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.

Structural transformation in Ni-bearing Na2Si2O5 glass and melt

Abstract: The coordination environment around Ni at minor concentration levels (2 wt. % NiO) in Na2Si2O5 glass and melt (293–1250K) has been investigated by Ni K-edge X-ray Absorption Fine Structure (XAFS) spectroscopy. X-ray Absorption Near Edge Structure (XANES) spectra indicate that both IVNi and VNi occur in the glass, whereas IVNi is dominant in the melt. The average anharmonic Ni-O distances derived from XAFS spectra of the glass at 293 K and the melt above 1150 K are 2.00 (±0.02) and 1.97 (± 0.02) A, respectively. The Ni-O distance in the glass is consistent with a mixture of IVNi and VNi, whereas that in the melt is consistent with dominantly IVNi, suggesting a Ni-coordination change during glass melting. This major change in Ni coordination indicates significant reorganization of the melt during quenching and crystallization. These observations for a compositionally-simple melt/glass system may help explain the enrichment of Ni in early-formed igneous minerals. They also suggest the possibility of a pressure-induced coordination change around Ni in the mantle which may influence geochemical modeling of the deep Earth.

A Review on Forearc Ophiolite Obduction, Adakite-Like Generation, and Slab Window Development at the Chile Triple Junction Area: Uniformitarian Framework for Spreading-Ridge Subduction

Abstract: This paper aggregates the main basic data acquired along the Chile Triple Junction (CTJ) area (45°–48°S), where an active spreading center is presently subducting beneath the Andean continental margin. Updated sea-floor kinematics associated with a comprehensive review of geologic, geochemical, and geophysical data provide new constraints on the geodynamics of this puzzling area. We discuss: (1) the emplacement mode for the Pleistocene Taitao Ridge and the Pliocene Taitao Peninsula ophiolite bodies. (2) The occurrence of these ophiolitic complexes in association with five adakite-like plutonic and volcanic centers of similar ages at the same restricted locations. (3) The inferences from the cooccurrence of these sub-coeval rocks originating from the same subducting oceanic lithosphere evolving through drastically different temperature–pressure (P–T) path: low-grade greenschist facies overprint and amphibolite-eclogite transition, respectively. (4) The evidences that document ridge-jump events and associated microplate individualization during subduction of the SCR1 and SCR-1 segments: the Chonos and Cabo Elena microplates, respectively. The ridge-jump process associated with the occurrence of several closely spaced transform faults entering subduction is controlling slab fragmentation, ophiolite emplacement, and adakite-like production and location in the CTJ area. Kinematic inconsistencies in the development of the Patagonia slab window document an 11- km westward jump for the SCR-1 spreading segment at*6.5-to-6.8 Ma. The SCR-1 spreading center is relocated beneath the North Patagonia Icefield (NPI). We argue that the deep-seated difference in the dynamically sustained origin of the high reliefs of the North and South Patagonia Icefield (NPI and SPI) is asthenospheric convection and slab melting, respectively. The Chile Triple Junction area provides the basic constraints to define the basic signatures for spreading-ridge subduction beneath an Andean-type margin

Pressure-induced Ge coordination change and polyamorphism in SiO2–GeO2 glasses

Abstract: The pressure-induced coordination change of Ge from fourfold to sixfold coordination state has been studied by in situ high pressure X-ray Absorption Spectroscopy at Ge K-edge, in SiO2–GeO2 tetrahedral framework glasses. The transformation occurs at higher pressure and over a broader pressure range when the SiO2 content increases. A careful analysis of both XANES and EXAFS signals supports a model of a mixing of [4]Ge and [6]Ge states in the transition region, in agreement with a kinetically hindered first-order process for the transformation at room temperature.

Benthic geochemistry of manganese in the Bay of Biscay, and sediment mass accumulation rate

Abstract: Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations, Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles, but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant. This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized. The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV) species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate. The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides or sediment traps. The method has also been validated with data collected in other marine sedimentary environments.

High-power CW linearly polarized all-fiber Raman laser

Abstract: We demonstrate a high-power continuous-wave linearly polarized all-fiber Raman laser. The maximum Stokes output power of 4.7 W at 1120-nm wavelength with conversion slope efficiency of 87% was achieved. It is shown that Raman laser threshold greatly depends on pump polarization degree while Raman laser polarization depends on the design of Raman converter rather than on polarization of the pump laser. Slope efficiency was found to be independent on pump polarization degree.