bluuebunny/crossref_metadata_2025 huggingface dataset:
Convective activity in the Labrador Sea: Preconditioning associated with decadal variability in subsurface ocean stratification
Authors: Mizoguchi Ken‐ichi , Morey Steven L. , Zavala‐Hidalgo Jorge , Suginohara Nobuo , Häkkinen Sirpa , O'Brien James J.
Published: October 2003

The decadal variability of the convective activity in the Labrador Sea is investigated using 43 years of model output from a prognostic coupled ice‐ocean model that simulates both the Arctic and the North Atlantic Oceans. The fields of the surface density and the mixed‐layer depth indicate that the center of the convective activity is located in western Labrador Sea. The decadal variations of the convective depth are controlled to large extent by the oceanic preconditioning associated with changes in subsurface stratification. The intensity of the convective mixing varies from year to year, depending upon how strong the isopycnal doming is at the preconditioning stage at the center of the convective region. The variations of the subsurface stratification seem to be related to the subsurface temperature changes.
Detection of subsurface ice and water deposits on Mars with a mutual impedance probe
Authors: Trautner Roland , Grard Réjean , Hamelin Michel
Published: October 2003

A mutual impedance probe, also called quadrupolar probe or permittivitymeter, measures the complex permittivity of materials with a spatial resolution comparable to the average separation between its four sensors. This instrument is ideally suited for the detection of subsurface water deposits at shallow depths on Mars, since water mixtures are generally characterized by relatively large dielectric constant and conductivity. Permittivitymeters have been developed for commercial and space applications. An instrument identical to that which will land on Titan in 2004 has been tested with success in the field, and the results obtained on humid sand and in dry snow are presented. The possible applications of mutual impedance probes to the localization of water on Mars are discussed.
Continual geological activity in Athabasca Valles, Mars
Authors: Werner S. C. , van Gasselt S. , Neukum G.
Published: October 2003

Comprehensive studies of the stratigraphic relationships in the Athabasca Valles region have been performed on imagery from the Viking Orbiters and the Mars Orbiter Camera (narrow and wide angle) on board Mars Global Surveyor as well as by making use of topographic data derived from the Mars Global Surveyor Laser Altimeter (MOLA) instrument. From superimposed crater frequencies we have derived absolute surface ages by applying the Hartmann and Neukum [2001] cratering chronology model. The main channel has been incised into the Cerberus volcanic plains with an average plains age of 3.4 Ga. The main fluvial or glacial erosion processes ended 2.6 Ga ago. This result shows that the age of the valley system itself is older than commonly believed. One major possible fluvial event occurred in the topographically lower volcanic plains southwest of the valley 1.6 Ga ago. The valley itself was covered by lava episodically and ending 0.9 Ga and in case of a few younger episodes 30 Ma ago. The surface texture south of the valley system suggests a younger, possibly fluvial overprinting of the volcanic texture 30 Ma ago. The latest volcanic activity is dated to about 3 Ma ago. With the latter ages we have been able not only to confirm earlier age estimates by Berman and Hartmann [2002] but also to show that the valley system itself has undergone over a period of two billion years active geological cycles which were dominated by volcanic processes at the end.
Rock size‐frequency distributions on Mars and implications for Mars Exploration Rover landing safety and operations
Authors: Golombek M. P. , Haldemann A. F. C. , Forsberg‐Taylor N. K. , DiMaggio E. N. , Schroeder R. D. , Jakosky B. M. , Mellon M. T. , Matijevic J. R.
Published: October 2003

The cumulative fractional area covered by rocks versus diameter measured at the Pathfinder site was predicted by a rock distribution model that follows simple exponential functions that approach the total measured rock abundance (19%), with a steep decrease in rocks with increasing diameter. The distribution of rocks >1.5 m diameter visible in rare boulder fields also follows this steep decrease with increasing diameter. The effective thermal inertia of rock populations calculated from a simple empirical model of the effective inertia of rocks versus diameter shows that most natural rock populations have cumulative effective thermal inertias of 1700–2100 J m−2 s−0.5 K−1 and are consistent with the model rock distributions applied to total rock abundance estimates. The Mars Exploration Rover (MER) airbags have been successfully tested against extreme rock distributions with a higher percentage of potentially hazardous triangular buried rocks than observed at the Pathfinder and Viking landing sites. The probability of the lander impacting a >1 m diameter rock in the first 2 bounces is <3% and <5% for the Meridiani and Gusev landing sites, respectively, and is <0.14% and <0.03% for rocks >1.5 m and >2 m diameter, respectively. Finally, the model rock size‐frequency distributions indicate that rocks >0.1 m and >0.3 m in diameter, large enough to place contact sensor instruments against and abrade, respectively, should be plentiful within a single sol's drive at the Meridiani and Gusev landing sites.
Numerical models of the inversion of half‐graben basins
Authors: Buiter Susanne J. H. , Adrian Pfiffner O.
Published: October 2003

We investigate the dynamic evolution of fold and thrust structures which form by compression and inversion of a sequence of half‐graben basins. The choice for a half‐graben geometry is motivated by seismic studies and reconstructions of preinversion geometry of inverted regions, which show that rifting often leads to a series of half‐grabens. To examine the deformational structures which result from basin inversion, we use a two‐dimensional, viscous‐plastic numerical model and start our experiments from a preexisting extensional geometry. We find that synrift and postrift sediments are uplifted in the initial stages of basin inversion. This uplift is accompanied by rotation of the basement blocks beneath the basins. In the postrift sequence new shear zones form which are a continuation of basin‐bounding faults. With continuing shortening, further inversion is more difficult owing to relative strengthening of the half‐graben region. Significant surface erosion facilitates inversion. Back thrusts mainly develop in association with listric basin‐bounding faults and less for planar (domino array) faults. Weak sediments (such as salt or shales) at the base of the basins promote the development of basement shortcut faults. The presence of a postrift decollement layer tends to decouple deformation of the postrift sediments from the material below it. In our model, preexisting weak basin‐bounding shear zones are a requirement for substantial amounts of basin inversion to occur. Our numerical model results display many first order characteristics of examples from nature and analogue studies.
Dewatering and the hydraulic properties of soft, sulfidic, coastal clay soils
Authors: White Ian , Smiles David E. , Santomartino Silvana , van Oploo Pam , Macdonald Bennett C. T. , Waite T. David
Published: October 2003

Dewatering and consolidation of saturated swelling soils are governed by pressure‐dependent soil hydraulic properties. Existing measurement techniques are difficult and slow. We illustrate a simple, rapid desorption technique, developed for industrial slurries, to measure hydraulic properties of a gel‐like sulfidic, estuarine soil (∼70% water content). Measured hydraulic conductivities, K(ψ), were very small, ∼10−10 m/s, giving a representative capillary fringe thickness of ∼7 m and characteristic gravity drainage times around 40 years. Capillarity therefore dominates flow in these soils. Estimated times for dewatering this soil under surface loading with closely spaced, vertical wick drains, are 2 to 70 years, consistent with experience. A Netherlands marine clay soil, saturated with seawater, is unexpectedly wetter than the brackish estuarine soil here at the same matric potential, ψ. However, K(ψ) for both soils overlap, suggesting the engineering approximation, K(ψ) ∝ ∣ψ∣−1, for marine‐deposited clays. The functional dependencies of hydraulic properties surprisingly are not consistent with similar‐media or double‐layer theories.
Melting of small Arctic ice caps observed from ERS scatterometer time series
Authors: Smith Laurence C. , Sheng Yongwei , Forster Richard R. , Steffen Konrad , Frey Karen E. , Alsdorf Douglas E.
Published: October 2003

Time series of active microwave backscatter data from the ERS Wind Scatterometers are used to demonstrate (1) the timing of melt onset can be observed over small ice caps, as well as the major ice sheets and multi‐year sea ice; and (2) temporally integrated backscatter reduction (R) is strongly correlated with total annual positive‐degree‐days (PDD), as measured at four automated weather stations on the surface of the Greenland Ice Sheet. The latter is particularly interesting because unlike melt onset, R is a measure of melt processes integrated over an entire ablation season. Both methods work owing to the well‐known sharp decrease in radar backscatter triggered by the appearance of liquid water in a glacier snowpack. Melt onset and R are determined for 14 small Arctic ice caps from 1992–2000. Interannual and regional variability in the timing of melt onset are comparable, averaging 33 ± 9 and 38 ± 13 days, respectively. Regional variability in R exceeds interannual variability, averaging 906 ± 164 and 309 ± 130 dB·d, respectively. The brevity of the derived nine‐year records limits their statistical testing for trend. However, their qualitative interpretation suggests that the timing of melt onset is more variable for Arctic ice caps than for sea ice, and the intensity of summer surface melting increased by about 20% in the 1990s.
High aerosol optical depth biomass burning events: A comparison of optical properties for different source regions
Authors: Eck T. F. , Holben B. N. , Reid J. S. , O'Neill N. T. , Schafer J. S. , Dubovik O. , Smirnov A. , Yamasoe M. A. , Artaxo P.
Published: October 2003

The optical properties of aerosols such as smoke from biomass burning vary due to aging processes and these particles reach larger sizes at high concentrations. We compare the spectra of aerosol optical depth (τa), column‐integrated volume size distributions, refractive indices, and single scattering albedo retrieved from AERONET observations for four selected events of very high smoke optical depth (τa ∼ 2 at 500 nm). Two case studies are from tropical biomass burning regions (Brazil and Zambia) and two are cases of boreal forest and peat fire smoke transported long distances to sites in the US and Moldova. Smoke properties for these extreme events can be significantly different from those reported in more typical plumes. In particular, large differences in smoke fine mode particle radius (∼0.17 to 0.25 μm) and single scattering albedo (∼0.88 to 0.99 at 440 nm) were observed as a result of differences in fuels burned, combustion phase, and aging.
An empirical formula relating the geomagnetic storm's intensity to the interplanetary parameters: − and Δt
Authors: Wang Yuming , Shen C. L. , Wang S. , Ye P. Z.
Published: October 2003

We statistically study 105 geomagnetic storms with a Dst peak value ≤ −50 nT during 1998–2001 to examine the influence of the interplanetary parameters − and its duration Δt on the intensity of geomagnetic storms. About 33% of the events are associated with intense storms with Dstmin ≤ −100 nT. It is found that − is much more important than Δt for the formation of geomagnetic storms. A stronger − can produce a more intense storm, whereas a longer Δt can not. A simple empirical formula relating the Dst peak value to − and Δt is obtained, which shows a good correlation (CC = 0.9528) between the estimate value and the observations. This formula suggests that a compressed Bs field tends to have a more prominent geoeffectiveness. Moreover, we also identify 33 large − intervals with − > 5 mV/m and Δt > 3 hours in the same study interval, and find that they all caused intense storms (Dstmin ≤ −100 nT) and 8/9 of the great storms (Dstmin ≤ −200 nT) were due to interplanetary compressed structures.
Cenozoic evolution of Neotethys and implications for the causes of plate motions
Authors: McQuarrie N. , Stock J. M. , Verdel C. , Wernicke B. P.
Published: October 2003

Africa‐North America‐Eurasia plate circuit rotations, combined with Red Sea rotations and new estimates of crustal shortening in Iran define the Cenozoic history of the Neotethyan ocean between Arabia and Eurasia. The new constraints indicate that Arabia‐Eurasia convergence has been fairly constant at 2 to 3 cm/yr since 56 Ma with slowing of Africa‐Eurasia motion to <1 cm/yr near 25 Ma, coeval with the opening of the Red Sea. Ocean closure occurred no later than 10 Ma, and could have occurred prior to this time only if a large amount of continental lithosphere was subducted, suggesting that slowing of Africa significantly predated the Arabia‐Eurasia collision. These kinematics imply that Africa's disconnection with the negative buoyancy of the downgoing slab of lithosphere beneath southern Eurasia slowed its motion. The slow, steady rate of northward subduction since 56 Ma contrasts with strongly variable rates of magma production in the Urumieh‐Dokhtar arc, implying magma production rate in continental arcs is not linked to subduction rate.
A CHAMP‐only gravity field model from kinematic orbits using the energy integral
Authors: Gerlach Ch. , Földvary L. , Švehla D. , Gruber Th. , Wermuth M. , Sneeuw N. , Frommknecht B. , Oberndorfer H. , Peters Th. , Rothacher M. , Rummel R. , Steigenberger P.
Published: October 2003

In this paper we present results of a global gravity field recovery using half a year of CHAMP data. We use the energy integral of the motion of a satellite to transform satellite velocities into values of gravitational potential. The feasibility of this approach has already been demonstrated by several groups, using CHAMP reduced‐dynamic orbits. We show, that the potential recovered from this kind of orbits depends on the a priori gravity field used for orbit determination. Thus, it cannot be excluded that errors present in the prior field propagate into the new CHAMP gravity model. It is the intention of this paper to avoid this dependency through the use of kinematic orbits, which are free from prior information. The derived potential model, TUM‐1S, is validated by comparison to ground data and by satellite orbit residuals. It is shown to be comparable in quality to other state‐of‐the‐art gravity field models.
Determining the tropopause height from gridded data
Authors: Reichler Thomas , Dameris Martin , Sausen Robert
Published: October 2003

A method is presented to determine tropopause height from gridded temperature data with coarse vertical resolution. The algorithm uses a thermal definition of the tropopause, which is based on the concept of a “threshold lapse‐rate”. Interpolation is performed to identify the pressure at which this threshold is reached and maintained for a prescribed vertical distance. The method is verified by comparing the heights calculated from analyses of the European Centre for Medium‐Range Weather Forecasts (ECMWF) with the observed heights at individual radiosonde stations. RMS errors in the calculated tropopause heights are generally small. They range from 30–40 hPa in the extratropics to 10–20 hPa in the tropics. The largest deviations occur in the subtropics, where the tropopause has strong meridional gradients that are not adequately resolved by the input data.
Dynamical nonlinearity in the atmospheric response to Atlantic sea surface temperature anomalies
Authors: Robinson Walter A. , Li Shuanglin , Peng Shiling
Published: October 2003

Large ensembles (100 members) of atmospheric general circulation model experiments are forced throughout the Northern Hemisphere cold season by four different sea surface temperature (SST) fields: the observed climatology, the so‐called SST tripole pattern, and its tropical and its extratropical subcomponents. Late winter responses to these anomalies are of modest amplitude, in comparison with the amplitudes of climatological stationary waves, but are, because of the large ensemble, significant. Despite their modest amplitudes, the responses display additive nonlinearity, in that the sum of the separate responses to the component anomalies differs significantly from the response to the tripole. Neither the heating field nor the basin averaged zonal winds display this nonlinearity. It is most evident in a sub‐basin scale wave train, and most significant in its impact on the amplitude of the geopotential response. These results indicate that even for modest forcing, responses to patterns of SST anomalies cannot necessarily be understood as the sums of responses to constituent anomalies.
Rupture process of the 1944 Tonankai earthquake (Ms 8.1) from the inversion of teleseismic and regional seismograms
Authors: Ichinose Gene A. , Thio Hong Kie , Somerville Paul G. , Sato Toshiaki , Ishii Toru
Published: October 2003

We digitized teleseismic and regional records of the 1944 Tonankai earthquake. We used the multiple time window method to invert these records for the spatial and temporal distribution of slip and rake. We assume a 220 × 140 km fault with a spacing of 20 × 20 km and a maximum rupture velocity of 2.5 km/s. The inversion resolved an asperity along the accretionary wedge and under the Shima and Atsumi Peninsulas. The rupture propagated from southwest to northeast, and there was little slip near the hypocenter, consistent with the absence of uplift in the overlying submarine forearc basin. The peak slip is 2.3 m, and the total seismic moment is 2.4 × 1028 dyn cm (Mw 8.2). We compared the predicted and observed vertical geodetic displacements and inferred that the limit of rupture is consistent with the change from subsidence to uplift west of the Atsumi Peninsula. This suggested that the earthquake did not rupture the plate interface in the Tokai gap. We modeled the tsunami using sea‐bottom displacements generated from this slip model. The tide gauge amplitudes and frequency content are consistent with those predicted. Resolution tests from inverting synthetic seismograms computed using a simplified slip model indicated that the combination of teleseismic and regional data sets best recovers the asperity locations and peak slips given similar station geometry and degrees of freedom. An inversion of the synthetic regional data set indicates that slip artifacts can occur early in the rupture process due to many clipped records while the inversion of synthetic teleseismic data set had less resolution and recovered only 50% of the peak slip.
Deep crustal structure of Bransfield Strait: Initiation of a back arc basin by rift reactivation and propagation
Authors: Christeson Gail L. , Barker Daniel H. N. , Austin James A. , Dalziel Ian W. D.
Published: October 2003

We present the results of a wide‐angle seismic survey, consisting of a grid of five strike and three dip profiles, conducted in Bransfield Strait, Antarctica. We used a combination of two‐dimensional seismic tomography and ray tracing to constrain velocity structure in the region. Thinnest crust is located within the interpreted neovolcanic zone, but the crustal thickness of 10–15 km indicates that rifting has not progressed to the formation of normal oceanic crust. Crust thickens to 20–26 km along the South Shetland Islands pedestal and to 14–20 km along the Antarctic Peninsula margin. Along‐strike, crust generally thickens from the NE to the SW. In the across‐strike direction, crustal thinning is observed over a broader area in the NE than in the SW. The observed crustal thickness pattern is consistent with propagation of extension from the NE toward the SW. Upper mantle velocities of 7.45 ± 0.2 km/s indicate either the presence of a small amount of partial melt or normal upper mantle anisotropy with the slow direction parallel to the rift axis. Large lateral changes in upper crustal velocities along the Antarctic Peninsula margin correspond with seismically imaged structural boundaries. There is no correlation between these structural boundaries and large velocity changes or morphologic steps observed within the present‐day neovolcanic zone. We suggest that the rift topography now characterizing the Antarctic Peninsula margin formed prior to the formation of the modern basin.
Reversing circulation patterns in a tropical estuary
Authors: Valle‐Levinson Arnoldo , Bosley Kathryn T.
Published: October 2003

A combination of current velocity and water density measurements was used to characterize the basic patterns of water exchange in the Gulf of Fonseca, a tropical estuary on the Pacific Ocean side of Central America. The measurements were obtained during spring and neap tides in March (dry season) and June (wet season) of 2001 and consisted of profiles of current velocity and density along four transects. From mid‐March to mid‐April a time series of hourly surface current velocity maps was also obtained with a high‐frequency radar system of two antennas. The sampling transects and the radar coverage concentrated in the portion of the estuary that has open communication with the ocean. During the dry season, water exchange at the entrance to the gulf suggested an inverse estuarine circulation that was more robust, and its dynamics were closer to geostrophy during neap than during spring tides. It is likely that salinity increased toward the tributaries of the system and then decreased within those tributaries because of the persistent influence of fresh water. In contrast, during the wet season, salinity decreased into the estuary, and the circulation resembled that of a typical estuary. In this season the fortnightly modulation of exchange flows was masked by wind effects, which also played a relevant role in the dynamics. The net volume inflows measured in both seasons suggested that the residence time of the Gulf of Fonseca varies from 2 weeks to 1 month.
The seasonally varying isotopic composition of the sources of carbon monoxide at Barbados, West Indies
Authors: Mak John E. , Kra Gabriel , Sandomenico Theodore , Bergamaschi Peter
Published: October 2003

We have collected and analyzed air samples for 13CO, C18O, and CO concentration at Barbados, West Indies (13°N, 59°W), from July 1996 to May 2000. The δ13C values during the summer of 1996 and 1997 are among the lowest values reported for atmospheric CO, at less than −34‰ (Peedee belemnite‐CO2), but seasonal maxima are close to that reported at other stations. Seasonal lows for 1998 and 1999 are between −32.5‰ and −33‰, which is also lower than observations at higher‐latitude sites. Such low values are difficult to simulate by considering the well‐established CO sources alone, and may indicate a small, but very isotopically depleted, source of CO from the marine boundary layer, such as chlorine‐catalyzed destruction of CH4. We directly compare the observations at Barbados with data from middle‐latitude and high‐latitude Northern Hemisphere sites and construct a latitudinal dependence in the seasonal amplitude of both 13CO and C18O. We then investigate the source strengths of CO at this site using a three‐dimensional inverse model analysis, which has also been used to simulate the other data sets. Model simulations reproduce the seasonal variations in [CO], δ13C, and δ18O but do not predict the large amplitude of δ13C (which is due to the very depleted summertime δ13C values) or the absolute values for 18O. We also include a calculation of the relative strengths of certain sources based on the model inversion.
Hygroscopic growth of ammonium sulfate/dicarboxylic acids
Authors: Wise Matthew E. , Surratt Jason D. , Curtis Daniel B. , Shilling John E. , Tolbert Margaret A.
Published: October 2003

Recent studies have shown that tropospheric sulfate aerosols commonly contain 50% by mass organic species. The influence of these organics on the chemical and physical properties of sulfate aerosols is not fully established. We have measured the water activity of pure dicarboxylic acids and eutonic mixtures of ammonium sulfate/dicarboxylic acids at 25°C and have calculated van't Hoff factors for each individual system. We have also used the vapor pressure data to determine the hygroscopic growth curves for pure dicarboxylic acids and eutonic mixtures and provide power law fits to the data. For the systems studied we find that the presence of soluble dicarboxylic acids at the eutonic proportion depresses hygroscopic growth when compared to pure ammonium sulfate. In addition, we find that the presence of low‐solubility dicarboxylic acids at the eutonic proportion has no effect on the hygroscopic growth when compared to pure ammonium sulfate. To model the hygroscopic growth curves of the eutonic solutions, we employed the Zdanovskii, Stokes, and Robinson method. It was found that this approximation was accurate to within 17% for all the systems studied.
A hydraulic box model study of the Mediterranean response to postglacial sea‐level rise
Authors: Matthiesen Stephan , Haines Keith
Published: October 2003

This paper quantifies the role of changing sea level in affecting Mediterranean stratification using a new model of the strait‐basin system, which allows for explicit time dependence. During the last deglaciation, Fairbank's Meltwater Peak 1B leads to rapidly rising global sea levels and a freshening of the oceans and hence increasing influx of ever freshening Atlantic water into the Mediterranean basin. Owing to long residence times, the salinity of the deep and intermediate water reservoirs would have decreased more slowly, so that the basin was more stably stratified for a period, with possible implications for sapropel formation. Our model is used to estimate the size of this reservoir effect in comparison to the freshwater influx from the opening of the Black Sea at the Bosphorus. It is found that this mechanism affects the stratification to a similar degree as the Black Sea opening. Other climatic mechanisms have also affected the freshwater budget of the Mediterranean at this time, but their sizes are more difficult to quantify.
Salivary lactoferrin and low‐Mr mucin MG2 in Actinobacillus actinomycetemcomitans‐associated periodontitis
Authors: Groenink J. , Walgreen‐Weterings E. , Nazmi K. , Bolscher J. G. M. , Veerman E. C. I. , Van Winkelhoff A. J. , Nieuw Amerongen A. V.
Published: October 2003

Abstract. Concentrations and output of lactoferrin and of low‐Mr mucin MG2 were determined in saliva of subjects suffering from Actinobacillus actinomycetemcomitans‐associated periodontal disease and healthy subjects. Periodontal patients were clinically examined and a microbiological sample was taken from the deepest bleeding pockets in each quadrant. The number of viable A. actinomycetemcomitans was determined in the sampled sites of each patient. The MG2 output in the diseased subjects (13.6 μg protein/min) was decreased at least by a factor three compared to periodontal healthy subjects (44.3 μg protein/min). On the other hand, output of lactoferrin was not significantly different in healthy (9.5 μg/min) and diseased subjects (7.6 μg/min). Western analyses demonstrated a higher iron‐saturation of lactoferrin in diseased subjects in comparison with the healthy subjects. Lactoferrin degrading enzymes, probably derived from microbial sources, could be detected in saliva of the periodontally diseased subjects, but not in saliva of healthy subjects. The combination of iron‐saturation and degradation of lactoferrin suggests that anti‐microbial properties of lactoferrin are diminished in periodontitis patients. Moreover, the low concentration of mucin MG2 suggests a decline in mucin defence and consequently a higher susceptibility for oral infection. A negative correlation (r=−0.4, p<0.05) between the number of subgingival A. actinomycetemcomitans and lactoferrin in saliva suggested that low concentrations of lactoferrin favour the growth of the bacterium. These data indicate that a decline in the salivary defence system might increase the risk for oral infection by A. actinomycetemcomitans.
Gingival recession and toothbrushing in an Italian School of Dentistry: a pilot study
Authors: Checchi Luigi , Daprile Giuseppe , Gatto Maria Rosaria Antonella , Pelliccioni Gian Andrea
Published: October 2003

Abstract. The aim of this pilot study was to evaluate the prevalence of gingival recession at buccal tooth surfaces in a student population of Bologna University Dental School. A total of 55 subjects, attending the 1st and 5th year of the course were examined. The clinical examination involved assessment of plaque, calculus, width of keratinized gingiva, buccal probing depth and buccal gingival recession. Information about toothbrushing behavior was collected in an interview. The multiple regression analysis showed that level of education (p=0.002), toothbrushing technique (p=0.013) and toothbrushing frequency (p=0.016) are significant contributors to gingival recession. Notwithstanding the limits of a preliminary study, a higher prevalence of buccal recession is observed in the final year students, which have also a significantly lower % of buccal surfaces with calculus (p=0.014). In addition, it clearly appears that there is the necessity to investigate other factors connected with toothbrushing (pressure, time, toothpaste quantity) in order to provide an oral hygiene education without undesired effects.
Clinical study on the plaque‐removing ability of a new triple‐headed toothbrush
Authors: Zimmer Stefan , Didner Birgit , Roulet Jean‐François
Published: October 2003

Abstract. The aim of this study was to determine the plaque removing ability of a new toothbrush with a u‐shaped head (Superbrush) compared to a conventional manual toothbrush (Elmex) and an electric toothbrush with a rotating head (Braun Plak control). 36 healthy volunteers, aged 6–60 years, participated in this single blind cross‐over study. They were randomly assigned to 3 groups (A, B, C) with 12 participants each. To obtain a plaque‐free condition at the baseline, professional toothcleaning was performed in each participant. After instructions on how to use the toothbrushes, each group started the experiment with a different type of toothbrush. After 1 week of application, the Quigley‐Hein plaque index (QHI) and the proximal plaque index (API) were used to assess the oral hygiene status of each participant. This was followed by 1 week of recess before each group switched to the next type of toothbrush. The duration of the study was 5 weeks. All examinations were performed by 1 examiner. Compared to the 2 other brushes, the Superbrush was more effective in removing plaque (medians of QHI: 0.84 versus 1.56 (Elmex) and 1.56 (Braun); p<0.001; medians of API: 0.69 versus 0.94 (Elmex) and 0.87 (Braun); p<0.001). The study indicated that the new toothbrush may be an effective alternative to commonly used toothbrushes.
A 24‐h regrowth study to evaluate the plaque inhibitory properties of a proprietary liquid dentifrice
Authors: Claydon N. C. A. , Addy M.
Published: October 2003

Abstract. Dentifrices have typically been formulated as pastes. Recently however, a number of liquid products have become available. The chemical plaque inhibitory activity of such products has so far received little attention. The aim of this study was to determine the plaque inhibitory effect of a proprietary liquid dentifrice by comparison to a negative control (water) and a conventional fluoride toothpaste. The study design was a randomised single centre, single blind 3‐way crossover trial with the objective of validating claims of plaque inhibition for the liquid dentifrice. Volunteers were rendered plaque free then asked to brush for one minute with one of the three test products, following which they abstained from oral hygiene for the subsequent 24 h. The plaque area was recorded and then measured planimetrically. The results showed that more plaque accumulated with water and the liquid dentifrice compared with the fluoride toothpaste. Thus, there was a statistically significant difference between the fluoride toothpaste and water and between the fluoride toothpaste and the liquid dentifrice. There was no significant difference between the liquid dentifrice and water. It is concluded that in this particular model system, the liquid dentifrice provided little chemical plaque inhibitory action.
An evaluation of video instruction for an electric toothbrush
Authors: Addy M. , Renton‐Harper P. , Warren P. , Newcombe R. G.
Published: October 2003

Abstract. Instructions on the use of electric toothbrushes are usually derived from the written and/or diagrammatic leaflets provided with the device or perhaps less often instruction from a professional. Videos are now widely used for information transfer and the direction of physical activities. The aim of this study was to determine whether video instruction in the use of an electric toothbrush could promote efficient use of the device. The 2‐min video demonstrated the use of an oscillating, rotating electric toothbrush used by a hygienist for 15 s in each buccal and lingual quadrant. A voice‐over directed the observer to follow the hygienist's movements. The study was planned as a 2‐phase, single‐examiner blind, randomised, cross‐over study accepting there would be confounding of the 2nd period by carry‐over from the 1st. A group of 24 healthy volunteers participated who had average oral hygiene and never used an electric toothbrush. 12 subjects received the video first (VN) and 12 subjects the instructional leaflet with the device (NV). Single brushings were performed after suspending tooth cleaning for 48 h. Plaque was scored before and after brushing. A 2‐week washout period was permitted before the crossover. In period 1, plaque removal with the video was overall significantly greater than with written instructions. The effects for posterior teeth were greater than anterior and comparison between groups for posterior minus anterior differences were highly significant in favour of the VN group. In period 2, the effect of period was dominant with both groups achieving greater plaque removal in period 2 than period 1. Plaque removal by group VN remained considerably greater than group NV. Despite the confounding influences of carry‐over in this particular design of study, the results support the idea that video instruction for electric toothbrushes could be a simple and efficient way of improving plaque removal by these devices. The methodology needs to be verified in a home‐use type of investigation.
Digital radiography of interproximal bone loss; validity of different filters
Authors: Eickholz Peter , Riess Thomas , Lenhard Markus , Hassfeld Stefan , Staehle Hans Jörg
Published: October 2003

Abstract. The aim of the present study was to compare linear measurements of interproximal bone loss on digitized radiographic images after application of different filters to the gold standard of intrasurgical measurements. Immediately before surgery, 50 radiographs of 50 periodontally‐diseased teeth exhibiting interproximal bone loss, were obtained by a standardized technique in 33 patients. Intrasurgically, the distances from the cementoenamel junction (CEJ) to the alveolar crest (AC) and from the CEJ to the deepest extension of the bony defect (BD) were assessed. All radiographs were digitized with a flatbed scanner (resolution: 600×1200 dpi). Using the FRIACOM‐soft‐ware, the linear distances CEJ to AC and CEJ to BD were measured at 50 interproximal lesions from the digitized but unchanged radiographic images and also after use of 7 different basic imageprocessing modes (enhancement of contrast [dynamics], inversion, high‐pass, enhancement of gray‐level differences, mean value, histogram correction, spreading of grey values) with 11‐fold magnification. Neither the measurement of the distance CEJ to AC on the unchanged images nor assessments with any of the filters revealed significant differences from the gold standard. Multivariate analysis of variance showed the respective filter (p=0.009), intrasurgical and radiographic assessments (p<0.0001), to statistically significantly, influence the difference between intrasurgical and radiographic measurements of the distance CEJ to BD. The underestimation of the intra‐surgically assessed distance CEJ to BD by radiographic measurements ranged from 0.3±2.0 to 0.8±1.9 mm. The filter “mean value” underestimated interproximal bone loss statistically significantly more than the digitized but unchanged radiograph (p=0.05). In this study, basic digital manipulations (filters) of radiographic images failed to result in statistically significantly more valid measurements of interproximal bone loss when compared to the unchanged but digitized images. All radiographic assessments on the digitized images except for use of one filter (mean value) came close to the intrasurgical gold standard.
Prevalence and serotyping of Porphyromonas gingivalis in an Indonesian population
Authors: Van Winkelhoff A. J. , Laine M. L. , Timmerman M. F. , Van der Weijden G. A. , Abbas F. , Winkel E. G. , Arief E. M. , Van der Velden U.
Published: October 2003

Abstract. In this study, the prevalence and serotype distribution of Porphyromonas gingivalis in an Indonesian population (n=158) is described. The relationship between subgingival P. gingivalis and periodontal attachment loss was investigated. The serotype distribution and periodontal parameters were studied. Serotyping was also used to study person‐to‐person transmission between siblings and between spouses. Approximately 50% of the subjects had periodontal attachment loss ≥3 mm at 1 or more recorded sites. The population was divided into 2 subgroups based on the presence or absence of P. gingivalis. No differences in plaque index, pocket depth, clinical attachment loss, bleeding upon probing, % of sites with ≥3 mm clinical attachment loss and % of sites with probing pocket depth >5 mm, were observed between both sub‐populations. All known 6 capsular serotypes were found in the study population, with the exception of the K1 type. Detection of 1 of the known P. gingivalis serotypes was not related with the amount of clinical attachment loss. In 3 out of 29 sibships with more than one member positive for P. gingivalis, an identical P. gingivalis serotype was found. None of the 15 couples in the study shared an identical P. gingivalis serotype, indicating that transmission is probably not a common phenomenon in this population.
Substance removal on teeth with and without calculus using 308 nm XeCl excimer laser radiation
Authors: Folwaczny M. , Mehl A. , Haffner C. , Hickel R.
Published: October 2003

Abstract. It was the aim of this in vitro study to determine the potential effects of 308 nm XeCl excimer laser radiation on root surfaces when used for removing calcified deposits. The source of laser radiation was a XeCl‐excimer laser (MAX 10, Fa. Medolas, Germany) emitting ultraviolet radiation at a wavelength of 308 nm with a pulse duration of 60 ns. Subjects of irradiation were 60 extracted teeth which were devided into 2 groups of 30 samples each with (group 1) and without calculus (group 2). Specimens were irradiated with 800 laser pulses at 5 different energy‐densities per pulse of 1.0 J/cm2, 2.0 J/cm2, 3.0 J/cm2, 4.0 J/cm2 and 5.0 J/cm2. For each parameter 6 samples (n=6) were exposed to 308 nm excimer‐laser radiation. The ablation of hard tissue on the treated root surfaces was measured 3‐dimensionally with a laser scanning device (100,000 surface points per sample; accuracy: 5 μm) and evaluated with a special image analyzing software (volume, mean, median, standard deviation). In addition, a scanning electron microscopic (SEM) evaluation of the irradiated root surfaces was performed. Statistical analysis was done using ANOVA with the Scheffé‐test. The lowest amount of ablation on teeth without calculus was induced with 14.01 (±5.86) μm using laser radiation at an energy density of 2.0 J/cm2. Maximum tissue removal in this sample group was obtained with 56.67 (±21.05) μm with laser treatment at an energy density of 5.0 J/cm2. While no ablation of dental cementum was detectable after irradiating root surfaces without calculus at 1.0 J/cm2, a strong removal of calculus with a mean value of 31.91 (±4.2) μm was observed under these conditions. The results seem to indicate that a selective removal of subgingival calculus creating a homogenous shape of the root surface with 308 nm excimer laser radiation is possible. Furthermore, no signs of the formation of a smear layer nor the induction of thermal side‐effects were observed.
Severe, rapidly progressing peri‐implantitis
Authors: Fardal Ø. , Johannessen A. C. , Olsen I.
Published: October 2003

Abstract. The replacement of teeth by means of titanium implants is a safe and predictable procedure in most patients. Some studies show that a small number of patients lose the majority of their implants. Unfortunately, it is impossible to identify these patients prior to surgery. It is important to report such cases so that we may, in the future, be able to identify them before surgery. The present case showed a severe and rapid exfoliation of titanium implants. Out of 8 implants inserted in the anterior lower jaw of this patient, only two maintained osseointegration over a 2‐year period.
Presence of oxytalan fibers in human regenerated periodontal ligament
Authors: Sculean A. , Donos N. , Windisch P. , Reich E. , Gera I. , Brecx M. , Karring T.
Published: October 2003

Abstract. The aim of the present study was to investigate whether oxytalan fibers are formed in the regenerated human periodontal ligament. 6 patients, each of them exhibiting an advanced intrabony defect, were treated with a bioresorbable membrane according to the GTR‐principle. Following a healing period of 6 months, the teeth were extracted together with their surrounding soft and hard tissues and subsequently fixed in 10% buffered formalin. Following decalcification in EDTA, the specimens were embedded in paraffin and 8‐μm histological sections were cut in the mesio‐distal direction, parallel to the long axes of the teeth. The sections were stained with hematoxylin and eosin, or with the oxone‐aldehyde‐fuchsin‐Halmi staining method and examined in the light microscope. A regenerated periodontal ligament containing newly‐formed oxytalan fibers was observed in all specimens. Many of them inserted into the newly formed cementumon the root surface. It is concluded that oxytalan fibers are formed de novo in human regenerated periodontal ligament tissue.
The effect of periodontal therapy on the number of cariogenic bacteria in different intra‐oral niches
Authors: Quirynen M. , Gizani S. , Mongardini C. , Declerck D. , Vinckier F. , Van Steenberghe D.
Published: October 2003

Abstract. Several publications have reported an increased susceptibility for root caries after periodontal therapy. It has been suggested that newly exposed roots were less resistant to cariogenic species. This study examined the hypothesis that the increased susceptibility could also be related to an intra‐oral microbial shift during the initial phase of the periodontal therapy from a perio‐pathogenic to a more cariogenic flora. 10 patients with severe periodontitis were followed for 8 months after thorough scaling and root planing in combination with optimal plaque control. At baseline and after 4 and 8 months, samples were taken from the saliva, the tongue dorsum and the supragingival interdental spaces. These samples were cultured both aerobically and anaerobically in order to determine the total number of colony forming units (CFU) per sample as well as the number of CFU of Streptococcus mutans and Lactobacillus species. Oral hygiene parameters were recorded at the same visits. Finally, at baseline and at the 8 months follow‐up, changes in caries activity and periodontal health were registered. Although the total number of aerobic and anaerobic CFU in samples from the tongue and the saliva remained nearly constant over the entire observation period (variations within 0.5 log), significant (p≤0.05) increases in the number of S. mutans could be detected, especially at month 8. The significant decrease in the total number of anaerobic CFU in samples from the teeth was not associated with a reduction in the number of S. mutans, so that also for this niche the relative proportion of the latter increased. The number of lactobacilli species for the different niches showed only negligible changes (within 0.5 log values), except for samples from the teeth for which a small (1 log), but statistically significant (p<0.01), reduction could be detected. The periodontal conditions improved for all patients, but the caries activity could not be arrested. These findings seem to indicate that the increased caries susceptibility after periodontal therapy might partially be explained by a significant increase in the number of S. mutans due to ecological changes within the oral cavity. The clinical consequence of this observation would be to advocate a more strict caries preventive program during initial periodontal therapy.
Solitary sclerotic fibroma of skin: a possible link with pleomorphic fibroma with immunophenotypic expression for O13 (CD99) and CD34
Authors: Mahmood Muhammad N. , Salama Mohamed E. , Chaffins Marsha , Ormsby Adrian H. , Ma Chan K. , Linden Michael D. , Lee Min W.
Published: October 2003

Background:  Solitary sclerotic fibroma (SF) presents as a well circumscribed dermal nodule, composed of sparse spindle cells with alternating wavy collagen fibers arranged in a storiform pattern. The histogenesis and nature of this histologically distinct lesion are uncertain. Whether this peculiar tumor represents a true hamartoma or a degenerating end of various fibrous lesions such as pleomorphic fibroma (PF), dermatofibroma, or angiofibroma is still controversial. High proliferating index of spindle cells in SF argues against the possibility of being a degenerating end product of another lesion.

Methods:  We studied morphological features and immunoprofile of eight SFs, in comparison with four PFs, one collagenized dermatofibroma, two angiofibromas, and two periungual fibromas. Immunostains for CD34, CD31, O13 (CD99), Factor XIIIa, S‐100, CD68 (KP‐1), and MIB‐1 were carried out using a labeled streptavidin–biotin method with DAKO‐automated immunostainer. Paraffin blocks of two SFs were reprocessed for electron microscopic studies. Clinical data of all patients with SF were also reviewed.

Results:  Spindle cells and pleomorphic cells in SF and PF showed diffuse immunoreactivity for CD34 and O13 but were negative for CD31, S‐100, and CD68. Spindle cells in one dermatofibroma and one angiofibroma were positive for Factor XIIIa. Proliferating index (MIB‐1) was very low in all cases of SF, contradicting some previous reports.

Conclusions:  SF is a fibrotic lesion with cells positive for CD34 and O13. It shares a common immunoprofile with PF but is distinct from dermatofibroma and other common spindle cell lesions of skin. O13 expression in SF has not been previously described.