Showing papers by "IPG Photonics published in 2002"

Morphology, displacement, and slip rates along the North Anatolian Fault, Turkey

Abstract: [1] Geological and geomorphological offsets at different scales are used to constrain the localization of deformation, total displacement, and slip rates over various timescales along the central and eastern North Anatolian Fault (NAF) in Turkey The NAF total displacement is reevaluated using large rivers valleys (80 ± 15 km) and structural markers (Pontide Suture, 85 ± 25 km; Tosya-Vezirkopru basins, 80 ± 10 km) These suggest a Neogene slip rate of 65 mm/yr over 13 Myr The river network morphology shows offsets at a range of scales (20 m to 14 km) across the main fault trace and is also used to estimate the degree to which deformation is localized At a smaller scale the morphology associated with small rivers is offset by 200 m along the NAF The age of these features can be correlated with the Holocene deglaciation and a slip rate of 18 ± 35 mm/yr is determined This is consistent with a rate of 18 ± 5 mm/yr deduced independently from the 14C dating of stream terrace offsets Over the short term, GPS data gives a similar rate of 22 ± 3 mm/yr All our results tend to show that most of the deformation between the Anatolian and Eurasian lithospheric plates has been accommodated along, or very close to, the active trace of the NAF The difference between the Neogene and the Holocene slip rate may be due to the recent establishment of the current plate geometry after the creation of the NAF

Magnetic properties of variably serpentinized abyssal peridotites

Abstract: We have compiled new and published data on the magnetic properties of 245 serpentinized abyssal peridotites from seven Deep Sea Drilling Project and Ocean Drilling Program sites. The magnetic susceptibility (K) of these samples does not increase linearly with the degree of serpentinization (S). Instead, K remains modest in partially serpentinized samples (S 75%) peridotites in the oceanic crust. Moderately serpentinized peridotites (S < 75%) have NRM values <5 A/m and K < 0.05 SI. Low-temperature oxidation of magnetite is found to lower the NRM and K values of seafloor samples and of cataclastically deformed drilled samples.

The 26 December (Boxing Day) 1997 sector collapse and debris avalanche at Soufrière Hills Volcano, Montserrat

Abstract: The southern sector of Soufriere Hills Volcano failed on 26 December 1997 (Boxing Day), after a year of disturbance culminating in a devastating eruptive episode. Sector collapse produced a c. 50 x 10 6 m 3 volcanic debris avalanche, and depressurized the interior of the lava dome, which exploded to generate a violent pyroclastic density current. The south-directed growth of a lava lobe and build-up of lava-block talus, since early November 1997, brought the hydrothermally weakened sector to a condition of marginal stability. Limit-equilibrium stability analyses and finite-difference stress-deformation analyses, constrained by geomechanical testing of edifice and debris avalanche materials, suggest that the sector collapse was triggered by a pulse of co-seismic exogenous lava shear-lobe emplacement. Slip-surface localization was influenced by strain-weakening. The source region fragmented into avalanche megablocks, and further disruption generated a chaotic avalanche mixture that included variably indurated and coloured hydrothermally altered material, and much talus. The avalanche consisted of several flow pulses that reflected complexities of source disruption and channel topography. In the proximal zone, within 1.5 km from source, many megablocks preserve pre-collapse stratigraphy. At major bends the avalanche separated into channelled and overspill flows. In the distal region, 15°), consistent with geotechnical test data and the localized presence of pore-water pressures. The best-fit model suggests an emplacement time >3 minutes and a typical maximum velocity of about 40ms _1 , which are consistent with field estimates.

First-principles calculation of the infrared spectrum of hematite

Abstract: The theoretical infrared spectrum of lizardite [Mg3Si2O5(OH)4] was computed using first-principles quantum mechanical calculations. Density functional perturbation theory allowed us to derive the low-frequency dielectric tensor of lizardite as a function of the light frequency. The infrared spectrum was then calculated using a model that takes into account the platy shape of particles. A very good agreement was obtained between theory and experiment. This agreement allows us to make an unambiguous assignment of the major absorption bands observed in the IR spectrum of lizardite, including the stretching bands of OH groups.

Preavalanche instabilities in a granular pile.

Abstract: We investigate numerically the transition between static equilibrium and dynamic surface flow of a 2D cohesionless granular system driven by a continuous gravity loading. This transition is characterized by intermittent local dynamic rearrangements and can be described by an order parameter defined as the density of critical contacts, i.e., contacts where the friction is fully mobilized. Analysis of the spatial correlations of critical contacts shows the occurrence of "fluidized" clusters which exhibit a power-law divergence in size at the approach of the stability limit. The results are compatible with recent models that describe the granular system during the static/dynamic transition as a multiphase system.

Presence of sulfite (SIV) in arc magmas: Implications for volcanic sulfur emissions

Abstract: [1] The outstanding production of sulfur dioxide at arc volcanoes is not satisfactorily explained by most of the geochemical models involving the magmatic redox conditions. It is commonly accepted that sulfur is transported mainly as sulfide (SII−) and/or sulfate (SVI) by mantle-derived melts, before being released as SO2 and/or H2S in volcanic emissions. We present the first experimental evidence that other S-species coexist in water-rich arc basalts, by using X-ray microspectroscopy of olivine-hosted melt inclusions. In particular, we propose a new model involving sulfite (SIV) as the intermediate species dissolved in basaltic melts which results in highly efficient partitioning of sulfur into volcanic gas emissions at the origin of excess sulphur degassing observed at arc basaltic volcanoes.

135W CW fiber laser with perfect single mode output

Abstract: Reliable 135 W CW ytterbium doped fiber laser has been demonstrated with measured M/sup 2/ < 1.05. The stimulated Raman scattering imposed the major limit on the output power. No thermal distortions or damage of the fiber core was observed.

EXAFS evidence of sorbed arsenic(V) and pharmacosiderite in a soil overlying the Echassières geochemical anomaly, Allier, France

Abstract: At Echassieres (Allier, France), arsenic speciation was determined in a soil developed over a micaschist where Hercynian hydrothermal mineralization, including arsenopyrite FeAsS and lollingite FeAs2, has lead to a regional As anomaly. The overlying soils which have developed from long term weathering exhibit As levels as high as 900 ppm in the richest area, where the saprolite contains up to 5200 ppm As. Analysis by powder XRD, [nu]-X-ray diffraction on the 20[nu]m scale, SEM-EDS and electron micro-probe analyses revealed that As, released from arsenopyrite and/or lollingite alteration, is concentrated in a secondary iron arsenate, pharmacosiderite, (Bax,K2-2x) (Fe,Al)4 (AsO4)3 (OH)5 · 6H2O. Quantitative mineralogical analysis by Rietveld refinement indicates that the proportion of As hosted by this mineral decreases systematically from the saprolite to the topsoil (from 70 % to 30 % of the total bulk As content, respectively). EXAFS spectroscopy indicates that the main form of the As occurring with pharmacosiderite, consists of As(V) ions sorbed on iron oxides. Sorption processes, which dominate As speciation in the topsoil horizons, appear as a key mechanism able to delay As dissemination from soils to plant and surface waters, provided that pH and Eh conditions remain sufficiently acidic and oxidizing, respectively.

Polyphased uplift and erosion of the Cévennes (southern France). An example of slow morphogenesis

Abstract: The Cevennes are bordering the French Massif Central and the Gulf of Lion margin. The morphogenesis of this area results from an interaction between deep-seated and superficial processes, whose origin and timing is still discussed. We attempt a reconstruction of the surrection and erosion history of the area through a multidisciplinary approach including geology, geomorphology, thermochronology and geochronology. Thermochronology shows that the Cevennes basement underwent some 2 km denudation in mid-Cretaceous time. Analyses of the sediments preserved on uplifted surfaces and in peripheral sedimentary basins indicate a differential surface uplift of the Cevennes, of the surrounding calcareous plateaus, and of the coastal plain, that occurred in several stages during the Tertiary. Early Miocene rifting of the Gulf of Lion margin and opening of the NW Mediterranean drastically modified the drainage network. Geomorphology analyses of the incised rivers and karst network suggest that most of the incision results from uplift that occurred sometime in the Serravalian-Tortonian interval. U/Th dating of calcite concretions in karsts allows to chronologically bracket the formation of some fluvial terraces, and to find very low incision rates during the Pleistocene. Most of the morphogenesis predates the Quaternary. This ongoing study shows an example of polyphased and very slow morphogenesis, with present-day landscape including elements as old as Cretaceous.

Longitudinal permeability of spatially periodic rectangular arrays of circular cylinders. I. A single cylinder in the unit cell

Abstract: We study the longitudinal permeability of a spatially periodic rectangular array of circular cylinders, when a Newtonian fluid is flowing at low Reynolds number along the cylinders. The longitudinal component of the velocity obeys a Poisson equation which is transformed into a functional equation. This equation can be solved by the method of successive approximations. The major advantage of this technique is that the permeability of the array can be expressed analytically in terms of the radius of the cylinders and of the aspect ratio of the unit cell.

Heat capacity and entropy of rutile (TiO 2 ) and nepheline (NaAlSiO 4 )

Abstract: From heat capacities measured adiabatically at low temperatures, the standard entropies at 298.15 K of synthetic rutile (TiO2) and nepheline (NaAlSiO4) have been determined to be 50.0 ± 0.1 and 122.8 ± 0.3 J mol−1 K, respectively. These values agree with previous measurements and in particular confirm the higher entropy of nepheline with respect to that of the less dense NaAlSiO4 polymorph carnegieite.

Nature and properties of suspended solids in the Amazon Basin

Abstract: francaisCette etude porte sur l'analyse de fractions particulaire (> 0,2 [nu]m) et colloidale (0,2 [nu]m-5kD) issues de fleuves du Bassin amazonien (Bresil) : Rio Solimoes et Amazonas, Rio Negro, Rio Branco et Rio Trombetas. Les echantillonnages ont ete effectues lors de missions du programme Hibam en septembre 1997 et 1998 (periode de decrue). Plusieurs outils ont ete mis en oeuvre, comprenant la spectroscopie infrarouge a transformee de Fourier (IR-TF), la spectroscopie de resonance paramagnetique electronique (RPE) et des mesures potentiometriques. Les principaux objectifs etaient de determiner les signatures specifiques des solides en suspension en relation avec leur nature et reactivite, et de discuter des potentialites de cette approche pour tracer leur source et evolution. Une attention particuliere a ete apportee au prelevement et a la recuperation des solides en suspension, notamment pour concentrer les colloides et minimiser les artefacts de preparation. Les matieres particulaires et colloidales sont respectivement de nature organo-minerale et organique. En accord avec la mineralogie, les signatures spectroscopiques des fractions particulaires distinguent les Rio Amazonas et Solimoes des rivieres du nord du Bassin amazonien. Dans ces dernieres, les kaolinites representent les argiles dominantes et montrent des caracteristiques cristallo-chimiques proches telles que le degre de desordre cristallin, malgre l'extension des surfaces drainees et les contrastes couramment observes dans les profils d'alteration. Dans tous les fleuves etudies, les colloides montrent des signatures IR-TF similaires, caracteristiques de substances humiques. Au contraire, la RPE revele differentes especes paramagnetiques qui permettent de distinguer qualitativement et quantitativement les colloides : fer trivalent present sous forme de complexes organiques et oxydes au sens large, manganese divalent et radicaux libres organiques. Les contrastes observes semblent herites des processus d'alteration agissant dans les principales regions pedoclimatiques drainees par les fleuves etudies. Les mesures potentiometriques des fractions colloidales montrent une reactivite de type substance humique en accord avec des fonctions carboxyliques et phenoliques, dont les contributions respectives differencient Rio Negro et Rio Solimoes/Amazonas. EnglishSuspended solids from several rivers of the Amazon Basin (Brazil) have been studied in both the particulate (> 0,2 ?m) and colloidal (0.2 ?m-5kD) fractions through a combination of tools including Fourier transform infrared spectroscopy (FT-IR), electron paramagnetic resonance (EPR) and potentiometric measurements. Particulate and colloidal matter are organo-mineral and organic, respectively. Signatures of the particulate fractions distinguish Rio Amazonas/Rio Solimoes rivers and the northern basin rivers (Rio Negro, Rio Branco, Rio Trombetas). In the latter, kaolinites are the dominant clays and exhibit close crystal chemistry characters such as degree of disorder. FT-IR of colloids exhibits similar signatures of humic substances in all rivers. By contrast, EPR reveals various species which qualitatively and quantitatively differentiate the riverborne colloids: trivalent iron occurring as specific complexes with organic functional groups or as oxides sensu lato, divalent manganese, organic free radicals. The observed differences may be inherited from the weathering processes working in the main pedoclimatic regions drained by the studied rivers. Insights from potentiometric measurements of the recovered colloids also evidence a humic like reactivity consistent with carboxyl and phenol moieties, the relative contributions of which differentiate the Rio Negro and Rio Solimoes/Amazonas.

Separation of P- and SV-wavefields from multi-component seismic data in the τ − p domain

Abstract: Summary Multi-component seismic data contain richer information about the elastic parameters of the subsurface than do conventional single-component data. Separation of the compressional and shear wavefields from multi-component seismic data is crucial in estimating the subsurface elastic properties. We present a τ−p domain scheme to separate P- and SV-wavefields from multi-component seismic data observed at the free surface and ocean bottom. Based on plane-wave components with known horizontal slowness in τ−p domain, the whole P- and SV-wavefields are separated into the direction of observed P- and SV-wave oscillations, by rotation of the horizontal and vertical components respectively. The incident P- and SV-waves are extracted from the separated wavefields using plane wave partitions at the free surface and ocean bottom. The parameters used in the separation are the local seismic wave velocities and the density at the receiver location. Numerical tests on synthetic data for plane-layered models show good performance and accuracy of the scheme.

Hazard implications of small-scale edifice instability and sector collapse: a case history from Soufrière Hills Volcano, Montserrat

Abstract: During the 1995 to 1998 phase of dome growth at Soufriere Hills Volcano on Montserrat, we documented instability of the steep southern rim of English9s Crater, known as Galway9s Wall. The horseshoe-shaped English9s Crater provided good evidence for previous sector collapses, and assessments undertaken in late 1996 anticipated the possibility of a partial sector collapse and a SW-directed explosion, hazards previously unrecognized on Montserrat. A change from predominantly endogenous to exogenous growth of the lava dome at the end of 1996 eased the stress on the southern sector. However, rapid dome growth in November and December 1997 led to severe reloading and eventual sector failure at the base of the buried Galway9s Wall and in the adjacent hot-spring area. This failure resulted in the debris avalanche and lateral blast of 26 December 1997. Similar sector collapses at a number of small volcanoes in the Caribbean, as well as worldwide, are evidence that edifice instability develops commonly in dome-forming eruptions. The hazards from a sector collapse and a consequent lateral blast are extreme, and monitoring operations and disaster planning at such volcanoes should focus on these, as well as on the more common hazards of conventional pyroclastic flows associated with dome growth.

High Precision Hf‐W Isotopic Measurements in Meteoritic Material Using Negative Thermal Ionisation Mass Spectrometry (NTIMS)

Abstract: This paper presents a two-stage anion-exchange procedure for tungsten extraction, an improved mass spectrometric procedure for tungsten analysis and a simplified chemical separation and TIMS procedure for the determination of Hf concentrations. The chemical separation of tungsten is based on its complexing properties with HF and H2O2. The blank level for a sample size of 300 mg is about 80 pg for tungsten. The procedure is designed for the high sensitivity of negative thermal ionisation mass spectrometry (NTIMS) provided by the use of Mg oxide as an emitter on Ir filaments. Tungsten can be readily measured with a high precision in various meteoritical material and especially in small W-poor silicate fractions. Samples containing as little as a few ng g-1 tungsten can be analysed reliably with this method. Cet article presente une procedure ďextraction du tungstene en deux etapes sur resine echangeuse ďanions, une procedure amelioree de spectrometrie de masse pour ľanalyse du tungstene, et une separation chimique simplifiee ainsi qu'une methode ďanalyse par TIMS pour determiner les concentrations en Hf. La separation du tungstene est basee sur ses proprietes complexantes vis-a-vis de HF et H2O2. Le blanc de procedure pour des echantillons de 300 mg est de 80 pg de tungstene environ. La procedure est optimisee pour beneficier de la grande sensibilite de la spectrometrie de masse a thermo-ionisation negative (NTIMS) resultant de ľutilisation ďun activateur a base ďoxyde de magnesium sur un filament ďiridium. Le tungstene peut ainsi etre mesure avec une grande precision dans divers materiaux meteoritiques et en particulier dans de petites fractions silicatees pauvres en W. Des echantillons contenant seulement quelques ng g-1 de tungstene peuvent etre analyses de facon fiable avec cette methode.

1.6 Tbit/s (40/spl times/42.7 Gbit/s) transmission over 3600 km UltraWave/spl trade/ fiber with all-Raman amplified 100 km terrestrial spans using ETDM transmitter and receiver

Abstract: We demonstrate error free transmission of 40/spl times/40 Gbit/s over a record distance of 36/spl times/100 km UltraWave/spl trade/ dispersion managed fiber with all-Raman amplification and 100 GHz channel spacing CS-RZ modulation and 43 Gbit/s ETDM transmitter and receiver are used

Incorporation of Cr3+ in dickite: a spectroscopic study

Abstract: We have investigated a well-ordered sample of natural Cr-bearing dickite from Nowa Ruda (Lower Silesia, Poland) using electron paramagnetic resonance (EPR) at X- and Q-band frequencies (9.42 and 33.97 GHz, respectively) and optical diffuse reflectance spectroscopy. The observation of the spin-forbidden transitions at 15500 and 14690 cm−1 allows us to unambiguously identify the major contribution of octahedrally coordinated Cr3+ ions in the optical spectrum. The X- and Q-band EPR spectra show two superposed Cr3+ signals. The corresponding fine-structure parameters were determined at room temperature and 145 K. These results suggest the substitution of Cr3+ for Al3+ in equal proportions in the two unequivalent octahedral sites of the dickite structure. In kaolin group minerals, the distortion around Cr3+ ions (λ≈ 0.2–0.4) in Al sites is significantly less rhombic than that observed around Fe3+ ions (λ≈ 0.6–0.8).

Precision spectral sculpting for narrow-band amplification of broadband frequency-modulated pulses.

Abstract: Amplification of broadband frequency-modulated (FM) pulses in high-efficiency materials such as ytterbium-doped strontium fluorapatite results in significant gain narrowing, leading to reduced on-target bandwidths for beam smoothing and to conversion from frequency modulation to amplitude modulation (AM). To compensate for these effects, we have applied precision spectral sculpting, requiring both amplitude and phase shaping, to the amplification of broadband FM pulses in narrow-band gain media. We have demonstrated sculpting for centerline small-signal gains of 104, producing amplified pulses that have both sufficient bandwidths for on-target beam smoothing and temporal profiles that have no potentially damaging AM.

Longitudinal permeability of spatially periodic rectangular arrays of circular cylinders II. An arbitrary distribution of cylinders inside the unit cell

Abstract: We study the longitudinal permeability of unidirectional disjoint circular cylinders, when a Newtonian fluid is flowing at low Reynolds number along these cylinders; the longitudinal velocity satisfies the Poisson equation. The cylinders are arranged according to a doubly periodic structure. The number of cylinders in each rectangle can be arbitrary as well as their positions and radii. The method of functional equations yields analytical formulae for permeability in terms of these quantities. These formulae are written also in continuous form to study the flow for large numbers of cylinders. Special attention is paid to the case of the square unit cell, equal radii and lognormal distribution of radii.

Manganese accommodation in fossilised mastodon ivory and heat-induced colour transformation Evidence by EXAFS

Abstract: Odontolite or bone turquoise, a turquoise-blue coloured heated fossilised mastodon ivory or bone, is an imitation of the mineral turquoise used for the decoration of medieval art objects. Its colour origin can be ascribed to Mn 5+ traces in a tetrahedral environment of four oxygen atoms in an apatite matrix. The structural environment of Mn was investigated by means of extended X-ray absorption fine structure (EXAFS) in order to shed new light on the colour transformation of fossilised ivory induced by a thermal treatment. This was particularly difficult as the manganese concentration does not exceed trace amounts in fossilised ivory. EXAFS experiments confirm the presence of Mn 2+/3+/4+ ions before and Mn 5+ ions after thermal treatment in fossilised ivory and the location of Mn 5+ ions on a P analogous site in apatite.

Renormalization of QED in an external field

Abstract: The Schwinger equations of QED are rewritten in three different ways as integral equations involving functional derivatives, which are called weak field, strong field, and SCF quantum electrodynamics. The perturbative solutions of these equations are given in terms of appropriate Feynman diagrams. The Green function that is used as an electron propagator in each case is discussed in detail. The general renormalization rules for each of the three equations are provided both in a non perturbative way (Dyson relations) and for Feynman diagrams.

Seismological and mineralogical constraints on the inner core fabric

Abstract: [1] Under the assumption of lattice preferred orientation of iron hcp crystals, the seismic anisotropy of the inner core is related to single crystal elastic properties by a fabric model. This model is able to explain a new seismological constraint: the constant behaviour of the ratio k of two anisotropy coefficients, despite radial and lateral variations of the anisotropy level in the inner core. The relevance of the theoretical calculations of iron single crystal elastic properties at inner core conditions are tested by a comparison between seismic estimates and computed values of this ratio k. Taking into account the error bar of the seismic estimate, iron hcp structures presenting fast and slow c axis could fit the data equally well.

Schwarz Problem for Multiply Connected Domains and its Application to Diffusion Around Fractals

Abstract: Stationary diffusion perpendicular to unidirectional circular cylinders arranged in two-dimensional fractals set is considered. Complex potentials and the method of functional equations are used to determine the concentration field. This result is applied to the calculation of the effective diffusion tensor of fractals randomly diluted on the plane. In particular, we discuss a special fractal derived by a group of Mobius transformations and deduce a generalization of the Clausius-Mossotti approximation.