricted number of sites and trace amounts of carbonate in globally distributed dust deposits, the Thermal Emission Spectrometer (TES) and Thermal Emission Imaging System (THEMIS) instruments have yet to find widespread mineralogical evidence of aqueously formed minerals. This may reflect the coarse spatial resolution of TES (3 × 5 km/pixel) and low spectral resolution of THEMIS (10 bands between 6.5 and 14.5 μm). Spectral mapping in the Badwater Basin, Death Valley, California, was conducted to better understand the capabilities of TES and THEMIS in detecting evaporite minerals. High‐resolution MODIS/ASTER Airborne Simulator (MASTER) data, degraded to TES and THEMIS spatial resolutions, were used to evaluate the detection limits of sulfates and carbonates. To assess the validity of this spectral remote sensing, a quantitative ground truth analysis of surface mineralogy in the Badwater Basin was performed. The analysis was based on thin section petrography, X‐ray diffraction, electron microprobe, and laboratory and field thermal emission spectrometer analyses. Taken together, the results of all five methods provided enough constraints for a robust interpretation that was in general agreement with the spectral remote‐sensing mapping study for ∼90% of the surface samples examined.
Release and fragmentation of aggregates to produce heterogeneous, lumpy coma streams
Authors: Clark B. C. , Green S. F. , Economou T. E. , Sandford S. A. , Zolensky M. E. , McBride N. , Brownlee D. E.
Published: December 2004

The unpredicted heterogeneity in particle number density in the coma of Wild 2 is consistent with delayed fragmentation to produce small particles from larger aggregates initially ejected from the cometary nucleus. The resultant heterogeneous inner coma results in stochastic variations in particle number and size distribution. Fragmentation can be accelerated after aggregate release by enhanced heating and one or more additional factors such as abrupt depressurization, phase transitions, exothermic chemical reactions, centrifugal forces, and electrostatic repulsion. Certain predicted characteristics of such in‐flight disaggregation in coma particle streams correspond to known cometary phenomena.
Poor preservation potential of organics in Meridiani Planum hematite‐bearing sedimentary rocks
Authors: Sumner Dawn Y.
Published: December 2004

Life is composed of organic compounds, and characterizing preserved compounds provides insights into the presence of specific types of life, including early life on Earth. With growing evidence for a wet early Mars, excitement over the potential of an early Martian biosphere strongly motivates Mars exploration. However, the preservation potential of organic compounds in rocks on either Earth or Mars depends critically on mineralogy. Results from elemental, mineralogical, and morphological characterization of sedimentary rocks by the Opportunity rover team in the vicinity of the Challenger Memorial Station, Meridiani Planum, demonstrate an abundance of Fe(III) and sulfate minerals that formed from liquid water. The composition of these sedimentary rocks suggests that organic compounds are unlikely to be preserved within them, even if present when the rocks were deposited, based on comparisons with iron formation, acid lake deposits, and iron‐containing concretions from Earth. No evidence consistent with the presence of organic compounds, such as the presence of Fe(II) minerals, has been reported from Meridiani Planum to date. Thus these Martian sedimentary rocks are not a good target to explore for organic compounds on Mars.
Threshold phenomena in erosion driven by subsurface flow
Authors: Lobkovsky Alexander E. , Jensen Bill , Kudrolli Arshad , Rothman Daniel H.
Published: December 2004

We study channelization and slope destabilization driven by subsurface (groundwater) flow in a laboratory experiment. The pressure of the water entering the sand pile from below as well as the slope of the sand pile are varied. We present quantitative understanding of the three modes of sediment mobilization in this experiment: surface erosion, fluidization, and slumping. The onset of erosion is controlled not only by shear stresses caused by surfical flows but also by hydrodynamic stresses deriving from subsurface flows. These additional forces require modification of the critical Shields criterion. Whereas surface flows alone can mobilize surface grains only when the water flux exceeds a threshold, subsurface flows cause this threshold to vanish at slopes steeper than a critical angle substantially smaller than the maximum angle of stability. Slopes above this critical angle are unstable to channelization by any amount of fluid reaching the surface.
Bacteria‐binding plasma proteins in pellicles formed on hydroxyapatite in vitro and on teeth in vivo
Authors: Carlén A. , Rüdiger S. G. , Loggner I. , Olsson J.
Published: December 2004

Previous studies on dental pellicle formation and bacterial adherence have focussed on saliva and its components. The tooth surface is, however, also exposed to the plasma‐derived crevicular fluid. In the present study, (i) plasma proteins in in vitro and in vivo pellicles were examined using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE), immunoblotting and image analysis and (ii) the adherence of periodontopathogenic bacteria to experimental plasma and saliva pellicles was examined using radio‐labelled bacteria and liquid scintillation counting. The plasma components fibrinogen, fibronectin, albumin and IgG were incorporated from plasma in the experimental pellicle and mediated the adherence of Porphyromonas gingivalis, Fusobacterium nucleatum and Actinomycesnaeslundii. These proteins were also readily detected in in vivo pellicles and were found to a higher extent in pellicles formed at the gingival part of the tooth surface than at the incisal part.
Defensin‐induced adaptive immunity in mice and its potential in preventing periodontal disease
Authors: Brogden K. A. , Heidari M. , Sacco R. E. , Palmquist D. , Guthmiller J. M. , Johnson G. K. , Jia H. P. , Tack B. F. , McCray P. B.
Published: December 2004

The severity of periodontal disease is dependent on a combination of host, microbial agent and environmental factors. One strong correlate related to periodontal disease pathogenesis is the immune status of the host. Here we show that human neutrophil peptide (HNP) defensins or human β‐defensins (HBD), co‐administered intranasally with the antigen ovalbumin (OVA), induce unique immune responses that if used with microbial antigens may have the potential to hinder the pathogenesis of periodontal disease. C57BL/6 mice were immunized intranasally with phosphate buffered saline (PBS) containing 1 µg HNP‐1, HNP‐2, HBD1 or HBD2 with and without 50 μg OVA. At 21 days, isotypes and subclasses of OVA‐specific antibodies were determined in saliva, serum, nasal wash, bronchoalveolar lavage fluid, and fecal extracts. OVA‐stimulated splenic lymphoid cell cultures from immunized mice were assessed for interferon (IFN)‐γ, Interleukin (IL)‐4 and IL‐10. In comparison with mice immunized with only OVA, HNP‐1 and HBD2 induced significantly higher (P < 0.05) OVA‐specific serum IgG, lower, but not significant, serum IgM and significantly lower (P < 0.05) IFN‐γ. In contrast, HNP‐2 induced low OVA‐specific serum IgG and higher, but not significant, serum IgM. HBD1 induced significantly higher (P < 0.05) OVA‐specific serum IgG, higher, but not significant, serum IgM, and significantly higher (P < 0.05) IL‐10. The elevated serum IgG subclasses contained IgG1 and IgG2b.
Fusobacterium nucleatum impairs serum binding to Porphyromonas gingivalis biofilm
Authors: Choi J.‐I. , Kim U.‐S. , Kim S.‐J. , Son W.‐S. , Park H.‐R.
Published: December 2004

Mouse immune sera obtained by immunization with Fusobacterium nucleatum and then Porphyromonas gingivalis demonstrated an impaired binding capacity to P. gingivalis‐biofilm and lower avidity to P. gingivalis when compared with sera obtained from mice immunized with P. gingivalis alone.
Cytomegalovirus and Epstein–Barr virus DNA transcription in endodontic symptomatic lesions
Authors: Sabeti M. , Valles Y. , Nowzari H. , Simon J. H. , Kermani‐Arab V. , Slots J.
Published: December 2004

Objectives:  Productive Herpesviridae infections are implicated in the etio‐pathogenesis of aggressive periodontitis. However, virtually nothing is known about a possible role of herpesviruses in pulpal and periapical pathosis. This study employed a cDNA analysis to determine transcription of human cytomegalovirus (HCMV), Epstein–Barr virus (EBV) and herpes simplex virus (HSV) in 14 recalcitrant periapical lesions and in 2 periapical healthy control sites.

Methods:  Periapical samples were collected in conjunction with periapical surgery and kept frozen until virologic examination. RNA was isolated from periapical tissue by using a guanidinium isothiocyanate‐acid phenol procedure (TRIZOL LS Reagent, GIBCO BRL, Rockville, MD). cDNAs were amplified by means of oligonucleotides targeting highly conserved regions of the test viruses and the RT‐PCR‐100 amplification kit (Sigma–Aldrich, St Louis, MO). Standardization of PCR primer sensitivity and validation was carried out according to established methods. Amplification products were identified by agarose gel electrophoresis.

Results:  HCMV transcript was detected in 12 of 13 symptomatic and in 1 asymptomatic periapical lesion. EBV transcript was demonstrated in 8 of the 13 symptomatic lesions but not in the asymptomatic periapical lesion. HCMV and EBV dual transcription occurred at higher frequency in periapical lesions showing radiographic bone destruction of 5 mm × 7 mm or larger than in smaller size lesions (P = 0.03; Chi‐squared test). No HCMV or EBV transcription was identified in the 2 healthy control sites. HSV transcript was not detected in any study site.

Conclusion:  The present data suggest that HCMV or EBV infections participate in the pathogenesis of periapical symptomatic lesions. Herpesviruses may produce periapical pathosis as a direct result of viral infection and replication, or as a consequence of virally induced impairment of the host defense and subsequent increased virulence of resident bacterial pathogens.
Characterization and expression of adjacent proline iminopeptidase and aspartase genes from Eikenella corrodens
Authors: Selby T. , Allaker R. P. , Dymock D.
Published: December 2004

Two adjacent genes involved in nitrogen metabolism from Eikenella corrodens, with a potential role in pathogenesis, were studied. Proline iminopeptidase (Pip) activity, which may be essential for energy production and protection against host immune mechanisms, is exhibited by E. corrodens. Analysis of Pip‐expressing clones revealed an ORF of 939 bases with a predicted amino acid sequence identity of 67% to the Pip of Neisseria gonorrhoea. 200 bp downstream from pip, an ORF of 1395 bases, encoding a protein with 87% identity to a putative aspartase from the Neisseria meningitidis genome sequence, was identified. Enzymatic function was confirmed with a complemented Escherichia coli aspartase deficient mutant. The E. corrodens aspartase was found to be 77% identical to the Haemophilus influenzae aspartase sequence, which was originally identified on the basis of its ability to bind plasminogen. However, the E. corrodens aspartase had no such activity. Southern hybridization indicated both genes to be single copy and conserved within the genomes of a diverse panel of E. corrodens isolates from health and disease.
Xylitol inhibition of anaerobic acid production by Streptococcus mutans at various pH levels
Authors: Miyasawa H. , Iwami Y. , Mayanagi H. , Takahashi N.
Published: December 2004

Xylitol inhibits the glycolysis and growth of Streptococcus mutans. We studied the inhibitory effect of xylitol on the acid production of S. mutans at several pH levels under the strictly anaerobic conditions found in the deep layer of dental plaque. Xylitol inhibited the rate of acid production from glucose and changed the profile of acidic end products to formate–acetate dominance, with a decrease in the intracellular level of fructose 1,6‐bisphosphate and an intracellular accumulation of xylitol 5‐phosphate (X5P). These results were notable at pH 5.5–7.0, but were not evident at pH 5.0. Since the activity of phosphoenolpyruvate phosphotransferase for xylitol was greater at higher pH, it is suggested that xylitol could be incorporated more efficiently at higher pH and that the resultant accumulation of X5P could inhibit the glycolysis of S. mutans more effectively.
In vitro environmental regulation of Porphyromonas gingivalis growth and virulence
Authors: Kesavalu L. , Holt S. C. , Ebersole J. L.
Published: December 2004

Porphyromonas gingivalis appears to be a major contributor to periodontal disease, especially soft tissue destruction, which is reflected by the ability to cause invasive, spreading lesions, and tissue inflammation in a murine abscess model. This study investigated the role of hemin on the regulation of growth and virulence of P. gingivalis strains. P. gingivalis strains W50, A7A1‐28, 3079, 381, W50/BEI, and NG4B19 were grown in broth and on blood agar plates. P. gingivalis cells grown under iron‐depleted conditions for multiple passages showed significantly decreased lesion size in mice, in contrast to cells grown under iron‐normal (5 μg/ml) and iron‐elevated conditions. Statistically significant (P < 0.01) decreases in gingipain enzyme activity were found among the strains grown under iron‐depleted conditions. P. gingivalis grown in the presence of blood induced significantly different lesion type, lesion size, lesion onset, and mortality. Elevated hemin resulted in increased cell‐associated iron in P. gingivalis, which increased the capacity of the microorganism to survive at times of iron deprivation. These results indicate that hemin or iron availability regulates multiple aspects related to P. gingivalis virulence, including growth, survival, gingipain levels, and iron accumulation.
Starvation survival, growth and recovery of Enterococcus faecalis in human serum
Authors: Figdor D. , Davies J. K. , Sundqvist G.
Published: December 2004

The ability of Enterococcus faecalis to survive starvation for long periods in the obturated root canal is likely to be an important factor in the pathogenesis and maintenance of a persistent infection after endodontic treatment. The response of E. faecalis to starvation survival in water and glucose‐, phosphate‐ or amino acid‐limited chemically defined medium was studied, along with the capacity for growth and recovery of starved cells of E. faecalis in pooled human serum. After an initial rapid fall in cell numbers, a small remaining population of E. faecalis was able to survive in water for over 4 months and in nutrient‐limited media for extended periods. A high cell density at the onset of starvation was critical for the ability of E. faecalis to endure prolonged nutrient limitation. Upon starvation, a static population of starved cells developed and were apparently in a minimal metabolic state, since blocking cell wall synthesis with penicillin G or inhibiting DNA synthesis with norfloxacin during starvation resulted in limited change in the rate of loss of viable cells. In 50% serum, E. faecalis grew, then stabilized at a relatively constant population of 106 colony‐forming units/ml for 4 months, irrespective of the initial cell density. In summary, E. faecalis is capable of withstanding prolonged periods of starvation in a minimal metabolic state provided that there is a high cell density at the onset of starvation. Starved cells were capable of recovery upon addition of human serum.
Application and efficacy of the multi‐dose powder inhaler, EasyhalerÂ®, in children with asthma
Authors: MalmstrÃ¶m K. , Sorva R. , Silvasti M.
Published: December 2004

With powder inhalers, optimal performance is dependent on the inspiratory flow produced by the patient through the devices. The objective of this open, non‐randomized study was to evaluate the suitability of a new, multi‐dose, dry powder inhaler, the EasyhalerÂ®, for children with asthma. The peak inspiratory flow (PIF) through the Easyhaler (PIFEH) was measured with a pneumotachograph in 120 asthmatic children aged 4–16 yr. The bronchodilatory effect of 0.2 mg salbutamol through the Easyhaler was compared with that of 0.2 mg salbutamol through a metered dose inhaler (MDI) with a spacer, in 15 children with obstruction. The mean PIFEH was 56 l/min (range 22–83 l/min). The PIFEH correlated significantly with age, height, and absolute peak expiratory flow (PEF), but not with the level of obstruction (PEF percentage of predicted, range 45–146%). Only four children (aged 5, 6, 10, and 16 yr) had PIFEH values below 28 l/min, which has been shown in in vitro studies to be the threshold for effective use of the Easyhaler. In 15 children with PEF, < 85% of predicted bronchodilatory effects of 0.2 mg salbutamol through the Easyhaler and from an MDI‐cum‐spacer were equal. Most children aged 6–16 yr produce PIF values sufficient for the use of the Easyhaler. The gain of 0.2 mg salbutamol from the Easyhaler was equal to that from a new, unprimed, MDI with a spacer in children with asthma.
Food hypersensitivity in children: Clinical aspects and distribution of allergens
Authors: Rancé F. , Kanny G. , Dutau G. , Moneret‐Vautrin D. ‐A.
Published: December 2004

The aims of this work were to investigate, in children and adolescents, the clinical aspects of food hypersensitivity and the distribution of allergens, in a prospective and descriptive study. Five hundred and forty‐four pediatric cases from a series of 703 patients with food allergies, confirmed by food challenge, were studied. Their clinical characteristics and the distribution according to allergen were investigated. There was a family history of atopic disease in 70.5% of patients. Atopic dermatitis was the main symptom (275/544; 50.5% of patients), followed by urticaria and angio‐edema (165/544; 30%). There was asthma in 8.6% of patients (47 children) and anaphylaxis in 4.5% (27 patients). The rarest signs were rhinitis (n=2; 0.3%), oral allergy syndrome (n=8; 1.4%), and gastrointestinal signs (n=11; 2%). Five allergens accounted for 78% of food hypersensitivity. These allergens were: eggs (36%), peanuts (24%), cow’s milk (8%), mustard (6%), and cod (4%). Peanut was the most common allergen for children over the age of 3 yr. In this selected population, sensitivity of individuals to more than three foods was unusual (5%). Atopic dermatitis was the main symptom of food allergy in children. The symptoms changed over time, with respiratory disorders, oral allergy syndrome and ocular problems occuring later. Anaphylaxis also occured mostly in older children. Five allergens were responsible for more than three‐quarters of food allergies in children. However, the number of allergens implicated was higher for the group of children over the age of 6 yr than for younger children.
Calcification of the interclinoid and petroclinoid ligaments of sella turcica: a radiographic study of the prevalence
Authors: Cederberg R.A. , Benson B.W. , Nunn M. , English J.D.
Published: December 2004

Structured Abstract

Authors – Cederberg RA, Benson BW, Nunn M, English JD

Objectives – The purpose of this study was to evaluate the prevalence of calcifications of the sella turcica, in particular, calcification of the interclinoid and petroclinoid ligaments (PCL).

Design – Radiographic analysis of preoperative cephalometric film images.

Setting and Sample Population – Lateral cephlometric radiographs of 255 subjects presenting for orthodontic evaluation were reviewed. The number of subjects selected for this study was determined by power analysis.

Experimental Variable – Two calibrated raters reviewed cephalometric projections and scored the films using a standardized rating scale.

Outcome Measure – The rating scale classified interclinoid ligaments (ICL) into one of four categories depending on the degree of calcification and PCLs as either, no calcification, partial or complete calcification.

Results – Of all subjects, calcification of the ICL ranged from 39% rated as more than half calcified to 8% completely calcified. Petroclinoid analysis revealed 67% with no calcification, 23% with partial calcification and 9% completely calcified. Spearman's correlations were computed between age and the degree of calcification and between the degree of calcification for these two ligaments with a significant association between age and degree of calcification in the PCL, r = 0.185 (p = 0.003) and a significant association between the degree of calcification in the petroclinoid and ICLs, r = 0.186 (p = 0.003). In addition, chi‐squared tests demonstrated statistically significant associations between the presence of calcification in the PCL to the distribution of age (p = 0.041) and between the presence of calcification in the ICL to the distribution of age (p = 0.045).

Conclusion – As calcification of these ligaments has suggestive associations with disease entities, their recognition as a variant of normal anatomy should be evaluated when assessing cephalometric radiographs.
Identification of Risk for High Hospital Use: Cost Comparisons of Four Strategies and Performance Across Subgroups
Authors: Reuben David B. , Keeler Emmett , Seeman Teresa E. , Sewall Ase , Hirsch Susan H. , Guralnik Jack M.
Published: December 2004

OBJECTIVES: To determine the relative costs of four risk‐identification strategies and compare their performance in predicting hospital use by different subgroups of older persons based on age, sex, and prior hospital use.

DESIGN: Prospective validation study and cost‐comparison analysis.

SETTING: Community‐based.

PARTICIPANTS: Five thousand one hundred thirty‐eight participants of the sixth wave of three sites of the Established Populations for Epidemiologic Studies of the Elderly.

MEASUREMENTS: Four strategies (prior hospitalization data only, a 10‐item self‐report screen alone, self‐report combined with two laboratory tests, and sequential self‐report plus as‐needed use of laboratory tests when the self‐report screen is inconclusive) and 3‐year Medicare Part A hospital cost data.

RESULTS: Assuming that interventions based on screening would yield a total benefit of $1,000 per true‐positive case and a cost of $400 for each false‐positive case, the sequential strategy was slightly less expensive than the self‐report only strategy; both were considerably less expensive than the combined or hospitalization‐only strategies. Accuracy as measured by the area under the receiver operating characteristic curve for the sequential strategy was comparable for all subgroups (between 0.62 and 0.70) but was least accurate for those who had high prior use and for those aged 85 and older.

CONCLUSION: A sequential screening strategy that administers laboratory tests selectively is slightly less expensive than one that uses only self‐report items. This strategy is also accurate in both sexes, in those with various degrees of prior use, and in the oldest old.