bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetoimpedanzmethode zur Detektion von Materialfehlern in Aluminiumbauteilen des Airbus A-380 (Magneto-Impedance Method for Defect Detection in Aluminium Components of the Airbus A-380)
Authors: von Kreutzbruck Marc , Allweins Kai
Published: September 2004

Es wird eine Magnetoimpedanzmethode zur Detektion von extrem tief liegenden Materialfehlern in Aluminiumkomponenten des Flugzeugbaus vorgestellt. Ausgehend von induzierten Wechselströmen werden die durch Materialfehler erzeugten Inhomogenitäten in der Magnetfeldverteilung detektiert. Hierzu kommt höchstempfindliche Magnetosensorik (z.B. SQUID) zum Einsatz, die es ermöglicht, geringe Abweichungen in der Amplituden- wie auch Phaseninformation zu bestimmen. Wesentlicher Bestandteil für eine zuverlässige Materialfehlerdetektion ist die erfolgreiche Trennung der magnetischen Signatur des Fehlers von den überlagerten Feldvariationen, die durch sonstige Komponenten verursacht werden (z.B. Titanbolzen). Neben der simulationsgestützten Bestimmung von optimalen Anregungsfrequenzen und den Fehler-Separationsmethoden wird von Messungen an über 60 mm starken Aluminiumstrukturen berichtet.
Bodenfeuchtemessung mittels Impedanzspektroskopie (Soil Moisture Measurement with Impedance Spectroscopy)
Authors: Kanoun Olfa , Tetyuev Andrey , Tränkler Hans-Rolf
Published: September 2004

Verfahren zur Bestimmung der Bodenfeuchte haben diverse Nachteile aufgrund hoher Kosten und der Abhängigkeit der gemessenen Signale von den Materialeigenschaften des Bodens. Durch die Nutzung der Methode der Impedanzspektroskopie kann ein höherer Informationsgehalt im frequenzabhängigen Real- und Imaginärteil der Dielektrizitätskonstante bei der gesuchten Bodenfeuchte generiert werden. Untersuchungen zeigen, dass mathematische und physikalische Methoden für die Signalverarbeitung bei der bodenartunabhängigen Bodenfeuchtemessung genutzt werden können.
Continuous Crude Oil Characterization by a Radio Frequency Resonator (Kontinuierliche Rohöl-Bewertung mittels eines Hochfrequenzresonators)
Authors: Gasch Armin , Riegler Peter , Powell Steve
Published: September 2004

Determining the component fractions in flowing fluids is of paramount technical interest in the process industry. One of the main challenging measurement tasks is the determination of the crude oil, water and gas fractions in the offshore oil production. Out of the possible measurement principles electromagnetic interaction is promising for cases where the fluid components have distinct dielectric properties. In this paper a new type of non-invasive multiphase meter is described which is based on a radio-frequency dielectric measurement principle using a slow-wave resonator. The data analysis is based on a theoretical treatment of the metering system. By deriving an exact relation between the dielectric properties of the flow components and the resulting resonance spectrum the individual volume fractions can be obtained from the measuring data. The theoretical model is verified by experimental results.
Die akustische Impedanz als Messgröße zur Charakterisierung flüssiger Stoffsysteme (Acoustic Impedance as a Process Variable to Characterize Liquids)
Authors: Henning Bernd
Published: September 2004

Die elektrische Impedanzmessung ist heute in einem weiten Frequenzbereich technisch möglich und wird vielfach zur Materialcharakterisierung eingesetzt. Neben den elektrischen und optischen Messverfahren verfügen aber auch gerade die akustischen Messverfahren über vorteilhafte Applikationseigenschaften wie Robustheit und geringe Wartungsanforderungen. Die zuverlässige Bestimmung der Schallkennimpedanz als eine der drei akustischen Stoffkenngrößen erweist sich aber noch heute als sehr diffizil, wie im Folgenden gezeigt wird.
Anwendung der Impedanzspektrometrie zur Selbstüberwachung amperometrischer Gassensoren (Use of Impedance Spectrometry for Self-Monitoring of Amperometric Gas Sensors)
Authors: Horn Michael
Published: September 2004

Die Empfindlichkeit amperometrischer Gassensoren ist proportional zur Größe der elektrochemisch aktiven Fläche. Die Größe dieser Fläche verringert sich durch Ablagerungen und Verschmutzung des Katalysators und sollte deshalb während des Betriebes automatisch überwacht werden. Da die Doppelschichtkapazität und der Durchtrittsleitwert ebenfalls proportional zur Elektrodenfläche sind, können diese durch impedanzspektrometrische Messungen bestimmt und zur Selbstüberwachung der Sensoren herangezogen werden. Die Bestimmung der Größe der Doppelschichtkapazität erfolgt durch modellgestützte Auswertung der Impedanzspektren der gesamten Messanordnung, deren Ersatzschaltbild durch einen Satz von insgesamt neun Modellparametern gekennzeichnet ist gekennzeichnet ist. Die Analyse dieser neun Parameter zeigt, dass davon nur zwei exemplarspezifisch sind und während des Betriebes bestimmt werden müssen; die anderen sind typspezifisch bzw. im gewählten Frequenzbereich nicht relevant.
Diagnose von Gerätebatterien mit Impedanzspektrometrie (Diagnosis of Portable Secondary Batteries by Impedance Spectroscopy)
Authors: Tröltzsch Uwe , Kanoun Olfa , Tränkler Hans-Rolf
Published: September 2004

Zur Charakterisierung von Alterungseffekten von Gerätebatterien ist Impedanzspektroskopie eine der aussichtsreichsten Methoden, insbesondere bei der Trennung verschiedener Alterungseffekte. Bei einem breiten Einsatz der Impedanzspektroskopie im Online-Betrieb ergeben sich spezielle Anforderungen. Messzeiten müssen trotz niedriger Frequenzen kurz sein, was durch die Verwendung mehrfrequenter Signale erreicht wird. Modelle müssen mit verschiedenen Batterietypen verwendbar sein, weshalb Modelle von Mischelektroden Anwendung finden. Die Modellparameter müssen ohne Nutzerinteraktion bestimmt werden, daher wird eine Kombination von Evolutionären Verfahren und dem Levenberg-Marquardt-Algorithmus verwendet. Experimentelle Untersuchungen an einer Lithium-Ion-Zelle zeigen die Eignung der Impedanzspektroskopie zur Charakterisierung von Alterungseffekten. Eine Verringerung der Kapazität um 14% nach 230 Entlade-/Ladezyklen sowie eine Veränderung des Elektrolytwiderstandes, des Durchtrittswiderstandes und des Warburgkoeffizienten um jeweils etwa 60% wurden beobachtet.
Elektrische Impedanztomographie – ein Verfahren zur Überwachung der regionalen Lungenfunktion (Electrical Impedance Tomography – a Method for Monitoring Regional Lung Function)
Authors: Frerichs Inéz
Published: September 2004

Elektrische Impedanztomographie (EIT) ist ein neues bildgebendes Verfahren, das die Perspektive besitzt, in der Zukunft in der klinischen Medizin zur Überwachung von beatmeten Intensivpatienten eingesetzt zu werden. Das Potential der EIT in dieser Anwendung bezieht sich auf die Fähigkeit der Methode, nichtinvasiv und kontinuierlich die regionale Lungenventilation direkt am Krankenbett zu erfassen. Diese Fähigkeit der EIT wird durch Ergebnisse aus experimentellen und klinischen Untersuchungen dokumentiert.
X-Ray Survival Characteristics and Genetic Analysis for Nine Saccharomyces Deletion Mutants That Show Altered Radiation Sensitivity
Authors: Game John C , Williamson Marsha S , Baccari Clelia
Published: September 2004

The availability of a genome-wide set of Saccharomyces deletion mutants provides a chance to identify all the yeast genes involved in DNA repair. Using X rays, we are screening these mutants to identify additional genes that cause increased sensitivity to the lethal effects of ionizing radiation. For each mutant identified as sensitive, we are confirming that the sensitivity phenotype cosegregates with the deletion allele and are obtaining multipoint survival-vs.-dose assays in at least one homozygous diploid and two haploid strains. We present data for deletion mutants involving the genes DOT1, MDM20, NAT3, SPT7, SPT20, GCN5, HFI1, DCC1, and VID21/EAF1 and discuss their potential roles in repair. Eight of these genes cause a clear radiation-sensitive phenotype when deleted, but the ninth, GCN5, results in at most a borderline phenotype. None of the deletions confer substantial sensitivity to ultraviolet radiation, although one or two may confer marginal sensitivity. The DOT1 gene is of interest because its only known function is to methylate one lysine residue in the core of the histone H3 protein. We find that histone H3 mutants (supplied by K. Struhl) in which this residue is replaced by other amino acids are also X-ray sensitive, which confirms that methylation of the lysine-79 residue is required for effective repair of radiation damage.
Survey and Analysis of Microsatellites in the Silkworm, Bombyx mori
Authors: Prasad M Dharma , Muthulakshmi M , Madhu M , Archak Sunil , Mita K , Nagaraju J
Published: September 2004

We studied microsatellite frequency and distribution in 21.76-Mb random genomic sequences, 0.67-Mb BAC sequences from the Z chromosome, and 6.3-Mb EST sequences of Bombyx mori. We mined microsatellites of ≥15 bases of mononucleotide repeats and ≥5 repeat units of other classes of repeats. We estimated that microsatellites account for 0.31% of the genome of B. mori. Microsatellite tracts of A, AT, and ATT were the most abundant whereas their number drastically decreased as the length of the repeat motif increased. In general, tri- and hexanucleotide repeats were overrepresented in the transcribed sequences except TAA, GTA, and TGA, which were in excess in genomic sequences. The Z chromosome sequences contained shorter repeat types than the rest of the chromosomes in addition to a higher abundance of AT-rich repeats. Our results showed that base composition of the flanking sequence has an influence on the origin and evolution of microsatellites. Transitions/transversions were high in microsatellites of ESTs, whereas the genomic sequence had an equal number of substitutions and indels. The average heterozygosity value for 23 polymorphic microsatellite loci surveyed in 13 diverse silkmoth strains having 2–14 alleles was 0.54. Only 36 (18.2%) of 198 microsatellite loci were polymorphic between the two divergent silkworm populations and 10 (5%) loci revealed null alleles. The microsatellite map generated using these polymorphic markers resulted in 8 linkage groups. B. mori microsatellite loci were the most conserved in its immediate ancestor, B. mandarina, followed by the wild saturniid silkmoth, Antheraea assama.
Testing for Hardy-Weinberg Equilibrium in Samples With Related Individuals
Authors: Bourgain Catherine , Abney Mark , Schneider Daniel , Ober Carole , McPeek Mary Sara
Published: September 2004

When the classical χ2 goodness-of-fit test for Hardy-Weinberg (HW) equilibrium is used on samples with related individuals, the type I error can be greatly inflated. In particular the test is inappropriate in population isolates where the individuals are related through multiple lines of descent. In this article, we propose a new test for HW (the QL-HW test) suitable for any sample with related individuals, including large inbred pedigrees, provided that their genealogy is known. Performed conditional on the pedigree structure, the QL-HW test detects departures from HW that are not due to the genealogy. Because the computation of the QL-HW test becomes intractable for very polymorphic loci in large inbred pedigrees, a simpler alternative, the GCC-HW test, is also proposed. The statistical properties of the QL-HW and GCC-HW tests are studied through simulations considering a sample of independent nuclear families, a sample of extended outbred genealogies, and samples from the Hutterite population, a North American highly inbred isolate. Finally, the method is used to test a set of 143 biallelic markers spanning 82 genes in this latter population.
Bayesian Association-Based Fine Mapping in Small Chromosomal Segments
Authors: Sillanpää Mikko J , Bhattacharjee Madhuchhanda
Published: September 2004

A Bayesian method for fine mapping is presented, which deals with multiallelic markers (with two or more alleles), unknown phase, missing data, multiple causal variants, and both continuous and binary phenotypes. We consider small chromosomal segments spanned by a dense set of closely linked markers and putative genes only at marker points. In the phenotypic model, locus-specific indicator variables are used to control inclusion in or exclusion from marker contributions. To account for covariance between consecutive loci and to control fluctuations in association signals along a candidate region we introduce a joint prior for the indicators that depends on genetic or physical map distances. The potential of the method, including posterior estimation of trait-associated loci, their effects, linkage disequilibrium pattern due to close linkage of loci, and the age of a causal variant (time to most recent common ancestor), is illustrated with the well-known cystic fibrosis and Friedreich ataxia data sets by assuming that haplotypes were not available. In addition, simulation analysis with large genetic distances is shown. Estimation of model parameters is based on Markov chain Monte Carlo (MCMC) sampling and is implemented using WinBUGS. The model specification code is freely available for research purposes from http://www.rni.helsinki.fi/~mjs/.
A Mechanistic Model for Genetic Machinery of Ontogenetic Growth
Authors: Wu Rongling , Wang Zuoheng , Zhao Wei , Cheverud James M
Published: September 2004

Two different genetic mechanisms can be proposed to explain variation in growth trajectories. The allelic sensitivity hypothesis states that growth trajectory is controlled by the time-dependent expression of alleles at the deterministic quantitative trait loci (dQTL) formed during embryogenesis. The gene regulation hypothesis states that the differentiation in growth process is due to the opportunistic quantitative trait loci (oQTL) through their mediation with new developmental signals. These two hypotheses of genetic control have been elucidated in the literature. Here, we propose a new statistical model for discerning these two mechanisms in the context of growth trajectories by integrating growth laws within a QTL-mapping framework. This model is developed within the maximum-likelihood context, implemented with a grid approach for estimating the genomic positions of the deterministic and opportunistic QTL and the simplex algorithm for estimating the growth curve parameters of the genotypes at these QTL and the parameters modeling the residual (co)variance matrix. Our model allows for extensive hypothesis tests for the genetic control of growth processes and developmental events by these two types of QTL. The application of this new model to an F2 progeny in mice leads to the detection of deterministic and opportunistic QTL on chromosome 1 for mouse body mass growth. The estimates of QTL positions and effects from our model are broadly in agreement with those by traditional interval-mapping approaches. The implications of this model for biological and biomedical research are discussed.
Involvement of Subcortical Structures in the Preparation of Self-Paced Movement
Authors: Paradiso Guillermo , Cunic Danny , Chen Robert
Published: September 2004

Abstract Although it has long been suggested that the basal ganglia and thalamus are involved in movement planning and preparation, there was little direct evidence in humans to support this hypothesis. Deep brain stimulation (DBS) is a well-established treatment for movement disorders such as Parkinson's disease, tremor, and dystonia. In patients undergoing DBS surgery, we recorded simultaneously from scalp contacts and from electrodes surgically implanted in the subthalamic nucleus (STN) of 13 patients with Parkinson's disease and in the “cerebellar” thalamus of 5 patients with tremor. The aim of our studies was to assess the role of the cortico-basal ganglia-thalamocortical loop through the STN and the cerebello-thalamocortical circuit through the “cerebellar” thalamus in movement preparation. The patients were asked to perform self-paced wrist extension movements. All subjects showed a cortical readiness potential (RP) with onset ranging between 1.5 to 2s before the onset of movement. Subcortical RPs were recorded in 11 of 13 with electrodes in the STN and in 4 of 5 patients with electrodes in the thalamus. The onset time of the STN and thalamic RPs were not significantly different from the onset time of the scalp RP. The STN and thalamic RPs were present before both contralateral and ipsilateral hand movements. Postoperative MRI studies showed that contacts with maximum RP amplitude generally were inside the target nucleus. These findings indicate that both the basal ganglia and the cerebellar circuits participate in movement preparation in parallel with the cortex.
Kinetic energy distributions and line profile measurements of dissociation products of water upon electron impact
Authors: Makarov Oleg P. , Ajello Joseph M. , Vattipalle Prahlad , Kanik Isik , Festou M. C. , Bhardwaj Anil
Published: September 2004

The Doppler line profiles of H Ly‐α (1216 Å) and O I (1302 Å and 1152 Å) resulting from electron impact dissociative excitation of H2O have been measured with a high‐resolution (λ/Δλ = 50,000) ultraviolet spectrometer. The line profiles are used to calculate the kinetic energy distribution of the hydrogen atoms produced in dissociative excitation and ionization of H2O at electron impact energies 25, 35, and 100 eV. Three distinct populations of H(2p) atoms were found. The kinetic energy of hydrogen atoms is found to have contributions from a low‐energy component, with a mean energy of ∼0.2 eV at all the three electron impact energies. In addition, a medium‐energy component appears with a mean energy of ∼2.0 eV for 35 eV electrons, and a high‐energy component, ∼7 eV, for 100 eV electrons. The measurement of O I (1302 Å) and O I (1152 Å) line profiles indicate that the kinetic energy of excited O I atoms is very small (∼1 eV or less) at all electron impact energies. Most of the energy released in dissociation is found in the translational energy of the hydrogen atoms. The excitation functions of H Ly‐α, O I (1302 Å) feature of oxygen, and A(0) − X(0) molecular band of hydroxyl near 3050 Å from threshold to 600 V were also measured. The spectrum (1.0 Å FWHM) of the rotational structure of OH (A − X) from electron impact dissociation indicates a high degree of rotational excitation, which is almost identical to the rotational structure from dissociative recombination of H2O+. The results presented in this paper have important applications to planetary bodies, like comets, icy satellites of outer planets, Saturn's magnetosphere, and rings, all of which have H2O and its daughter products in large amount.
Spatial distribution and size evolution of particles in Asian outflow: Significance of primary and secondary aerosols during ACE‐Asia and TRACE‐P
Authors: McNaughton Cameron S. , Clarke Antony D. , Howell Steven G. , Moore Kenneth G. , Brekhovskikh Vera , Weber Rodney J. , Orsini Douglas A. , Covert David S. , Buzorius Gintautas , Brechtel Fred J. , Carmichael Gregory R. , Tang Youhua , Eisele Fred L. , Mauldin R. Lee , Bandy Alan R. , Thornton Donald C. , Blomquist Byron
Published: September 2004

Quasi‐Lagrangian aircraft measurements above the Yellow Sea, East China Sea, and Sea of Japan revealed synoptic‐scale secondary aerosol formation and condensational growth during the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) and Transport and Chemical Evolution over the Pacific (TRACE‐P) experiment. This occurred in the presence of pollution and mineral dust aerosol surface areas as high as 1200 μm2 cm−3. Concentrations of sulfuric acid generally appeared insufficient for binary nucleation, but observations, models, and theory are consistent with a ternary nucleation mechanism involving H2SO4‐H2O‐NH3. Growth rates of ∼2 nm h−1 can be explained by the condensation of sulfuric acid at a rate of 2 ± 1 × 106 molecules cm−3 s−1. Aerosol volatility suggested increasing neutralization of the aerosol during growth. Size distribution measurements suggest that weak (mean condensation nuclei (CN) 3–13 nm ≈ 500 cm−3) new particle production was a common occurrence in the region. However, new particle production was enhanced by ∼1 order of magnitude (mean CN 3–13 nm ≈ 5000 cm−3) in postfrontal air masses associated with offshore flow during cloud‐free conditions. Fog and clouds appear to be regionally important in modulating nucleation events through scavenging of secondary aerosol and through depletion of gas‐phase precursors through enhanced heterogeneous chemistry. Our results indicate that only 10–30% of the total aerosol population consists of aged secondary aerosols after ∼2 days of transport from source regions. In spite of their high production during nucleation events, secondary aerosols advected out over the Pacific Ocean will have a small impact upon indirect forcing and a negligible impact upon direct forcing compared to primary aerosol emissions and the species that condense upon them.
LINKS BETWEEN LONG‐LIVED HOT SPOTS, MANTLE PLUMES, D″, AND PLATE TECTONICS
Authors: Jellinek A. Mark , Manga Michael
Published: September 2004

The existence, spatial distribution, and style of volcanism on terrestrial planets is an expression of their internal dynamics and evolution. On Earth a physical link has been proposed between hot spots, regions with particularly persistent, localized, and high rates of volcanism, and underlying deep mantle plumes. Such mantle plumes are thought to be constructed of large spherical heads and narrow trailing conduits. This plume model has provided a way to interpret observable phenomena including the volcanological, petrological, and geochemical evolution of ocean island volcanoes, the relative motion of plates, continental breakup, global heat flow, and the Earth's magnetic field within the broader framework of the thermal history of our planet. Despite the plume model's utility the underlying dynamics giving rise to hot spots as long‐lived stable features have remained elusive. Accordingly, in this review we combine results from new and published observational, analog, theoretical, and numerical studies to address two key questions: (1) Why might mantle plumes in the Earth have a head‐tail structure? (2) How can mantle plumes and hot spots persist for large geological times? We show first that the characteristic head‐tail structure of mantle plumes, which is a consequence of hot upwellings having a low viscosity, is likely a result of strong cooling of the mantle by large‐scale stirring driven by plate tectonics. Second, we show that the head‐tail structure of such plumes is a necessary but insufficient condition for their longevity. Third, we synthesize seismological, geodynamic, geomagnetic, and geochemical constraints on the structure and composition of the lowermost mantle to argue that the source regions for most deep mantle plumes contain dense, low‐viscosity material within D″ composed of partial melt, outer core material, or a mixture of both (i.e., a “dense layer”). Fourth, using results from laboratory experiments on thermochemical convection and new theoretical scaling analyses, we argue that the longevity of mantle plumes in the Earth is a consequence of the interactions between plate tectonics, core cooling, and dense, low‐viscosity material within D″. Conditions leading to Earth‐like mantle plumes are highly specific and may thus be unique to our own planet. Furthermore, long‐lived hot spots should not a priori be anticipated on other terrestrial planets and moons. Our analysis leads to self‐consistent predictions for the longevity of mantle plumes, topography on the dense layer, and composition of ocean island basalts that are consistent with observations.
Impact of hurricanes on the flux of rainwater and Cape Fear River water dissolved organic carbon to Long Bay, southeastern United States
Authors: Avery G. Brooks , Kieber Robert J. , Willey Joan D. , Shank G. Christopher , Whitehead Robert F.
Published: September 2004

The hurricane flux of rain and river water dissolved organic carbon (DOC) to Long Bay located on the southeastern coast of the United States was determined for four hurricanes that made landfall in the Cape Fear region of North Carolina. Riverine flux of DOC following hurricanes Fran (1996) and Floyd (1999) represented one third and one half of the entire annual river flux of DOC to Long Bay, respectively. The majority of this DOC was recalcitrant and not available for biological consumption. The high flux of DOC from hurricane Floyd resulted from extremely high precipitation amounts (in excess of 50 cm) associated with the hurricane and subsequent flooding. High riverine DOC fluxes were observed following hurricane Fran but not hurricanes Bertha (1996) and Bonnie (1998). The westerly path of Fran deposited rain inland along the Cape Fear River watershed, causing high river flow conditions, while Bonnie and Bertha took an eastern path, resulting in a minimal effect to the Cape Fear River flow rates. The rainwater flux of total DOC to Long Bay from the four hurricanes was not as dramatic as that observed for riverine fluxes. However, unlike river water DOC that is refractory, rainwater DOC is highly labile. Rainwater from the four hurricanes in this study deposited 2–5 times the DOC deposited in an average storm. This represented a flux of 3–9% of the entire annual budget of bioavailable DOC to Long Bay being deposited over a 1 or 2 day period, likely spurring short‐term secondary productivity following the hurricanes.
Seawater‐peridotite interactions: First insights from ODP Leg 209, MAR 15°N
Authors: Bach Wolfgang , Garrido Carlos J. , Paulick Holger , Harvey Jason , Rosner Martin
Published: September 2004

We present first results of a petrographic study of hydrothermally altered peridotites drilled during Ocean Drilling Program (ODP) Leg 209 in the 15°20′N fracture Zone area on the Mid‐Atlantic Ridge (MAR). We find that serpentinization is extensive at all drill sites. Where serpentinization is incomplete, phase relations indicate two major reaction pathways. One is reaction of pyroxene to talc and tremolite, and the other is reaction of olivine to serpentine, magnetite, and brucite. We interpret these reactions in the light of recent peridotite‐seawater reaction experiments and compositions of fluids venting from peridotite massifs at a range of temperatures. We suggest that the replacement of pyroxene by talc and tremolite takes place at temperatures >350°–400°C, where olivine is stable. The breakdown of olivine to serpentine, magnetite, and brucite is favored at temperatures below 250°C, where olivine reacts faster then pyroxene. High‐temperature hydrothermal fluids venting at the Logatchev and Rainbow sites are consistent with rapid reaction of pyroxene and little or no reaction of olivine. Moderate‐temperature fluids venting at the Lost City site are consistent with ongoing reaction of olivine to serpentine and brucite. Many completely serpentinized peridotites lack brucite and talc because once the more rapidly reacting phase is exhausted, interaction with the residual phase will change fluid pH and silica activity such that brucite or talc react to serpentine. At two sites we see strong evidence for continued fluid flow and fluid‐rock interaction after serpentinization was complete. At Site 1268, serpentinites underwent massive replacement by talc under static conditions. This reaction requires either removal of Mg from or addition of Si to the system. We propose that the talc‐altered rocks are Si‐metasomatized and that the source of Si is likely gabbro‐seawater reaction or breakdown of pyroxene deeper in the basement. The basement at Site 1268 is heavily veined, with talc and talc‐oxide‐sulfide veins being the most common vein types. It appears that the systems evolved from reducing (oxygen fugacity buffered by magnetite‐pyrrhotite‐pyrite and lower) to oxidizing (dominantly hematite). We propose that this transition is indicative of high fluid flux under retrograde conditions and that the abundance of hematite may relate to the Ca‐depleted nature of the basement that prevents near‐quantitative removal of seawater sulfate by anhydrite precipitation. At site 1272 we find abundant iowaite partly replacing brucite. While this is the first report of iowaite from a mid‐ocean ridge setting, its presence indicates, again, fairly oxidizing conditions. Our preliminary results indicate that peridotite‐seawater and serpentinite‐seawater interactions can take place under a wider range of temperature and redox conditions than previously appreciated.
Geophysical evidence for chemical variations in the Australian Continental Mantle
Authors: van Gerven Luuk , Deschamps Frédéric , van der Hilst Robert D.
Published: September 2004

The relative density‐to‐shear velocity scaling (ζ) provides a diagnostic for the presence of compositional variations in the mantle. We invert shear‐wave velocity from a recent 3‐D model and gravity anomalies for radial profiles of ζ of the uppermost mantle beneath Australia. We performed calculations for the three major tectonic provinces that constitute the continent, and found significant differences between them. The ζ profile for the Phanerozoic region can be explained by thermal variations alone. In contrast, negative values of ζ suggest that variations in composition are important between ∼75 and ∼150 km depth in the Proterozoic continental lithosphere (central Australia). It is likely that chemical variations are also required to explain the inferences for the Archean craton (west Australia), but poor tomographic resolution precludes a definitive conclusion. The scaling factors found are consistent with chemical depletion of deep Precambrian lithosphere, which supports a tectosphere model for the Australian continental roots.
The seasonal cycle of N2O
Authors: Liao Ting , Camp Charles D. , Yung Yuk L.
Published: September 2004

We have carried out an empirical study of the seasonal cycle of nitrous oxide (N2O) using the data archived by the National Oceanic and Atmospheric Administration – Climate Monitoring and Diagnostics Laboratory (NOAA‐CMDL) Global Cooperative Air Sampling Network from 1977 to 2000. In order to isolate the seasonal cycle, we first detrended the data using least square polynomial fits. The remaining variability was averaged to extract the seasonal cycle, which has an amplitude of about 0.8 ppbv. The statistical significance of the seasonal signal was established using the multitaper method and Welch's method for power spectrum analysis.
Altered hydrologic feedback in a warming climate introduces a “warming hole”
Authors: Pan Zaitao , Arritt Raymond W. , Takle Eugene S. , Gutowski William J. , Anderson Christopher J. , Segal Moti
Published: September 2004

In the last 25 years of the 20th century most major land regions experienced a summer warming trend, but the central U.S. cooled by 0.2–0.8 K. In contrast most climate projections using GCMs show warming for all continental interiors including North America. We examined this discrepancy by using a regional climate model and found a circulation‐precipitation coupling under enhanced greenhouse gas concentrations that occurs on scales too small for current GCMs to resolve well. Results show a local minimum of warming in the central U.S. (a “warming hole”) associated with changes in low‐level circulations that lead to replenishment of seasonally depleted soil moisture, thereby increasing late‐summer evapotranspiration and suppressing daytime maximum temperatures. These regional‐scale feedback processes may partly explain the observed late 20th century temperature trend in the central U.S. and potentially could reduce the magnitude of future greenhouse warming in the region.
Crustal structure variations in northeast India from converted phases
Authors: Kumar M. Ravi , Raju P. Solomon , Devi E. Uma , Saul J. , Ramesh D. S.
Published: September 2004

Teleseismic receiver functions from a ten station network deployed in northeast India region sampling the Shillong plateau, Mikir Hills, Himalayan foredeep and the Himalayan convergence zone, are analyzed to obtain the crustal structure in this seismically active but less studied region. The Shillong plateau and Mikir hills, away from the convergent margins, reveal remarkably simple crust with thickness (∼35 km) and Poisson's ratio (∼0.25), akin to the Indian shield values. A surprisingly thin crust for the uplifted Shillong plateau may be explained invoking presence of an uncompensated crust that popped up in response to tectonic forces. In contrast, crustal signatures from Assam valley suggest a thicker crust and higher Poisson's ratio with evidences for a dipping Moho. Predictably, the crust is much thicker and complicated in the eastern Himalaya further north, with values in excess of 50 km.
Finite gyroradius theory of drift compressional modes
Authors: Crabtree Chris , Chen Liu
Published: September 2004

A dispersion relation for ultralow frequency drift compressional modes in high pressure plasmas with finite gyroradius is derived from the linearized gyrokinetic‐Maxwell equations with cold electrons and narrow eigenmode localization width along the field line. The dispersion relation demonstrates instability under two different conditions: 1) when the density gradient and proton temperature gradient are in opposite directions, or 2) when the magnetic guiding center drift is reversed with respect to the proton diamagnetic drift, i.e., drift reversal, which could occur during periods of strong magnetospheric disturbance. Furthermore, it is found that the most unstable modes have short azimuthal wavelengths comparable to the proton gyroradius.
Seasonal differences in extratropical potential vorticity variability at tropopause levels
Authors: Liniger M. A. , Davies H. C.
Published: September 2004

The distribution of extratropical potential vorticity (PV) on isentropic surfaces that transect the tropopause is a key feature of planetary‐scale teleconnection patterns, synoptic‐scale weather systems, and mesoscale stratosphere‐troposphere exchange. Here a Northern Hemisphere January and July climatology is presented for the mean and variability patterns of the PV using the so‐called European Centre for Medium‐Range Weather Forecasts reanalysis‐15 (ERA‐15) data set. It is derived taking into account the strong seasonal cycle of the tropopause height and the sharp quasi‐latitudinal gradient of PV on the isentropic surfaces together with the accompanying bimodality in the scale and amplitude of positive and negative anomalies. The bimodality is both emphasized and circumvented by comparing conventional standard deviation measures of the variability with those of separate depictions of the probability density function structures of positive and negative anomalies. It is shown that in winter the zonal heterogeneity is pronounced and the variability (e.g., storm track) patterns exhibit a rich spatial structure with marked differences between the Pacific and Atlantic. In contrast, in summer the heterogeneity on the lower stratospheric portion of the isentropic surfaces is much weaker, but there remain regions of high variability over oceanic regions on the tropospheric portion of the surfaces. The results relate directly to the structure and dynamics of storm tracks and their spatial and seasonal variation.
Gravity waves generated by convection in the Darwin area during the Darwin Area Wave Experiment
Authors: Alexander M. Joan , May Peter T. , Beres Jadwiga H.
Published: September 2004

We describe a model study of gravity wave generation by convection near Darwin during the Darwin Area Wave Experiment (DAWEX). We focus on an 7‐hour period on 17 November 2001 for our study which included a major Hector event over the Tiwi Islands followed by a continental convective outbreak that included a squall line to the southeast of Darwin. Our model is a dry version of a three‐dimensional (3‐D) mesoscale cloud resolving model with horizontally uniform background wind and stability fields. The model is forced with a spatially and temporally varying heating field representative of the convective latent heating in the area. We derive this heating field from 3‐D volumetric reflectivity from the precipitation radar located just north of Darwin at Gunn Point during DAWEX. The conversion from radar reflectivity to a 3‐D latent heating field requires numerous assumptions that do not allow a quantitative heating estimate but which do provide a very realistic measure of the spatial morphology and temporal variations of the latent heating. Gravity waves generated by convective heating are known to be very sensitive to these characteristics of the heating, so our resulting wave field is likely to be the most realistic possible description of the waves emitted from convection in the Darwin area. Uncertainty in the wave amplitudes is large both because the input forcing (heating) is uncertain and because the use of heating as the sole proxy for wave forcing leads to additional wave amplitude errors. We therefore compare the results of the model to other DAWEX measurements and previous modeling studies both to validate the waves in our model and to calibrate the wave amplitudes. Our study in turn aids in the interpretation of the other gravity wave measurements during DAWEX.
Interstation correlation of high‐latitude lower‐stratosphere gravity wave activity: Evidence for planetary wave modulation of gravity waves over Antarctica
Authors: Innis J. L. , Klekociuk A. R. , Vincent R. A.
Published: September 2004

Four years of operational radiosonde balloon flights, from three Australian stations in eastern Antarctica (Casey, 66.3°S, 110.0°E; Davis, 68.6°S, 78.0°E; and Mawson, 67.6°S, 62.9°E) are analyzed to derive lower‐stratosphere (12–20 km altitude) gravity wave information from perturbations in wind and temperature. Gravity wave activity and seasonal behavior was found to be similar to that seen in earlier studies from Antarctica. Interstation comparisons of zonal wind and gravity wave activity showed very high correlations throughout the entire data set, between Mawson and Davis stations (∼600 km distant), with a lag near 0.5 days. The correlations between Casey and Davis (1400 km apart) were lower but still significant, with a lag near 1 day. There is no significant correlation between stratospheric gravity wave activity and surface winds. Our results suggest a pattern of winds and waves moving eastward over the stations with a speed near 15 m s−1. As this is comparable to planetary wave speeds, we interpret our results as being evidence for a significant planetary wave–induced modulation of the zonal wind and the gravity wave field, although we are unable to identify the mechanism by which this operates. Our work suggests that the high‐latitude lower‐stratosphere gravity wave fields are relatively uniform on spatial scales of 500–1000 km and on timescales of around 0.5–1 days.
Mars outflow channels: A reappraisal of the estimation of water flow velocities from water depths, regional slopes, and channel floor properties
Authors: Wilson Lionel , Ghatan Gil J. , Head James W. , Mitchell Karl L.
Published: September 2004

Methods used so far to assess the flow velocities of the water commonly assumed to be responsible for forming the major outflow channel systems on Mars have relied widely on various versions of the Manning equation. This has led to problems in allowing for the difference between the accelerations due to gravity on Mars and Earth and for the differences of scale between Martian floods and most river systems on Earth. We reanalyze the problem of estimating water flow velocities in Martian outflow channels using equations based on the Darcy‐Weisbach friction factor instead of the Manning n factor. We give simplified formulae appropriate to Mars for the Darcy‐Weisbach friction coefficient as a function of bedrock size distribution. For a given channel floor slope and water flood depth, similar mean flow velocities are implied for a wide range of values of the ratio of bed roughness to water depth relevant to Martian outflow channels. Using a recent rederivation of Manning's equation based on turbulence theory, we obtain a new value of 0.0545 s m−1/3 for the Manning n coefficient appropriate to Martian channels and show that previous analyses have generally overestimated (though in some cases underestimated) water flow velocities on Mars by a factor of order two. Combining the consequences of this flow velocity overestimate with likely overestimates of flow depth from assuming bank‐full flow, we show that discharges may have been overestimated by a factor of up to 25, leading to corresponding overestimates of subsurface aquifer permeabilities, rates of filling of depressions with water, and grain sizes of sediments on channel floors. Despite the availability of an improved value for the Manning n coefficient for Mars, we strongly recommend that modified forms of the original version of the Manning equation should be replaced by the modern form or, preferably, by the Darcy‐Weisbach equation in future work.
October–November 2003's space weather and operations lessons learned
Authors: Barbieri L. P. , Mahmot R. E.
Published: September 2004

The Sun‐Earth space weather related to sunspots NOAA 484, 486, and 488 affected a number of NASA spacecraft and instruments between mid‐October and early November 2003. Information available from Earth and space science missions indicate that about 59% of the spacecraft and about 18% of the instrument groups experienced some effect from the solar activity. This paper summarizes the impacts on spacecraft, instruments, and science data. The database that the paper is based on describes spacecraft and instrument effects observed as well as mission operators' preventive actions from 34 reporting missions. The database is Appendix A and provides additional material that could be of interest and that could be useful to satellite developers, operators, instrument managers, and scientists. The types of environmental effects observed were electronic upsets, housekeeping and science noise, proton degradation to solar arrays, upper atmosphere–induced changes to orbit dynamics, high levels of accumulated radiation, and proton heating. The paper develops best practices that are intended to foster continued and expanded feedback on the space environment in all mission phases, to promote designing to the mission's observing mode so that planning is appropriate to mission science goals, to distribute operational experience and lessons learned widely among both developing and operating missions, and to uniformly apply the developed knowledge base among NASA's missions.
Comparison of Efficacy of Reverse Remodeling and Clinical Improvement for Relatively Narrow and Wide QRS Complexes After Cardiac Resynchronization Therapy for Heart Failure
Authors: YU CHEUK‐MAN , FUNG JEFFREY WING‐HONG , CHAN CHI‐KIN , CHAN YAT‐SUN , ZHANG QING , LIN HONG , YIP GABRIEL W.K. , KUM LEO C.C. , KONG SHUN‐LING , ZHANG YAN , SANDERSON JOHN E.
Published: September 2004

Introduction: Cardiac resynchronization therapy (CRT) has been shown to reverse left ventricular (LV) remodeling and improve symptoms in heart failure patients with wide QRS complexes; however, its role in patients with mildly prolonged QRS complexes is unclear. This study investigated if CRT benefited patients with mildly prolonged QRS complexes >120 to 150 ms and explored if the severity of systolic asynchrony determined such a response.

Methods and Results: Fifty‐eight patients (age 66 ± 11 years, 66% male) who had undergone CRT were studied prospectively. Of these patients, 27 had QRS duration between 120 and 150 ms (group A), and 31 had QRS duration >150 ms (group B). Tissue Doppler echocardiography and clinical assessment were performed at baseline and 3 months after CRT. Both groups had significant reduction of LV volume and increased ejection fraction, +dP/dt, and sphericity index (all P < 0.05). These improvements were greater in group B and were explained by the higher prevalence of systolic intraventricular asynchrony. Significant reverse remodeling (reduction of LV end‐systolic volume >15%) was evident in 46% of group A patients and 68% of group B patients. Improvement in clinical endpoints was observed in both groups (all P < 0.01), although the changes in metabolic equivalent and New York Heart Association functional class were greater in group B. In both groups, systolic asynchrony index (TS‐SD) was the most important predictor of reverse remodeling (r =−0.78, P < 0.001) and was the only independent predictor in the multivariate model (β=−1.80, confidence interval =−2.18 to −1.42, P < 0.001); QRS duration was not. A predefined TS‐SD value >32.6 ms had a sensitivity of 94% and specificity of 83% to predict reverse remodeling. Improvement of intraventricular asynchrony after CRT was evident only in responders (P = 0.01).

Conclusion: Improvement of LV remodeling and clinical status is evident after CRT in heart failure patients with QRS duration >120 to 150 ms. These responders are closely predicted by the severity of prepacing intraventricular asynchrony but not QRS duration.
Transient Marangoni convection in hanging evaporating drops
Authors: Savino R. , Fico S.
Published: September 2004

A combined experimental and numerical analysis has been carried out to study Marangoni effects during the evaporation of droplets. The experiments are performed with pendant drops of silicone oils (with different viscosities) and hydrocarbons. The temperature of the disk sustaining the drop is rapidly increased or decreased in order to study transient heating or cooling processes. The velocity field in the droplet is evaluated monitoring the motion of tracers in the meridian plane, using a laser sheet illumination system and a video camera. Surface temperature distributions of the drops are detected by infrared thermocamera. The numerical model is based on axisymmetric Navier–Stokes equations, taking into account the presence of Marangoni shear stresses and evaporative cooling at the liquid-air interface. Marangoni flows cause a larger, more uniform surface temperature, increasing heat transfer from disk to droplet, as well as evaporation rate. When Marangoni effects are negligible, larger surface temperature differences occur along the drop surface and heat transfer is relatively small. The role of Marangoni and buoyancy flows in silicone oils with different viscosities and hydrocarbons is discussed and correlations are presented between experimental and numerical results.
Assessment of a flame surface density-based subgrid turbulent combustion model for nonpremixed flames of wood pyrolysis gas
Authors: Zhou Xiangyang , Pakdee Watit , Mahalingam Shankar
Published: September 2004

A flame surface density (FSD) model for closing the unresolved reaction source terms is developed and implemented in a large eddy simulation (LES) of turbulent nonpremixed flame of wood pyrolysis gas and air. In this model, the filtered reaction rate ω¯α of species α is estimated as the product of the consumption rate per unit surface area mα and the filtered FSD Σ¯. This approach is attractive since it decouples the complex chemical problem (mα) from the description of the turbulence combustion interaction (Σ¯). A simplified computational methodology is derived for filtered FSD Σ¯, which is approximated as the product of the conditional filtered gradient of mixture fraction and the filtered probability density function. Two models for flamelet consumption rate mα are proposed to consider the effect of filtered scalar dissipation rate. The performance of these models is assessed by direct numerical simulation (DNS) database where a laminar diffusion flame interacts with a decaying homogeneous and isotropic turbulent flow field. The chemistry is modeled by a four-step reduced mechanism that describes the oxidization process of gaseous fuel released from high temperature pyrolysis of wood occurring in a wildland fire. Two-dimensional (2D) and 3D LES computations based on the FSD models are conducted for the same conditions as the DNS. The comparative assessments confirm the applicability of the proposed FSD model to describe the filtered reaction rate and the time evolution of temperature and species concentration in the turbulent nonpremixed flame.