bluuebunny/crossref_metadata_2025 huggingface dataset:
Neodymium isotopic composition of Cambrian–Ordovician biogenic apatite in the Baltoscandian Basin: implications for palaeogeographical evolution and patterns of biodiversity
Authors: STURESSON ULF , POPOV LEONID E. , HOLMER LARS E. , BASSETT MICHAEL G. , FELITSYN SERGEI , BELYATSKY BORIS
Published: July 2005

Biogenic apatite preserved in 148 samples of conodonts and organophosphatic-shelled brachiopods from Cambrian through Ordovician successions of the Baltoscandian Basin (Baltica Plate) preserves a sensitive record of early Palaeozoic sea-water chemistry interpreted via neodymium isotope ratios. Consistent ${\uvarepsilon}$Nd(t) values of −9.6 to −8.3 for Lower to Middle Cambrian samples suggest no significant lateral or temporal variation across the region. Average Upper Cambrian values are −7.2 to −7.7. Sedimentary analysis suggests that the influence of continental weathering from Baltica as a major source of radiogenic Nd was negligible. Ordovician samples show a rise to −5 to −6 in the early Arenig, early–mid Llanvirn and late Caradoc. Sea-water mixing from the southeast Iapetus Ocean was a constant factor throughout Cambrian–Ordovician times. The rise reflects erosion of obducted volcanic arc complexes along the Caledonian margin, and probably also relates to pollution of the Baltica sector of Iapetus from the approaching Avalonia Plate. Patterns of evolutionary biodiversity and palaeobiogeographical linkages support the geochemical signatures in interpreting the tectonic history of the region. Extinction of lingulate brachiopod faunas in the Tremadoc, followed by subsequent recovery and emergence of benthic assemblages typical of the Ordovician Evolutionary Fauna in the Billingen–early Volkhov regional stages coincide with significant changes in geochemical characteristics of water masses across the Baltoscandian basin. The early and mid Ordovician (Arenig to Llandeilo) brachiopod faunas of the North Estonian Confacies Belt are characterized by high endemism and low turnover rates, whereas increased immigration resulted in the extinction of a number of local lineages in the late Llanvirn. From the mid Caradoc to mid Ashgill, when Baltica was drifting on a course to collide eventually with Avalonia and gradually approach Laurentia, brachiopod assemblages were characterized by higher turnover rates. At the same time they gradually became more cosmopolitan and less influenced by the invasion of new faunas.
The logic of demand in Haskell
Authors: HARRISON WILLIAM L. , KIEBURTZ RICHARD B.
Published: July 2005

Haskell is a functional programming language whose evaluation is lazy by default. However, Haskell also provides pattern matching facilities which add a modicum of eagerness to its otherwise lazy default evaluation. This mixed or “non-strict” semantics can be quite difficult to reason with. This paper introduces a programming logic, P-logic, which neatly formalizes the mixed evaluation in Haskell pattern-matching as a logic, thereby simplifying the task of specifying and verifying Haskell programs. In p-logic, aspects of demand are reflected or represented within both the predicate language and its model theory, allowing for expressive and comprehensible program verification.
Eine Interventionsstudie zum Einfluss des Human Resource Managements im betrieblichen Arbeits- und Gesundheitsschutz
Authors: Elke Gabriele , Zimolong Bernhard
Published: July 2005

Zusammenfassung. Nach einem Literaturüberblick zum Stand der Organisations- und Managementforschung für die Verbesserung von Sicherheit und Gesundheit in Organisationen wird eine Interventionsstudie in zwei Abteilungen eines Produktionsunternehmens vorgestellt. Der Interventionsschwerpunkt lag auf den Gestaltungsfeldern Human Resource Management und Systemmanagement. Sie sind Systemkomponenten des ganzheitlichen Managementsystems GAMAGS (Ganzheitliches Management des betrieblichen Arbeits- und Gesundheitsschutzes). Die Überprüfung der Interventionen erfolgte über einen Zeitraum von zwei Jahren. Die abhängigen Untersuchungsvariablen bildeten die meldepflichtigen Arbeitsunfälle, die krankheitsbedingten Fehlzeiten sowie die FAGS-Skalen (Fragebogen zum Arbeits- und Gesundheitsschutz) zur Personalführung, Sicherheitskultur und zur individuellen Risikokompetenz. Die Entwicklungen verliefen in den zwei Abteilungen sehr unterschiedlich, sowohl aus Sicht der Vorgesetzten und Mitarbeiter wie auch hinsichtlich der objektiven Ergebnisse. In einer Abteilung gab es nur eine vorübergehende Reduzierung der Unfallzahlen. In der anderen Abteilung entsprach die Entwicklung den Erwartungen. Die inferenzstatistischen Analysen der personal- und organisationspsychologischen Variablen lieferten eine hinreichende Erklärung für diese Ergebnisse. Zwei Regressionsanalysen konnten den signifikanten Einfluss der Einführung von GAMAGS auf die Entwicklung der Arbeitsunfälle und der krankheitsbedingten Fehlzeiten nachweisen.
Die Normative und Subjektive Arbeitsanalyse (NUSA)
Authors: Riedel Jeannette , Meyer Christian , Rumpf Hans-Jürgen , John Ulrich , Hapke Ulfert
Published: July 2005

Zusammenfassung. Im vorliegenden Beitrag wird die Normative und Subjektive Arbeitsanalyse (NUSA) vorgestellt, welche auf Grundlage des Karasek-Modells entwickelt wurde und die Dimensionen Arbeitsanforderungen und Handlungsspielraum sowie physikalische Arbeitsbedingungen als gesundheitsrelevante Arbeitsplatzmerkmale erfassen soll. Es werden psychometrische Eigenschaften der NUSA und Ergebnisse der Validität berichtet. Die Untersuchung ist Teil der Studie Transitions in Alcohol Consumption and Smoking (TACOS), die auf einer repräsentativen Einwohnermeldeamtstichprobe der 18- bis 64-jährigen Allgemeinbevölkerung einer norddeutschen Region basiert. Es wurden 2 547 berufstätige Personen in die Auswertung einbezogen. Als Ergebnis der Faktorenanalyse werden die Dimensionen des Karasek-Modells und die Skala der physikalischen Arbeitsbedingungen repliziert. Für alle drei Skalen wurden befriedigende Reliabilitäten und interne Konsistenzen ermittelt. Das Verfahren zeigt eine hinreichende Sensibilität bei der Differenzierung relevanter Gruppen hinsichtlich der beruflichen Stellung, des Geschlechts und der Schulbildung. Die Vor- und Nachteile sowie die Einsatzgebiete der NUSA werden diskutiert.
Toward a synthesis of equatorial spread F onset and suppression during geomagnetic storms
Authors: Martinis C. R. , Mendillo M. J. , Aarons J.
Published: July 2005

We present initial steps toward unifying our understanding of storm time equatorial spread F (ESF) by searching for the common elements in past case studies and statistical occurrence patterns. We show that the development (or inhibition) of equatorial irregularities during magnetically active periods can be understood using the AE‐parameterized Fejer‐Scherliess model for disturbance vertical drifts versus storm time and local time. This model takes into account the different sources of perturbation electric fields (magnetospheric and ionospheric dynamos) that ultimately drive the equatorial vertical drifts, showing prompt and delayed effects in the premidnight sector (where both generation and suppression can occur), as well as in the postmidnight period where generation dominates. The postsunset period exhibits the greatest variability for storm time ESF versus longitude, and thus we demonstrate the Fejer‐Scherliess model's applicability in a test case (6 April 2000) that had an AE pattern compatible with their parameterization scheme. The model successfully accounts for the pronounced longitude confinement in the observed postsunset ESF patterns. Finally, we move beyond the empirically derived relationships between geomagnetic indices and the occurrence of ESF (Aarons, 1991) into a framework of true solar‐terrestrial parameters that drive such effects. Additional case studies taken from the published literature are then used to show a consistent linkage between postsunset ESF onset and the interplanetary electric field (IEF) Esw. While AE, Dst, Kp and Dst/dt indices were used in earlier studies to determine the dusk‐longitude sector of disturbance electric fields, here we attribute to the IEF the main role in the determination of this longitude sector.
Substorm injections produce sufficient electron energization to account for MeV flux enhancements following some storms
Authors: Mithaiwala M. J. , Horton W.
Published: July 2005

One of the main questions concerning radiation belt research is the origin of very high energy (>1 MeV) electrons following many space storms. Under the hypothesis that the plasma sheet electron population is the source of these electrons, which are convected to the outer radiation belt region during substorms, we estimate the flux of particles generated at geosynchronous orbit. We use the test particle method of following guiding center electrons as they drift in the electromagnetic fields during substorm dipolarization. The dipolarization pulse model electromagnetic fields are taken from the Li et al. (1998) substorm particle injection model. We find that a substorm dipolarization can produce enough electrons within geosynchronous orbit to account for the electrons seen following storms. To do this, we compute transport ratios of plasma sheet electrons, that is, the relative ratio of plasma sheet electrons that are transported and trapped in the inner magnetosphere during substorms, as well as the change in energy of the electrons. Since high fluxes of MeV electrons are only seen following storms and not isolated substorms, it is likely that these electrons may serve as a source population for other energization mechanisms which accelerate the electrons to MeV energies. Furthermore, we do parametric studies of the dipolarization model to understand physically what conditions enable the generation of this source population.
Interstellar dust flux measurements by the Galileo dust instrument between the orbits of Venus and Mars
Authors: Altobelli N. , Kempf S. , Krüger H. , Landgraf M. , Roy M. , Grün E.
Published: July 2005

We present an analysis of the data obtained by the Galileo in situ dust instrument for interstellar dust (ISD). Between December 1989 and the end of 1993, three orbit segments were favorable for the detection of ISD at less than 3 AU heliocentric distance. After removing background events from the data sample, which were mostly due to interplanetary dust impactors, we infer that the flux of ISD grains between 0.7 AU and 3 AU is about 4 × 10−5 m−2 s−1. This result is compatible with the ISD flux of 3 × 10−5 m−2 s−1 (grain size ≈ 0.4 μm) derived from the Cassini measurements at about 1 AU. Using a new concept called “ISD β spectroscopy,” we are able to estimate at different locations in the inner solar system the ISD flux alteration resulting from the competing effects of radiation pressure and gravitation. In particular, we confirm results of previous Ulysses dust data analysis showing that radiation pressure prevents smaller ISD grains (radius smaller than ≈ 0.3 μm) from reaching the innermost region of the solar system. Furthermore, our analysis shows the relevance of gravitational focusing in the dynamics of bigger ISD grains (micron‐sized grains). The Galileo measurements were performed 10 years before the Cassini measurements. Thus the available ISD data now cover almost a full 11‐year solar cycle. Nonetheless, the flux of ISD grains with radius bigger than 0.4 μm shows no significant temporal variation. This suggests that the dynamics of these ISD grains is not influenced much by the interaction with the time‐dependent solar magnetic field.
Bulk plasma properties at geosynchronous orbit
Authors: Denton M. H. , Thomsen M. F. , Korth H. , Lynch S. , Zhang J. C. , Liemohn M. W.
Published: July 2005

We present a comprehensive study of plasma properties at geosynchronous orbit for electron and ion energies between ∼1 eV and ∼45 keV, between 1990 and 2001. The variations of temperature and density are analyzed as functions of local time, magnetospheric convection strength, and the strength of the ring current. Various parameters derived from temperature and density are calculated to elucidate the temporal and spatial location of delivery of plasma sheet material into the inner magnetosphere. We find that the electron and proton densities are greatest in the dawn region for the periods of highest convection and ring current strength. We perform a superposed epoch analysis of 283 geomagnetic storms which occurred between 1991 and 2001 and examine the temporal variation of the plasma at geosynchronous orbit as a function of storm phase. This analysis demonstrates the local time variability of delivery from the plasma sheet into the inner magnetosphere and the concurrent changes in temperature and pressure. We demonstrate that the density of electrons in the plasma sheet is strongly dependent upon the magnetospheric convection strength and, for the first time, upon solar activity. Electron density at geosynchronous orbit is strongly correlated with solar activity. The average plasma sheet electron density at solar maximum can be a factor of two or more higher than that at solar minimum. We also outline a method to estimate the composition of the plasma sheet from MPA measurements and calculate the O+ and H+ density variations with solar cycle as a function of Kp and local time. We show that the O+ and H+ plasma sheet densities increase with increasing solar activity, as does the O+/H+ density ratio. During times of high solar activity and strong convection, the O+ and H+ densities may be comparable.
Diurnal variation of ozone depletion during the October–November 2003 solar proton events
Authors: Verronen Pekka T. , Seppälä Annika , Clilverd Mark A. , Rodger Craig J. , Kyrölä Erkki , Enell Carl‐Fredrik , Ulich Thomas , Turunen Esa
Published: July 2005

We have studied the short‐term effect of the October–November 2003 series of solar proton events on the middle atmosphere. Using the proton flux measurements from the GOES–11 satellite as input, we modeled the effect of the precipitating particles between 26 October and 6 November with a one–dimensional ion and neutral chemistry model. Then we compared the results with ground‐based radio propagation measurements, as well as with NO2 and ozone profiles made by the GOMOS satellite instrument. The very low frequency signal experiences up to −7 dB absorption during the largest solar proton event, subsequently varying with time of day during the recovery phase. The model and radio propagation observations show very good agreement, suggesting that the model is capturing the impact of solar protons on the ionosphere. The model results show order‐of‐magnitude changes in odd hydrogen and odd nitrogen concentrations, as well as ozone depletion varying from 20% at 40 km altitude to more than 95% at 78 km. The magnitude and altitude distribution of ozone depletion is found to depend not only on the flux and energy of the protons but also on the diurnal cycle of atomic oxygen and ozone‐depleting constituents so that the largest depletions of ozone are seen during sunrise and sunset. The after‐event recovery of ozone is altitude‐dependent because of the differences in the recovery of odd hydrogen and odd nitrogen and also because of a relatively faster ozone production at higher altitudes. The modeled and measured NO2 profiles agree well at altitudes 35–60 km, particularly during times of large concentrations observed after the solar proton event onset. A comparison of the time series of ozone depletion shows a good agreement between the model and observations.
On radar imaging of current features: 1. Model and comparison with observations
Authors: Kudryavtsev V. , Akimov D. , Johannessen J. , Chapron B.
Published: July 2005

A new radar imaging model of ocean current features is proposed. The simulated normalized radar cross section (NRCS) takes into account scattering from “regular” surfaces (by means of resonant Bragg scattering and specular reflections) and scattering from breaking waves. The description of background wind waves and their transformation in nonuniform medium is based on solution of the wave action conservation equation. Wave breaking plays a key role in the radar imaging model. Breaking waves scatter radio waves (thus directly contributing to the NRCS), provide energy dissipation in wind waves (thus defining the wave spectrum of intermediate scale waves), and generate short surface waves (thus affecting Bragg scattering). Surface current, surfactants accumulated in the convergence zone, and varying wind field are considered as the main sources for the NRCS manifestations of current features. The latter source can result from transformation of atmospheric boundary layer over the sea surface temperature front. It is shown that modulation of wave breaking significantly influences both radar returns and short wind waves. In the range of short gravity waves related to Ku‐ X‐, and C‐bands, the modulation of Bragg waves through wave breaking is the governing mechanism. The model is tested against well‐controlled experiments including JOWIP, SARSEX, and CoastWatch‐95. A reasonably good agreement between model and observations is obtained.
Spatial distribution of heterotrophic bacteria in the northeast Atlantic (POMME study area) during spring 2001
Authors: Thyssen Melilotus , Lefèvre Dominique , Caniaux Guy , Ras Josephine , Fernández Camila I. , Denis Michel
Published: July 2005

Heterotrophic bacteria abundances, total chlorophyll a (Tchla), and nitrate concentrations were determined during the spring cruise (23 March–13 April 2001) of the Programme Océan Multidisciplinaire Méso Echelle (POMME) in the northeastern Atlantic between 39.0°–44.5°N and 16.6°–20.6°W. Sampling covered a grid of 81 stations regularly spaced. Three bacteria subpopulations (HNA1, HNA2, and LNA) were resolved by flow cytometry on the basis of their nucleic acid content, after staining with SYBR Green II (molecular probes), and by their scatter properties. The bacterial distribution was investigated down to 600 m depth. HNA2 were essentially observed in the upper 200 m and were not present at all stations. HNA1 dominated in the surface layer and were positively linked to Tchla. This relationship exhibited some heterogeneity due to the latitudinal evolution of the phytoplankton bloom and the seasonal thermocline formation already occurring in the south. In contrast, LNA dominated the bacterial subgroups below 100 m depth, and their distribution bore the fingerprint of the geostrophic current field and the mesoscale features identified in the study area, i.e., cyclonic and anticyclonic eddies and frontal structures.
On radar imaging of current features: 2. Mesoscale eddy and current front detection
Authors: Johannessen J. A. , Kudryavtsev V. , Akimov D. , Eldevik T. , Winther N. , Chapron B.
Published: July 2005

The surface signatures of meandering fronts and eddies have been regularly observed and documented in synthetic aperture radar (SAR) images. Wave‐current interactions, the suppression of short wind waves by natural film, and the varying wind field resulting from atmospheric boundary layer changes across an oceanic temperature front all contribute to the radar image manifestation of such mesoscale features. The corresponding imaging mechanisms are quantitatively explored using a new radar imaging model (Kudryavtsev et al., 2005) that solves the energy balance equation where wind forcing, viscous and wave breaking dissipation, wave‐wave interactions, and generation of short waves by breaking waves are taken into account. High‐quality and synoptic in situ observations of the surface conditions should ideally be used in this model. However, such data are rarely available. Instead, the fields of temperature and ocean current are herein derived from two distinct numerical ocean models. SAR image expressions of current fronts and eddies are then simulated based on these fields. The comparison of simulated images with European Remote Sensing (ERS) SAR and Envisat advanced SAR (ASAR) images is favorable. We consequently believe that the new radar imaging model provides promising capabilities for advancing the quantitative interpretation of current features manifested in SAR images.
Retrieval of cloud phase and crystal habit from Multiangle Imaging Spectroradiometer (MISR) and Moderate Resolution Imaging Spectroradiometer (MODIS) data
Authors: McFarlane Sally A. , Marchand Roger T. , Ackerman Thomas P.
Published: July 2005

A method of retrieving cloud phase and the dominant ice crystal habit from radiances measured by the Multiangle Imaging Spectroradiometer (MISR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) has been developed. The retrieval method takes advantage of the differences in the phase function of various particle shapes as a function of scattering angle. Three case studies are presented which illustrate the retrieval method. A comparison with semi‐coincident in situ observations for one case study indicates that the retrieved crystal habits are consistent with the observations.
Lightning‐generated NOX and its impact on tropospheric ozone production: A three‐dimensional modeling study of a Stratosphere‐Troposphere Experiment: Radiation, Aerosols and Ozone (STERAO‐A) thunderstorm
Authors: DeCaria Alex J. , Pickering Kenneth E. , Stenchikov Georgiy L. , Ott Lesley E.
Published: July 2005

A three‐dimensional cloud‐scale chemical transport model has been used to simulate trace gas transport, lightning NO production, and photochemical ozone production in the 12 July 1996 storm observed during the Stratosphere‐Troposphere Experiment: Radiation, Aerosols and Ozone (STERAO‐A) field experiment. The model is driven by meteorological fields from a nonhydrostatic cloud‐resolving model (see Stenchikov et al., 2005). An assumption that both cloud‐to‐ground and intracloud flashes produce 460 moles NO/flash on average yielded the best comparison with the profile of NO observed in the storm anvil. Scenarios in which the NO production of an intracloud flash was 75 to 100% of the production of a cloud‐to‐ground flash best matched the column NOx mass computed from observations. Additional ozone production attributable to lightning NO within the storm cloud during the lifetime of the storm was very small (∼2 ppbv). However, simulations of the photochemistry over the 24 hours following the storm show that an additional 10 ppbv of ozone production can be attributed to lightning NO production in the upper troposphere. Convective transport of HOx precursors led to the generation of a HOx plume, which substantially aided the downstream ozone production. Soluble species mixing ratios in the simulated cloud were all within a factor of two of observations.
Diatom‐bound 15N/14N: New support for enhanced nutrient consumption in the ice age subantarctic
Authors: Robinson Rebecca S. , Sigman Daniel M. , DiFiore Peter J. , Rohde Melissa M. , Mashiotta Tracy A. , Lea David W.
Published: July 2005

Diatom‐bound 15N/14N was used to reconstruct the glacial nutrient status of the Subantarctic Zone in the Southern Ocean. Down‐core records from both the Pacific and Indian sectors show δ15N of 5 to 6‰ during the Last Glacial Maximum and a decrease, coincident with the glacial termination, to values as low as 2‰. The effect of either diatom assemblage or physiological change on the diatom‐bound 15N/14N is unknown and cannot yet be ruled out as a possible explanation for the observed change. However, the consistency between Indian and Pacific sector records and with other paleoceanographic data suggests that the glacial‐interglacial difference in diatom‐bound 15N/14N was driven by higher consumption of nitrate in the subantarctic surface during the last ice age. Such a change in nutrient consumption may have resulted from atmospheric iron fertilization and/or decreased glacial mixed layer depths associated with sea ice melting. Enhanced nutrient consumption in the glacial subantarctic would have worked to lower the concentration of CO2 in the ice age atmosphere. It also would have reduced the preformed nutrient content of the low‐latitude thermocline, leading to decreases in low‐latitude productivity, suboxia, and denitrification.
A fundamental probability distribution for heavy rainfall
Authors: Wilson P. S. , Toumi R.
Published: July 2005

There is currently no physical understanding of the statistics of heavy precipitation. These statistics are, however, central to diagnosing climate change and making weather risk assessments. This work derives a fundamental rainfall distribution. Interpretation of the water balance equation gives a simple expression for precipitation as the product of mass flux or advected mass, specific humidity and precipitation efficiency. Statistical theory predicts that the tail of the distribution of the product of these three random variables will have a stretched exponential form with a shape parameter of 2/3. This is verified for a global daily precipitation data set. The stretched exponential tail explains the apparent ‘heavy’ tailed behaviour of precipitation under standard assumptions used in extreme value theory. The novel implications for climate change are that the stretched exponential shape is unlikely to change, although the scale may, and precipitation efficiency is important in understanding future changes in heavy precipitation.
Impact of air traffic on cirrus coverage
Authors: Stubenrauch Claudia J. , Schumann Ulrich
Published: July 2005

TOVS Path‐B satellite data provide information on effective high cloud amount and relative humidity for the period 1987 to 1995. Differences in trends of seasonal mean effective high cloud amount between situations favorable for contrails and for cirrus are analyzed in regions with high and low air traffic density. In regions with especially high air traffic density, a significantly stronger increase of effective high cloud amount is found for situations with sufficiently cold and humid air masses favorable for contrails than for all situations in general or for situations favorable for cirrus. Situations of potential contrails occur in about 5 to 10% of all situations, and their seasonal effective high cloud amount averages lie between about 7% and 22%. Indicators of cirrus increase due to air traffic corresponding to the difference in trends of effective high cloud amount between potential contrail situations and cirrus or all situations are about 2.8%–3.5% and 1.6%–4.7% per decade over Europe and the North Atlantic flight corridor, respectively. Weighted by frequency of potential contrail occurrence, the overall increase amounts to at least 0.20%–0.25% and 0.08%–0.24% per decade over regions with very high air traffic (Europe and the North Atlantic flight corridor, respectively).
Wind‐driven summer surface hydrography of the eastern Siberian shelf
Authors: Dmitrenko Igor , Kirillov Sergey , Eicken Hajo , Markova Natalia
Published: July 2005

High interannual variability of summer surface salinity over the Laptev and East Siberian Sea shelves derived from historical records of the 1950s–2000s is attributed to atmospheric vorticity variations. In the cyclonic regime (positive vorticity) the eastward diversion of the Laptev Sea riverine water results in a negative salinity anomaly to the east of the Lena Delta and farther to the East Siberian Sea, and a positive anomaly to the north of the Lena Delta. Anticyclonic (negative) vorticity results in negative salinity anomalies northward from the Lena Delta due to freshwater advection toward the north, and a corresponding salinity increase eastward.
Global statistics of inertial motions
Authors: Park Jong Jin , Kim Kuh , King Brian A.
Published: July 2005

Statistics of inertial currents in the North Pacific, North Atlantic, and Southern Ocean are derived for the period 1997–2003 from surface trajectories of Argo profiling floats by employing a method developed recently by Park et al. (2004). The distribution of inertial amplitudes is non‐Gaussian in the range 0∼80 cm/sec with an average value of 13.7 cm/sec. The inertial amplitude in the mid‐latitude (30°∼45°N) band exceeds those in both the low (15°∼30°N) and high (45°∼60°N) latitude bands. In three basins, the amplitude in summer is greater than that in winter by 15%∼25%. The inertial energy in the mixed layer reaches approximately 1100 J/m2∼1165 J/m2 globally. The spatiotemporal patterns of inertial amplitudes in the North Atlantic mostly depend on the MLD, which exhibits strong meridional gradients. However, the small meridional gradient of the MLD in the North Pacific does not contribute significantly to the spatial distribution of inertial amplitudes. The total inertial energy estimated from the floats is consistent with the theory that inertial energy could contribute significantly to sustaining the meridional overturning circulation.
Evidence for the Antarctic circumpolar wave in the sub‐Antarctic during the past 50 years
Authors: Mélice J.‐L. , Lutjeharms J. R. E. , Goosse H. , Fichefet T. , Reason C. J. C.
Published: July 2005

Sea surface temperatures have been measured at the islands of Marion (47°S, 38°E) from 1949 to 1998 and Gough (40°S, 10°W) from 1956 to 1998. These are some of the longest records of their kind in the sub‐Antarctic. Evidence for the passage of the Antarctic circumpolar wave is apparent at each island, presenting one of the most extended documentation of this phenomenon to date. The highest, negative correlation between the anomalies in each island's sea surface temperature record and the sea ice extent anomalies is observed directly south of each individual island. The sea surface temperature anomalies at Gough lead those at Marion by about one year in average, with mean precession periods of 8.6, 8.9, and 10.4 years in the 60s, 80s and 90s, respectively. These precession periods can be compared to those observed in the sea ice extent anomalies.
Large‐scale fluvial grade as a nonequilibrium state in linked depositional systems: Theory and experiment
Authors: Muto Tetsuji , Swenson John B.
Published: July 2005

A graded river conveys its sediment load without net aggradation or degradation. Grade is thought to represent the equilibrium state of a river system subject to steady allogenic forcing. We address the concept of grade in linked depositional systems through a combination of mathematical modeling and flume experiments. We develop a moving boundary morphodynamic model of fluviodeltaic sedimentation and use it to quantify the conditions necessary for a state of sustained grade in an alluvial‐deltaic system developing on a uniformly sloping shelf. To test our theory, we conducted a series of flume experiments in which we constructed laboratory‐scale fluviodeltaic systems under specific relative sea level histories. On large spatiotemporal scales, our theoretical and experimental results suggest an alternative view of grade as an intrinsically nonequilibrium state that requires a fall in relative sea level. Under conditions of stillstand or rise in relative sea level, the equilibrium (graded) profile does not exist, and the alluvial river will always aggrade. With a steady sediment supply, alluvial grade can be sustained if relative sea level falls with a specific, square‐root‐of‐time dependence. Common sequence‐stratigraphic conceptualizations of alluvial river response to sea level change suggest that rivers aggrade and degrade in response to relative sea level rise and fall, respectively. We show that rivers can remain aggradational if the rate of sea level fall is sufficiently small. The boundary between aggradational and degradational states is the graded state described here: that associated with a relative sea level fall that varies with the square root of time.
Multispectral x-ray imaging with a pinhole array and a flat Bragg mirror
Authors: Koch J. A. , Barbee T. W. , Izumi N. , Tommasini R. , Mancini R. C. , Welser L. A. , Marshall F. J.
Published: July 2005

We describe a multiple monochromatic x-ray imager designed for implosion experiments. This instrument uses an array of pinholes in front of a flat multilayered Bragg mirror to provide many individual quasimonochromatic x-ray pinhole images spread over a wide spectral range. We discuss design constraints and optimizations, and we discuss the specific details of the instrument we have used to obtain temperature and density maps of implosion plasmas.
Wave-turbulence interaction of a low-speed plane liquid wall-jet investigated by particle image velocimetry
Authors: Li F.-C. , Kawaguchi Y. , Segawa T. , Suga K.
Published: July 2005

The surface-wave amplitude (free-surface level) and the turbulent velocity field of the liquid phase of a plane wall-jet flow have been simultaneously measured by means of particle image velocimetry, which allows for the investigation of surface waves and wave-turbulence interaction. The Reynolds number, Weber number, and Ohnesorge number of the tested flow, based on the bulk velocity, height of the closed channel, and physical properties of water, were 3.6×104, 1.2×103, and 9.5×10−4, respectively. Based on the measured datasets of the velocity field and free-surface level, the characteristics of the wave-turbulence interaction as well as the statistics of surface waves and turbulent velocity field were studied. The characteristics of the turbulent velocity field near the wavy free surface obtained in this study were different from those obtained previously for open-channel flows with no shear at the interface or negligible deformation of the free surface. It was found that reverse vortex motion was predominant beneath the wave crest to a depth of about 2mm under the tested flow condition at the near field of the wall jet, which was conjectured to be the main feature before the onset of breakup of the free surface.
A software package to manipulate space dependencies and geometry in magnetic confinement fusion
Authors: Moret J.-M.
Published: July 2005

Improvement in the performance of magnetic confinement devices for nuclear fusion relies on the optimization of the geometry of the plasma: either the two-dimensional (2D) cross-section shape in tokamaks with toroidal symmetry or the 3D magnetic configuration in stellerators. The variation in time and space of the plasma parameters in these devices is measured using tomographic or imaging systems with a large number of detectors. To integrate the geometrical manipulations required for the analysis of experimental data, the description of the confining magnetic field configuration and the modeling and simulation of the physical processes within the plasma, an object oriented software package has been developed. Classes in this package are used to describe several coordinate systems, including magnetic flux coordinates, the geometry of the measurement systems, the configuration of the magnetic field and space, and time dependent functions representing plasma parameters. Methods applied on these classes can then easily implement coordinate system transformations, as well as interpolation of and integro-differential calculus on, space and time dependent functions. The geometrical description and characteristics of the magnetic flux surfaces have a natural representation in this environment, allowing the ready computation of the intersection of measurement viewing lines with a coordinate mesh and with flux surfaces, as well as the calculation of the corresponding transfer matrix used in tomographic inversion. The selected numerical methods used in these manipulations and their performances are also presented.
Soft-x-ray photoemission spectroscopy and ab initio studies on the adsorption of NO2 molecules on defective multiwalled carbon nanotubes
Authors: Lozzi L. , Picozzi S. , Armentano I. , Valentini L. , Kenny J. M. , La Rosa S. , Coreno M. , de Simone M. , Delley B. , Santucci S.
Published: July 2005

The adsorption of NO2 molecules on defective multiwalled carbon nanotubes has been studied by soft-x-ray photoemission. The valence band and carbon core-level spectra have been acquired before, during, and after NO2 exposure. The spectra show a reversible decrease of the density of states at the top of the valence band when NO2 molecules are adsorbed on the (carbon nanotubes) CNTs. No shift of the C 1s spectra has been observed. Theoretical calculations, using density-functional theory, have been performed on the CNT+NO2 system, considering semiconducting nanotubes with different diameters and introducing a Stone–Wales [Chem. Phys. Lett. 128, 501 (1986)] defect. The calculation confirms the decrease of the density of states at the top of the valence band in the CNT+NO2 system, while close to the adsorption site new states appear very close to the Fermi level.
The steady propagation of a surfactant-laden liquid plug in a two-dimensional channel
Authors: Fujioka Hideki , Grotberg James B.
Published: July 2005

In this study, we investigate the steady propagation of a liquid plug in a two-dimensional channel lined by a uniform, thin liquid film. The liquid contains soluble surfactant that can exist both in the bulk fluid and on the air-liquid interface. The Navier-Stokes equations with free-surface boundary conditions and the surfactant transport equations are solved using a finite volume numerical scheme. The adsorption/desorption process of the surfactant is modeled based on pulmonary surfactant properties. As the plug propagates, the front meniscus sweeps preexisting interfacial surfactant from the precursor film, and the surfactant accumulates on the front meniscus interface. As the front meniscus converges on the precursor film from the region where the interfacial surfactant concentration is maximized, the Marangoni stress opposes the flow. In this region, the Marangoni stress results in nearly zero surface velocity, which causes the precursor film thickness near the meniscus to be thicker than the leading film thickness. Since the peaks of wall pressure and wall shear stress occur due to narrowing of the film thickness, the observed increase of the minimum film thickness weakens these stresses. In the thicker film region, however, the drag forces increase due to an increase in the surfactant concentration. This causes the overall pressure drop across the plug to increase as a result of the increasing surfactant concentration. A recirculation flow forms inside the plug core and is skewed toward the rear meniscus as the Reynolds number increases. When no surfactant exists, the recirculation flow is in contact with both the front and the rear interfaces. As the surfactant concentration increases, the Marangoni stress begins to rigidify the front interface and forces the recirculation flow away from the front interface. Subsequently, the recirculation flow is directed away from the rear interface in a manner similar to that for the front interface. When the plug length is shorter, this change in recirculation pattern occurs at a smaller surfactant concentration.
The electrical double layer for a fully asymmetric electrolyte around a spherical colloid: An integral equation study
Authors: Guerrero-García G. Iván , González-Tovar Enrique , Lozada-Cassou Marcelo , de J. Guevara-Rodríguez F.
Published: July 2005

The hypernetted chain/mean spherical approximation (HNC/MSA) integral equation for a totally asymmetric primitive model electrolyte around a spherical macroparticle is obtained and solved numerically in the case of size-asymmetric systems. The ensuing radial distribution functions show a very good agreement when compared to our Monte Carlo and molecular-dynamics simulations for spherical geometry and with respect to previous anisotropic reference HNC calculations in the planar limit. We report an analysis of the potential versus charge relationship, radial distribution functions, mean electrostatic potential, and cumulative reduced charge for representative examples of 1:1 and 2:2 salts with a size-asymmetry ratio of 2. Our results are collated with those of the modified Gouy–Chapman (MGC) and unequal radius modified Gouy–Chapman (URMGC) theories and with those of HNC/MSA in the restricted primitive model (RPM) to assess the importance of size-asymmetry effects. One of the most striking characteristics found is that, contrary to the general belief, away from the point of zero charge the properties of an asymmetric electrical double layer (EDL) are not those corresponding to a symmetric electrolyte with the size and charge of the counterion, i.e., counterions do not always dominate. This behavior suggests the existence of a new phenomenology in the EDL that genuinely belongs to a more realistic size-asymmetric model where steric correlations are taken into account consistently. Such novel features cannot be described by traditional mean-field theories such as MGC, URMGC, or even by enhanced formalisms, such as HNC/MSA, if they are based on the RPM.
Mechanism of Cu diffusion in porous low-κ dielectrics
Authors: Rodriguez Oscar R. , Cho Woojin , Saxena Ravi , Plawsky Joel L. , Gill William N.
Published: July 2005

This work is aimed at understanding the nature of the interactions between metal interconnects and nanoporous dielectrics in integrated circuits. Electrical testing of metal-insulator-semiconductor capacitors is used to assess Cu diffusion and charge injection in the dielectric in the presence of an electric field. We show that the effect of surface chemistry in Cu diffusion is stronger than the effect of porosity. The surface chemistry or the amount of organic content in a porous dielectric depends on the pore morphology and it is limited by steric hindrance during dielectric fabrication. Furthermore, we show that the reinclusion of organic groups in a damaged dielectric results in an increasing resistance to Cu diffusion. We propose that a combination of moisture-related species in the dielectric and interfacial oxygen oxidizes Cu. The copper oxide acts as a source for Cu ions available for diffusion. A quantitative analysis of Cu drift in nanoporous dielectrics that shows the importance of surface chemistry and porosity is presented and the mechanism of metal diffusion and charge injection in nanoporous dielectrics is discussed.
Phase and interface behaviors in type-I and type-V Lennard-Jones mixtures: Theory and simulations
Authors: Mejía Andrés , Pàmies Josep C. , Duque Daniel , Segura Hugo , Vega Lourdes F.
Published: July 2005

Density gradient theory (DGT) and molecular-dynamics (MD) simulations have been used to predict subcritical phase and interface behaviors in type-I and type-V equal-size Lennard-Jones mixtures. Type-I mixtures exhibit a continuum critical line connecting their pure critical components, which implies that their subcritical phase equilibria are gas liquid. Type-V mixtures are characterized by two critical lines and a heteroazeotropic line. One of the two critical lines begins at the more volatile pure component critical point up to an upper critical end point and the other one comes from the less volatile pure component critical point ending at a lower critical end point. The heteroazeotropic line connects both critical end points and is characterized by gas-liquid-liquid equilibria. Therefore, subcritical states of this type exhibit gas-liquid and gas-liquid-liquid equilibria. In order to obtain a correct characterization of the phase and interface behaviors of these types of mixtures and to directly compare DGT and MD results, the global phase diagram of equal-size Lennard-Jones mixtures has been used to define the molecular parameters of these mixtures. According to our results, DGT and MD are two complementary methodologies able to obtain a complete and simultaneous prediction of phase equilibria and their interfacial properties. For the type of mixtures analyzed here, both approaches have shown excellent agreement in their phase equilibrium and interface properties in the full concentration range.
Deposition of microcrystalline silicon prepared by hot-wire chemical-vapor deposition: The influence of the deposition parameters on the material properties and solar cell performance
Authors: Klein Stefan , Finger Friedhelm , Carius Reinhard , Stutzmann Martin
Published: July 2005

Microcrystalline silicon (μc-Si:H) of superior quality can be prepared using the hot-wire chemical-vapor deposition method (HWCVD). At a low substrate temperature (TS) of 185 °C excellent material properties and solar cell performance were obtained with spin densities of 6×1015cm−3 and solar cell efficiencies up to 9.4%, respectively. In this study we have systematically investigated the influence of various deposition parameters on the deposition rate and the material properties. For this purpose, thin films and solar cells were prepared at specific substrate and filament temperatures and deposition pressures (pD), covering the complete range from amorphous to highly crystalline material by adjusting the silane concentration. The influence of these deposition parameters on the chemical reactions at the filament and in the gas phase qualitatively explains the behavior of the structural composition and the formation of defects. In particular, we propose that the deposition rate is determined by the production of reactive species at the filament and a particular atomic-hydrogen-to-silicon ratio is found at the microcrystalline/amorphous transition. The structural, optical, and electronic properties were studied using Raman and infrared spectroscopies, optical-absorption measurements, electron-spin resonance, and dark and photoconductivities. These experiments show that higher TS and pD lead to a deterioration of the material quality, i.e., much higher defect densities, oxygen contaminations, and SiH absorption at 2100cm−1. Similar to plasma enhanced chemical-vapor deposition material, μc-Si:H solar cells prepared with HW i layers show increasing open circuit voltages (Voc) with increasing silane concentration and best performance is achieved near the transition to amorphous growth. Such solar cells prepared at low TS exhibit very high Voc up to 600 mV and fill factors above 70% with i layers prepared by HWCVD.
Experimental study of Richtmyer-Meshkov instability induced by cylindrical shock waves
Authors: Hosseini S. H. R. , Takayama K.
Published: July 2005

The paper describes the results of holographic interferometric flow visualization of the Richtmyer-Meshkov instability induced by cylindrical shock waves propagating across cylindrical interfaces. Experiments were conducted in an annular coaxial vertical diaphragmless shock tube, which can produce converging cylindrical shock waves with minimum disturbances. The shock wave converged and interacted with a cylindrical soap bubble filled with He, Ne, air, Ar, Kr, Xe, or SF6. The soap bubble was placed coaxially in the test section. The effects of density variation on the Richtmyer-Meshkov instability for a wide range of Atwood numbers were determined. Pressure histories at different radii during the shock wave implosion and reflection from the center were measured. Double-exposure holographic interferometry was used and the motion of the converging shock wave and its interaction with the gaseous interface were visualized. The variation of the pressure at the center with interface Atwood number for constant incident shock Mach number was studied. It is found that the dominant mechanism limiting the maximum pressure at the center of convergence is related to the instability of the converging shock wave induced by its interaction with the interface. A short time after the impulsive acceleration, the interface started deforming, and the growth of these perturbations is described. The results show that after diverging shock wave interaction, the reshocked cylindrical interfaces have a higher growth rate of the turbulent mixing zone than that of the reshocked interface in a plane geometry reported by previous works.
Solid-state thermionics and thermoelectrics in the ballistic transport regime
Authors: Humphrey T. E. , O’Dwyer M. F. , Zhang C. , Lewis R. A.
Published: July 2005

It is shown that the equations for electrical current in solid-state thermionic and thermoelectric devices converge for devices with a width equal to the mean free path of electrons, yielding a common expression for the intensive electronic efficiency in the two types of devices. This result is used to demonstrate that the material parameters for thermionic and thermoelectric refrigerators are equal, rather than differing by a multiplicative factor as previously thought.