IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Detecting atmospheric perturbations produced by Venus quakes

Abstract: [1] The possibility to detect seismic activity on Venus by using the mechanical coupling of the solid-atmosphere system is investigated. First, the atmospheric attenuation of infrasonic waves produced by quakes is theoretically determined from a pure CO2 atmospheric model, demonstrating that frequencies below 0.1 Hz are amplified by a factor of 10 000 above 120 km altitude. With a simple quake model, an upper limit of infrasonic adiabatic temperature and density perturbations above the source is estimated. Then, we demonstrate that the temperature increase due to high altitude acoustic energy dissipation above a quake is large enough to be measured by remote sensing methods. Finally, the expected post-seismic effects are analyzed in the framework of the VIRTIS instrument on board the ESA Venus Express mission.

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.

Deformation Mechanisms of Antigorite Serpentinite at Subduction Zone Conditions Determined from Experimentally and Naturally Deformed Rocks

Abstract: We performed deformation-DIA experiments on antigorite serpentinite at pressures of 1–35 GPa and temperatures of between 400 and 650 °C, bracketing the stability of antigorite under subduction zone conditions For each set of pressure–temperature (P–T) conditions, we conducted two runs at strain rates of 5 × 10 − 5 and 1 × 10 − 4 s − 1 We complemented our study with a sample deformed in a Griggs-type apparatus at 1 GPa and 400 °C ( Chernak and Hirth, 2010 ), and with natural samples from Cuba and the Alps deformed under blueschist/eclogitic conditions Optical and transmission electron microscopies were used for microstructural characterization and determination of deformation mechanisms Our observations on experimentally deformed antigorite prior to breakdown show that deformation is dominated by cataclastic flow with observable but minor contribution of plastic deformation (microkinking and (001) gliding mainly expressed by stacking disorder mainly) In contrast, in naturally deformed samples, plastic deformation structures are dominant (stacking disorder, kinking, pressure solution), with minor but also perceptible contribution of brittle deformation When dehydration occurs in experiments, plasticity increases and is coupled to local embrittlement that we attribute to antigorite dehydration In dehydrating samples collected in the Alps, embrittlement is also observed suggesting that dehydration may contribute to intermediate-depth seismicity Our results thus show that semibrittle deformation operates within and above the stability field of antigorite However, the plastic deformation recorded by naturally deformed samples was likely acquired at low strain rates We also document that the corrugated structure of antigorite controls the strain accommodation mechanisms under subduction conditions, with preferred inter- and intra-grain cracking along (001) and gliding along both a and b We also show that antigorite rheology in subduction zones is partly controlled by the presence of fluids, which can percolate within the exhumation channel via deformation-induced interconnected porosity

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.

Kerr-lens mode-locked femtosecond polycrystalline Cr 2+ :ZnS and Cr 2+ :ZnSe lasers

Abstract: We report the first Kerr-lens mode-locked polycrystalline Cr2+:ZnS and Cr2+:ZnSe lasers, with pulse duration of 125 fs at a pulse repetition rate of 160 MHz, emitting around 2.3 – 2.4 µm. The mode-locked lasers were pumped by a radiation of 1550 nm Er-fiber amplifier seeded by semiconductor laser. The long-term stable Kerr-lens mode-locked laser operation with the output power of 30 mW (Cr2+:ZnS) and 60 mW (Cr2+:ZnSe) was obtained. We also demonstrate amplification of the fs laser pulse train in a cw pumped single-pass polycrystalline Cr2+:ZnS laser amplifier.